Histology Flashcards
What colour does PAS stain sugars?
Deep magenta
What colour does alcian blue stain mucins?
Blue
What colour does H&E stain nuclei and cytoplasm?
Nuclei - Blue
Cytoplasm - Pink
What shape are smooth muscle cells?
Fusiform
What are columnar cells?
Epithelial cells which are taller than they are wide
What are squamous cells?
Flattened plate-like cells
Where does DNA transcription occur?
The nucleolus
What 2 things happen in the outer membrane of the mitochondria?
- Lipid synthesis
- Fatty acid metabolism
What happens in the inner membrane of the mitochondria?
Respiratory chain ATP production
What happens in the matrix of the mitochondria?
TCA (Kreb’s) cycle
What happens in the inter membranous space of the mitochondria?
Nucleotide phosphorylation (ADP to ATP)
What is the lifespan of erythrocytes?
120 days
What is chromatin?
Nuclear DNA and proteins
What happens in the RER?
Protein synthesis
What happens in the SER?
Membrane lipid is formed
What happens in the Golgi apparatus?
Formation of complex oligosaccharides, protein phosphorylation and proteolysis
What is the filament with the smallest diameter?
Actin
Name a microfilament
Actin
Name a microtubule
Tubulin
Name 3 intermediate filaments
Desmin, nuclear laminin and vimentin
Name the three filaments in increasing size
Microfilament, intermediate filament, microtubules
What is the intermediate filament mainly found in muscle?
Desmin
Where are cytokeratins (intermediate filaments) found?
Epithelial cells
Where are desmin (intermediate filaments) found?
Myocytes
Where are Glial fibrillary acidic protein (intermediate filaments) found?
Astrocytic glial cells
Where are Neurofilament protein (intermediate filaments) found?
Neurons
Where are nuclear laminin (intermediate filaments) found?
Nuclei of all cells
Where are vimentin (intermediate filaments) found?
Mesodermal cells
What is lipofuscin?
A wear and tear pigment formed by per oxidation of membrane lipids
What is haemosiderin?
An iron-containing brown pigment
What is melanin?
A brown pigment produced by melanocytes in skin (and elsewhere)
What is rhodopsin?
A pigment found in the retina
How is simple squamous epithelium formed?
By flattened epithelial cells resting on a basement membrane
What is endothelium?
An epithelium which lines the inside of blood vessels?
What is mesothelium?
An epithelium which lines the outside of the lungs
What is peritoneum?
An epithelium which lines the abdominal organs
What are the two features of columnar epithelium?
- Cells are taller than they are wide
- May have projections such as cilia/microvilli
Do all epithelial compromise of nucleated cells?
Yes
What is a possible feature of simple columnar epithelium?
Microvilli on luminal surface
What is the epithelium of the Fallopian tube?
Columnar ciliated epithelium
What does respiratory epithelium consist of?
Pseudostratified columnar ciliated epithelium containing admixed goblet cells
Where is respiratory epithelium found?
The conducting airways:
- Nasopharynx
- Nasal sinuses
- Trachea
- Bronchi
- Bronchioles
What are the two proteins which are involved in ciliary movement?
- Tubulin
- Dynein
Name two non-contractile proteins
- Collagen
- Elastin
Name two contractile proteins which are found in muscle cells
- Actin
- Myosin
Name one feature of urothelium
It is waterproof
What type of epithelium is urothelium?
Complex stratified epithelium with a pseudo stratified component beneath a surface layer of umbrella cells that aren’t in contact with the basement membrane
What is the purpose of umbrella cells in urothelium?
Make the epithelium waterproof
Name 4 places where the urothelium lines
- Renal pelvis
- Ureters
- Urinary bladder
- Urethra
What does PAS help highlight?
Basement membranes
Name things which basement membranes consist of
Type IV collagen and fibronectin
What is the function of desmosomes?
Help spread mechanical forces across cells and their neighbours, and anchor cells together
What is the function of hemidesmosomes?
Bind the basal cell layer to the basement membrane
What is holocrine secretion?
When a gland secretes by shedding individual cells
Where is merocrine secretion?
Release of cell products by exocytosis from apical cell surface
What is apocrine secretion?
Involves pinching off part of the apex of the cell
Name 3 types of exocrine secretion
- Holocrine
- Merocrine
- Apocrine
What is endocrine secretion?
Release of products from the cell base into the bloodstream
What are monocytes derived from?
Haematopoietic stem cells
What cells are derived from mesenchymal cells?
Fibroblasts, fat cells and most cartilage/bone cells
What cells are from the haemopoietic stem cell line?
Monocytes, macrophages, lymphocytes, mast cells and blood cells
What substance is found in the walls of elastic arteries?
Elastin
What do fibroblasts produce?
Elastin and collagen
Name 3 visible extracellular fibres
- Reticulin
- Collagen
- Elastin
Name 2 invisible fibres
- Fibronectin
- Laminin
What is tropocollagen?
A triple helix of peptides
What secretes tropocollagen subunits?
Fibroblasts
Where is type I collagen found?
Skin
Where is type II collagen found?
Cartilage
Where is type III collagen found?
Liver, bone marrow and spleen (reticulin)
Where is type IV collagen found?
Basement membranes
Where is type V collagen found?
Placenta
What kind of cartilage is found in the epiglottis?
Elastic
Name 2 places where fibrous cartilage can be found?
- Symphysis pubis
- Intervertebral discs
Name 2 places where hyaline cartilage can be found?
- Part of the nasal septum
- The knee joint
What is the structure of fat inside the white adipose tissue?
- Single, large non membrane-bound globules of lipid in each cell
- Pushes the nuclei to the edges of cells
What is one of the differences between brown and white adipocytes?
- White has one big globule
- Brown has multiple fat globules
What is the primary function of brown adipose tissue?
Heat generation
Where is brown adipose mainly found in adults?
Between shoulder blades
Where is brown adipose mainly found in neonates?
Neck, back, around the aorta and the kidneys
What is the structure of the tendons or ligaments?
Dense regular fibrous connective tissue
Which connective tissue has collagen fibres running in the same direction?
Dense regular connective tissue
What is the connective tissue in the penile fascia?
Dense irregular connective tissue
What is the connective tissue in the adventitia of arteries?
Loose irregular connective tissue
What is the connective tissue in the dermis?
Dense and loose irregular connective tissue
What is the muscular layer of the uterus and what muscle type is it?
Myometrium - smooth muscle
Name two elastic arteries in the body
Aorta and pulmonary artery
Name two muscular arteries in the body
Radial and splenic
What is the feature of muscular arteries?
The media compromises of smooth muscle with very little elastin
Name one component which veins lack
External elastic lamina
What are the layers of the arteries, from inside out?
- Endothelium
- Intima
- Internal elastic lamina
- Media
- External elastic lamina
- Outer adventitia
How is the diameter of capillaries regulated?
By pericytes
What are pericytes?
Contractile cells which wrap around the outside of capillaries and regulate capillary diameter
What is the structure of capillaries?
Compromise of endothelial cells resting on a basement membrane. They don’t have an intima, media or adventitia
Where may capillaries be fenestrated?
The kidney or liver
What are fenestrations?
Gaps in the endothelial layer
Give 3 characteristics of lymphatic vessels
- Contain valves
- Poorly developed elastic laminae
- Thin media, making them similar to veins
Name two things which cartilage lacks
Blood vessels and lymphatics
Where is endometrium present?
Between individual axons
Where is perineurium present?
Surrounds the groups of axons to form fascicles
Where is epineurium present?
Binds fascicles together to form nerve fibres
Which cells produce myelin?
Schwann cells
How do Schwann cells produce myelin?
By repeatedly wrapping itself around part of an axon
What does myelin compromise of?
Multiple layers of Schwann cell membrane
What is a Node of Ravier?
A gap between two Schwann cells on a single axon. The axon is in tact but there is no myelin at this site
What are Schmidt-Lanterman incisures?
Small pockets of cytoplasm left behind during the Schwann cell myelination process
How many axons are myelinated by a single Schwann cell?
1
In unmyelinated axons, how many axons are supported by a single Schwann cell?
Many
Define motor neuron
Cell bodies in grey matter of spinal cord
Define sensory neuron
Cell bodies in dorsal root ganglion
Define sympathetic neuron
Cell bodies in grey matter of cord and in adjacent sympathetic ganglia
Define parasympathetic neuron
Cell bodies in brain and basal ganglia
What percent of the blood is made up of white blood cells?
1%
What is the fluid in blood?
Plasma (or serum if the clotting factors have been removed)
What percentage of the blood is the plasma?
56%
What percentage of the blood consists of the red blood cells?
43%
What percentage of the blood does the white cells and platelets consist of?
1%
What is plasma?
Serum + clotting factors
What is the pattern of formation of erythrocytes?
- First formed in the yolk sac
- Then formed in the liver
- The formed in the bone marrow
Where is haematopoiesis confined to?
- Marrow of flat bones
- Proximal ends of the humeri/femurs
Where are erythrocytes destroyed?
Liver and spleen
What are the predominant leukocytes?
Neutrophils
What is the function of eosinophils?
Help defend against parasitic infections. There numbers increase when there is a parasitic infection
Where do B lymphocytes mature in adults?
Bone marrow
Name two cells which have receptors to IgE and the significance of this
- Basophils and Eosinophils
- They are antagonistic in function
Which cell produces histamines?
Basophils
Which cells counter the action of histamine?
Eosinophils
Name 3 cells in the immune system which are phagocytic
- Eosinophils
- Neutrophils
- Monocytes
Which cells secrete antibodies?
Plasma cells
What is the most abundant leucocyte?
Neutrophils
Name 1 cell of the immune system which doesn’t have IgE receptors
Neutrophils
Which cells become mast cells?
Basophils
Which cells neutralise histamine?
Eosinophils
What cells do monocytes develop into in the liver?
Kupffer cells
What cells do monocytes develop everywhere?
Tissue macrophages and antigen presenting cells
What cells do monocytes develop into in bone?
Osteoclasts
What cells do monocytes develop into in the lungs?
Alveolar macrophages
What are haemocytoblasts?
Multipotential haemopoietic stem cells
What do megakaryocytic give rise to?
Platelets
What are platelets?
Membrane-bound fragments of the cytoplasm of megakaryotes
Where does erythropoiesis occur?
Away from bony trabeculae
What is the basic process of erythropoiesis?
- Cells start basophilic and become eosinophilic
- They gradually lose organelles (as they gain haemoglobin)
- The nucleus stays round and is eventually extruded
- The cells get smaller as they mature
What is the outermost layer of the heart?
Visceral pericardium
What are the layers of the heart (outside in)?
Visceral pericardium, epicardium, myocardium, endocardium
What is the parietal pericardium?
A fibrous sac that contains the heart
Name two layers of the heart which have the same cells
Visceral pericardium and parietal pericardium
What cell type is the pericardium of the heart?
Simple squamous epithelium
What cell type is the pleura and peritoneum of the heart?
Simple squamous epithelium
What is a feature of ventricular cardiac myocyte?
Myofibrils in register (they appear striated)
Name 3 visible extracellular fibres
Reticulin, collagen and elastin
Name 2 invisible extracellular fibres
Fibronectin and laminin
Which collagen type is prevalent in the placenta?
Type V
What is the structure of tropocollagen?
A triple helix of peptides
Where are tropocollagen subunits secreted from?
Fibroblasts
Which collagen type is prevalent in the skin?
Type I
Which collagen type is prevalent in cartilage?
Type II
Which collagen type is prevalent in liver?
Type III
Which collagen type is prevalent in bone marrow?
Type III
Which collagen type is prevalent in the spleen?
Type III (reticulin)
Which collagen type is prevalent in basement membranes?
Type IV
What kind of cartilage does the epiglottis have?
Elastic cartilage
What type of cartilage is found in the symphis pubis and intervertebral discs/
Fibrous cartilage
What type of cartilage does part of the nasal septum and the knee joint have?
Hyaline cartilage
What is the most commonly used dye combination?
H&E
What colour does H&E stain certain cell parts?
Cell nuclei - Blue
Cytoplasm - Pink
Name something other than cytoplasm that stains pink with H&E
Extra-Cellular fibres
What does PAS stain?
Sugars
What does Van Gieson stain?
Elastic
What does alcian blue stain?
Mucins
Name 6 shapes of cells
- Rounded
- Polygonal
- Fusiform
- Squamous (flattened)
- Cuboidal
- Columnar
What type of cells tend to be smaller?
Ones which are less metabolically active
Name 1 cell type which has a lifespan of days
Lining of the gut
Name 3 cell types which have a lifespan of days
Blood, skin and connective tissues
Name 2 cell types which have a lifespan of years
Bones and tendons
Name a cell type which lasts nearly a whole life
Skeletal muscle (limited regeneration)
Name 3 cell types which last a whole life
Nerves/brain, Cardiac muscle and germ cells
Give 3 features of the nucleus
- Brain of the cell
- Double nuclear membrane
- Houses DNA
Give 2 features of the nucleolus
- 1-3 microns in diameter
- Site of rRNA formation
Give 4 features of the mitochondria
- Powerhouses of the cell
- Site of oxidative phosphorylation
- Have their own DNA
- Double membrane
What is the function of the outer membrane of the mitochondria?
Lipid synthesis and fatty acid metabolism
What is the function of the inner membrane of the mitochondria?
Respiratory chain and ATP production
What is the function of the matrix of the mitochondria?
TCA (Krebs’ cycle)
What is the function of the inter membranous space of the mitochondria?
Nucleotide phosphorylation (ADP to ATP)
What is the function and structure of RER?
- Site of protein synthesis
- Highly folded flattened membrane sheets
What is the function and structure of the Golgi apparatus?
- Processes macromolecules synthesised in the ER
- Parallel stacks of membrane
Where is the Golgi apparatus usually prominent?
Plasma cells
What are vesicles and what are they used for?
- Small spherical membrane-bound organelles
- Used for transport, storage and exchanging cell membrane between compartments
What are the function of lysosomes?
Contain acid hydrolyses that degree proteins
What are the function of peroxisomes?
Contain enzymes which oxidise long-chain fatty acids
What is a typical diameter of a microfilament?
5nm
What is a typical diameter of a microtubule?
25nm
What is a typical diameter of a intermediate filament?
10nm
Where can cytokeratins be located?
Epithelial cells
Where can desmin be located?
Myocytes
Where can glial fibrillary acidic protein be located?
Astrocytic glial cells
Where can neurofilament protein be located?
Neurons
Where can nuclear laminin be located?
Nuclei of all cells
Where can vimentin be located?
Mesodermal cells
What is lipofuscin and where is it commonly found?
- Membrane-bound orange-brown pigment
- Common in heart/liver
What are the 3 functions of epithelia?
Protection, absorption and secretion
What are the 3 types of muscle?
Smooth, skeletal and heart
Name 4 supporting tissues
Cartilage, bone, tendons and blood
What does epithelial compromise of?
A cohesive sheet of cells, with one or more layers, resting on a basement membrane
How is epithelia categorised?
According to the shape of the cells and the number of layers of cells
What is simple epithelia?
A single layer of cells on a basement membrane
What is stratified (compound) epithelia?
Two or more layers of cells on a basement membrane
What is simple squamous epithelium?
A single layer of flattened plate-like cells on a basement membrane with parallel oval nuclei
What is endothelium?
The simple squamous epithelium which lines the inside of blood vessels
What is mesothelium?
The simple squamous epithelium which lines the outside of the lungs
What is peritoneum?
The simple squamous epithelium which lines the abdominal organs
What is simple cuboidal epithelium?
A single layer of cells with similar height and width on a basement membrane, central spherical nuclei
Name 2 places where the simple cuboidal epithelium lines
- Kidney tubules
- Small ducts
What is simple columnar epithelium?
A single layer of cells taller than they are wide, on a basement membrane. They may have cilia or microvilli
Name 3 places where the simple columnar epithelium lines
- Stomach
- Intestines
- Uterus
What are microvilli?
- Microscopic projections on luminal surface of absorptive cells
- Increase SA
Where may microvilli be found?
Intestinal brush border
What is cilia?
Microscopic motile projections on luminal surface of cells
Where may cilia be found?
Respiratory or reproductive tracts
Give 2 features of stratified epithelia
- Protective function
- Many layers of cells
Where is stratified epithelia usually found?
At sites subject to abrasive forces
What is stratified squamous non-keratinising epithelium?
- Multiple layer of cells on a basement membrane
- Mature surface layers are plate-like squames
Name 3 places which stratified squamous non-keratinising epithelium lies
- Mouth
- Oropharynx
- Vagina
What is stratified squamous keratinising epithelium?
- Multiple layer of cells on a basement membrane
- Mature surface layers are plate-like squares
- Waterproof layer of keratin
Where is stratified squamous keratinising epithelium found?
Skin
What is pseudostratified epithelium?
A single layer of cells of variable height, mimicking multiple layers on a basement membrane
Where is pseudo stratified epithelium found?
Lines the conducting airways
What is urothelium?
A specialised stratified epithelium
What is the structure of urothelium?
- Surface layer of umbrella cells
- Cells between umbrella cells appear 3-7 layers thick
Where is urothelium found?
The collecting part of the urinary tract
What is the basement membrane made of?
Several extra-cellular proteins including collagen IV and fibronectin
What is the function of the basement membrane?
Essential for the proper functioning and survival of the epithelium
What is an occluding (tight) junction?
Band-like fusions between cells that are impervious to most molecules, prevents diffusion between cells
What are desmosomes (anchoring/adherent junctions)?
- Plaques that form physical joins between cells and connect the cytoskeletons of adjacent cells
- Spread forces across several cells
What are gap junctions (aka communicating junctions)?
Electrical junctions that permit the transfer of small molecules, electrically couple adjacent cells
What is the origin of connective tissue cells?
Mainly derived from undifferentiated mesenchymal cells, but may also be from the haemopoietic stem cell line
Name the 5 cell types which are derived from mesenchymal cells
- Mast cells
- Fibroblasts
- Chondroblast
- Osteoblast
- Adipocytes
What do fibroblasts later derive into?
Fibrocytes
What do chondroblasts later derive into?
Chondrocytes
What do osteoblasts later derive into?
Osteocyte
What are the 3 constituents of connective tissues?
- Cells
- Visible fibres
- Ground substance (a hydrophilic jelly and invisible fibres)
What are the 3 types of connective tissues?
- Fibrous (loose/dense)
- Hard (cartilage/bone)
- Fatty (white/brown)
What is tropocollagen?
A triple helix of peptides
Where is tropocollagen secreted from?
Fibroblasts
Where is type I collagen found?
Skin
Where is type II collagen found?
Cartilage
Where is type III collagen found?
Liver, bone marrow, spleen (reticulin)
Where is type IV collagen found?
Basement membranes
Where is type V collagen found?
Placenta
What colour do collagen fibres stain with H&E?
Pink
Give 3 features of loose connective tissue
- Widely spaced thin collagen fibres
- Fibroblasts/fibrocytes
- Unstained ground substance
Give 4 features of dense connective tissue
- Closely spaced thick collagen fibres
- Fibroblasts/fibrocytes
- Unstained ground substance
- May be irregular or regular
Give 4 features of reticulin
- Type III collagen
- Fibrillar collagen
- Forms a supporting scaffold in many organs
- Not visible with H&E - need a silver stain
What does elastic tissue compromise of?
Fine fibres and sheets of elastin
Give 3 features of elastin
- May be branched
- Produced by fibroblasts
- Stain pink on H&E
What is the structure of white adipose (fatty) tissue?
Large cells with a single fat globule in each cell
What is the structure of brown adipose (fatty) tissue?
Cells with many globules of fat
Where is brown adipose tissue found in a newborn?
Across the shoulders and down the back
What is the importance of brown adipose tissue in a newborn?
Important in neonatal thermos-regulation
What are the 4 constituents of cartilage?
Cells, extracellular matrix, proteoglycans and extracellular fibres
Is cartilage vascular or avascular?
Avascular
Where is hyaline cartilage usually found?
In synovial joints
What is the structure of hyaline cartilage?
Chondrocytes in lacunae surrounded by a amorphous matrix. has no visible fibres
What is perichondrium?
Fibroblasts and collagen
Name 2 places where elastic cartilage can be found
- Pinna
- Epiglottis
What is the structure of elastic cartilage?
Visible elastic fibres in matrix and perichondrium
Where can fibrocartilage be found?
In the annulus fibrosus pubic symphysis
What is the structure of fibrocartilage?
Visible collagen fibres matrix and perichondrium
Where is synovium usually found?
Lines the inside of the joint capsule
What is the structure of the synovium?
- 1-4 layers of synovial cells
- Type A (phagocytes) and Type B (rich in RER)
- Variable shapes (squamous to cuboidal)
- Richly vascular
- Highly innervated
Where is visceral (smooth) muscle found?
- Arterial wall
- Wall of intestine
- Airways of lungs
Where is voluntary (skeletal) muscle found?
- Skeletal muscle
- Larynx
- Diaphragm
Where is cardiac muscle found?
- Heart
- Base of great vessels
Name 3 other contractile cells
- Pericytes
- Myo-Fibroblasts
- Myo-epithelial cells
Give 5 properties of smooth muscle?
- Involuntary muscle
- Fusiform cells
- Central nucleus
- No striations
- Non-branching
What is the general structure of arteries (inside to outside)?
- Lumen
- Intima
- Basement membrane
- Internal elastic lamina
- Media
- External elastic lamina
- Adventitia
Where are the elastic arteries found?
Near the heart e.g. aorta and pulmonary arteries
What are the features of the elastic arteries?
Media contains abundant concentric sheets of elastin
What are the features of muscular arteries?
The media compromises of layers of smooth muscle. Little elastin is in the media
Which vessels are ‘resistance vessels’?
Arterioles
What are arterioles arbitrarily described as?
As having 3 or fewer muscle layers in their media. The elastic laminae is poorly defined
What is the structure of a capillary (from inside to outside)?
Lumen, endothelium and a basement membrane
What are capillaries composed entirely of?
Thin-walled endothelial cells with no surrounding muscle or connective tissue
Which tissues tend to have fenestrated capillaries?
Kidney and liver
What is the structure of veins (from inside to outside)?
- Lumen
- Intima
- Basement membrane
- Internal elastic lamina
- Media
- Adventitia
What is the structure of venues?
Thin walled, contractile pericytes wrap around outside of endothelial cells and form a complete layer as venues get larger
What gets replaced as venues become veins?
Pericytes get replaced by smooth muscle
What is the structure of lymphatics?
- Thin walled
- Similar to capillaries and veins
- Have valves
- Don’t contain blood
- Contains eosinophilic lymph
- May contain lymphocytes
What is the structure of peripheral nerves?
- Composed of axons supported by Schwann cells
- Most are myelinated
- Myelin is produced by Schwann cells
What are the myelinated peripheral nerve components?
Endoneurium, perineurium and epineurium
Where is endoneurium present?
Between individual axons
Where is perineurium present?
Surrounds the groups of axons to form fascicles
Where is epineurium present?
Binds fascicles together to form nerve fibres
What is the structure of a small peripheral nerve fibre?
Bundle of axons interspersed with endometrium and surrounded by perineurium and epineurium
What is myelin and what is its function?
It is a spiral of apposed Schwann cell membranes. It insulates axons
How many Schwann cells are there per myelinated axon?
Multiple
How many axons are there per Schwann cells?
One
What are the gaps between myelin?
Nodes of Ranvier
What is significant about myelinated axons?
- Larger
- Transmit impulses faster than unmyelinated ones
Name 4 peripheral nerves
Motor neurones, sensory neurones, sympathetic neurones and parasympathetic neurones
What is the structure of motor neurones?
Cell bodies in grey matter of spinal cord
What is the structure of sensory neurones?
Cell bodies in dorsal root ganglion
What is the structure of sympathetic neurones?
Cell bodies in grey matter or cord and in adjacent sympathetic ganglia
What is the structure of parasympathetic neurones?
Cell bodies in brain and local ganglia
What is the pericardium?
Outermost layer of the heart
What are the two types of pericardium?
Visceral and parietal
What is the structure of the pericardium?
Layer of mesothelial cells resting on thin layer of fibrous connective tissue
What is the epicardium and where is it situated?
The underlying adipose tissue, vessels and nerves. it is between the pericardium and myocardium
What is the structure of specialised cardiac muscle?
- Striated
- Central nuclei
- Branching
- Intercalated discs
What is endomysium?
Loose fibrous connective tissue between the muscle fibres in the myocardium
What is the myocardium?
The thickest layer of the heart
Which type of myocytes are larger?
Ventricular. Atrial are smaller
What do atrial myocytes contain?
Perinuclear neuroendocrine granules (for atrial natriuretic peptide)
What is the conducting system of the heart?
- SAN
- AVN
- Bundle of His
- Purkinje fibres (subendocardial and large vacuolated muscle cells)
What is the endocardium and what is it compromised of?
- Innermost layer of the heart
- Thin layer of fibrous connective tissue
- Endothelial cells
Where are heart valves found and what are they covered by?
Covered by endothelium and attach to central fibrous body
What do heart valves consist of?
Fibrosa (dense fibrous CT), spongiosa (loose fibrous CT) and ventricularis (collagen dn elastin)
What is the structure of cardiac myocytes?
Branching cells with a single nucleus. Their myofibrils are in register, so they appear striated
What hormone do atrial myocytes secrete?
Atrial natriuretic peptide
Where can Purkinje fibres be found?
Beneath the endocardium
What is the function of Purkinje fibres?
To transmit electrical impulses
What is the structure of the Purkinje fibres?
Large specialised cardiac muscle cells with a cytoplasm rich in glycogen
Which is smaller: myocytes of the SAN or regular?
Those of the SAN
What is the difference between SAN myocytes and regular myocytes?
The myocytes of the SAN have no intercalated discs and are joined by desmosomes . They are embedded in fibrous tissue
Name two things which all cardiac myocytes have.
A nucleus and mitochondria
What cell type lines the mitral valve?
Endothelial cells
What cell type lines the inner surface of the heart, including the surface of the cardiac valves?
Vascular endothelial cells
Where are the nodules of Arantius found?
In the aortic valve cusps
What are the nodules of Arantius?
Nodules of fibroelastic tissue on the centre of each free edge of each of the valve cusps in the aortic and pulmonary valve
Where are the nodules of Arantius more prominent?
The aortic valve, due to increased pressure in that side of the circulation
What is the yellow pigment which accumulates in cardiac myocytes with increasing age?
Lipofuscin
How is lipofuscin formed?
By periodisation of membrane lipids
Where do the coronary arteries run?
In the epicardium
What is the structure of the coronary arteries?
Medium-sized muscular arteries with external elastic lamina
Where are Weibel-Palade bodies found?
The endothelial cells in the heart
What is the function of Weibel-Palade bodies?
Storage granules found in the cytoplasm which contain vo Willebrand factor and other vascular mediators
Name 4 places which lacks lymphatics
- Cartilage
- Eye
- Bone marrow
- Spinal cord
What is the structure of respiratory epithelium?
- Pseudostratified
- Ciliated epithelial cells
- Interspersed goblet cells
Where does respiratory epithelium line?
The tubular portion of the respiratory tract (Nasopharynx, bronchi, conducting airways and sinuses)
What cells are the alveoli lined by?
Pneumocytes
What are the nares lined by?
Stratified squamous keratinising epithelium
What are the vocal cords lined by?
Non-keratinising stratified squamous epithelium
What is the apex of the nasopharynx lined by?
Olfactory epithelium
What holds open the larynx and trachea?
Hyaline cartilage. Holds the airways open against negative pressure during inspiration
What bridges the gap between the free ends of the C-shaped cartilages in the trachea?
Smooth muscle (trachealis
What is present in the walls of the bronchi but not in the bronchioles?
Cartilage
Where is Reinke’s space?
In the vocal cords
What is Reinke’s space occupied by and where does it lie?
- Occupied by the loose irregular fibrous tissue
- Lies between vocal epithelium. Beneath that is the vocalis muscle
What does type II pneumocytes secrete?
Surfactant
What do goblet cells produce?
Mucus
What do Clara cells do?
Secrete lipoproteins that prevent luminal adhesion
What do type I pneumocytes do?
Form the air/blood barrier
What do alveolar macrophages do?
Act as phagocytes
What are the layers of the air-blood barrier?
- Surfactant
- Type I pneumocyte
- Basement membrane
- Vascular endothelial cell
How thick is the air-blood barrier?
600nm
Where are the pores of Kohn found?
In the alveolar walls
What is the function of the pores of Kohn?
They connect adjacent alveoli to each other. They allow for rapid even distribution of air through the lung on inhalation
What is a disadvantage of the pores of Kohn?
They allow for the passage of microbes, which may result in lobar pneumonia
What is the histological structure of the posterior third of the tongue?
Stratified squamous non-keratinising epithelium over a loose fibrous connective tissue
What does the epithelium overlie in the posterior third of the tongue?
A lymphoid infiltrate (part of Waldeyer’s ring)
Where is the circumvallate papillae?
Between the anterior 2/3 and posterior 1/3 of the tongue. It forms a V shaped line
What is the function of the filiform papillae?
To roughen the surface of the tongue, to help aid in mastication
What is the most numerous papillae on the tongue?
The filiform papillae
Where is the filiform papillae found?
The dorsal surface of the tongue
What is the colour of the cytoplasm in mucous glands?
Clear
What kind of gland is the submandibular gland?
Mixed mucous/serous
What kind of gland is the sublingual gland?
Mostly mucous
What kind of gland is the buccal gland?
Mostly mucous
What kind of gland is the lingual gland?
Mostly mucous
What are the features of oesophageal mucosa?
- Non-keratinising stratified squamous epithelium
- Lymphocytes in the submucosa
- Mucinous glands in the submucosa which have squamous-lined ducts
What epithelium lines gland ducts?
Squamous or epithelium
What is the structure of gastric antrum?
- Has long branching crypts
- Lined by mucous-secreting cells
- Lack of parietal cells
Which cells secrete intrinsic factors?
Parietal cells
What do gastric parietal cells secrete?
Hydrochloric acid and intrinsic factor
What do the surface mucous cells secrete?
A bicarbonate rich mucous
What is one role of intrinsic factor?
Helps with absorption of vitamin B12, which enters via the diet
What do chief cells secrete?
Pepsinogen, which is later cleaved to activate pepsin in the gastric lumen
What are the common presentations of the duodenum?
Broad leaf-like villi and the submucosal Brunner’s glands
What is the role of Brunner’s glands?
Secrete an alkaline mucus that helps neutralise gastric acid
What is chyme?
Digested food that leaves the stomach
What does ileum look like histologically?
- Villous appearance
- Prominent lymphoid aggregates (Peyer’s patches) in the submucosa and mucosa
Name a histological difference between the ileum and the jejunum & duodenum
The jejunum & duodenum don’t have Peyer’s patches
Name a histological difference between the ileum and the appendix & colon
The appendix and colon don’t have a villous architecture
Where does Auerbach’s plexus lie in the colon?
Muscular propria
What are the two autonomic nerve plexuses which innervate the GI tract?
Meissner’s plexus and Auerbach’s plexus
Where does Meissner’s plexus lie?
In the submucosa
Where does Auerbach’s plexus lie?
Between the layers of the muscularies propria
What is significant about the muscular propria in the colon?
It is double layered. The layers are the inner circular and outer longitudinal
What is the structure of the epithelium in the colon?
A simple columnar layer of mucus-secreting enterocytes
What is something which is featured in the small intestine, but not the colon?
A prominent brush border
Where are the epithelial stem cells of the colonic mucosa found?
At the base of the crypts of the Lieberkhun
Where is the muscular mucosa of the colon found?
Immediately below the lamina propria
What arteries supply the colon?
The superior mesenteric artery and inferior mesenteric artery
Where is vitamin B12 absorbed?
In the terminal ileum
What is the structure of a classic lobule of the liver?
- Roughly hexagonal
- A portal vein, hepatic artery and bile duct at each corner
- Central vein in the middle of the hexagon
Where is bile synthesised?
Hepatocytes
What are the phagocytes of the liver?
Kuppfer cells
What are the antigen presenting cells of the liver?
Ito cells
Where are Ito cells found?
Space of Disse
Where is angiotensinogen synthesised?
The liver
Where does haematopiesis take place in the foetus?
Hepatic sinusoids
What is the structure of hepatocytes?
Large polygonal epithelial cells that are arranged in plates compromising thin cords of hepatocytes, supported by a meshwork of type 3 collagen (reticulin). They have a microvillous brush border and abundant mitochondria
What is the function of the SER in hepatocytes?
Inactivates drugs and toxins
What is the function of the RER in hepatocytes?
A role of synthesis of plasma proteins
What is a function of the Ito cells?
Store fat in the liver
Where can Kuppfer cells be found?
Lie in the sinusoids of the liver
What cells are Kuppfer cells derived from?
Monocytes
What will happen to Kuppfer cells in a patient with haemochromatosis?
The cells will accumulate the pigment haemosiderin, which contains iron
What can hepatocytes store?
Fat soluble vitamins
What can the gall bladder absorb?
Water
What is the structure of the gallbladder epithelium?
Columnar, with a prominent microvillous brush border
Why do the cells of the gall bladder absorb water?
To concentrate the bile that was secreted by hepatocytes
Where are acinar cell found?
Exocrine pancreas
What is the function of acinar cells?
Secrete a wide variety of enzymes (all of which are in precursor form)
Where is secretin secreted from?
The endocrine cells of the GI tract
Where is albumin made?
The hepatocytes
Where are centriacinar cells found?
Exocrine pancreas
What is the function of centriacinar cells?
- First part of the ductal system of the pancreas
- Secrete a bicarbonate-rich alkaline solution when stimulated by secretin
- Secretes mucin
What is the function of cholecystokinin?
Causes acinar cells to release digestive enzymes by exocytosis
Where is insulin and pancreatic polypeptide secreted from?
Islets of Langerhans
Which structure appears to most prevalent in the renal cortex?
The proximal convoluted tubule
Which structure lines the outside of the basement membrane of the glomerular capillaries?
Podocytes
Which arteries directly gives rise to the afferent arterioles in the kidney?
Interlobular arteries
What is the name given to the epithelium which lines the renal pelvis?
Urothelium
Where can pseudo stratified columnar ciliated epithelium be found?
Trachea of the lungs
What epithelium lines the ducts and convoluted tubules of the kidney?
Simple cuboidal
Where is renin secreted from?
The macula densa of the kidneys
Where is aldosterone made?
In the adrenal gland in the adrenal cortex
Where is vasopressin made?
In the hypothalamus but secreted by the posterior pituitary
What is the juxtaglomerular apparatus?
Macula densa + afferent arteriole
Where in the kidney is very responsive to aldosterone?
The collecting ducts
What are Lacis cells?
Lightly staining pericytes in the kidney
What does the ureter lack?
Muscular mucosa
What is the most easily discerned at the bladder neck?
Muscular propria
What is the structure of the male urethra?
A membranous urethra lined by urothelium
Where does the external sphincter lie in the male urethra?
Surrounds the membranous urethra
What is the outermost layer of the epidermis?
Stratum corneum
What is the layer of the epidermis which contains the melanocytes?
Stratum basale
What is the layer of the epidermis which contains visible desmosomes?
Stratum spinosum
Where is keratin synthesised?
In the stratum granulosum of the epidermis
What is the function of melanocytes?
To synthesise melanin from tyrosine
What is a hair follicle?
A down-growth of the epidermis into the dermis
What is a hair bulb?
A downward extension of the epidermis into the dermis
What is a hair papilla?
A specialised part of the dermis that is richly innervated and richly vascular
Where are apocrine sweat glands usually found and what cytoplasm type do they have?
- Found in skin around anus/genitals
- Eosinophilic cytoplasm
Which glands open directly onto the surface of the labia?
Sebaceous glands
What do Pacinian Corpuscles do?
Sense changes in pressure. They have a part which is compromised of Schwann cells
What do B cells do?
Become plasma cells and secrete antibodies
What do T cells do?
Involved in cell mediated immunity
What do T helper cells do?
Helps B cells and activates macrophages
What do T cytotoxic cells do?
Kill previously marked target cells
What do T suppressor cells do?
Suppress TH cells and hence suppress the immune response
What do natural killer cells do?
Mainly kill virus infected cells
What do monocytes do?
- Immature cells
- Circulate briefly in the blood
- Readily differentiate into other cells
Where do monocytes differentiate into tissue macrophages?
Everywhere
Where do monocytes differentiate into Kupffer cells?
Liver
Where do monocytes differentiate into osteoclasts?
Bone
Where do monocytes differentiate into antigen presenting cells?
Everywhere
Where do monocytes differentiate into alveolar macrophages?
Lung
What are the functions of platelets?
Responsible for clotting blood, notably when the endothelium lining all blood vessels is breached
What is the structure of respiratory epithelium?
Pseudostratified, ciliated epithelial cells with interspersed goblet cells
Where does respiratory epithelium line?
The tubular portion of the respiratory system
Name 4 functions of the nose
Filtration, humidification, warming and olfaction
What is the cell structure of the nose?
- Both keratinising and non-keratinising squamous epithelium
- Respiratory epithelium
- Richly vascular lamina propria containign seromucinous glands
How does olfaction happen in the nose?
Olfactory receptor cells and bipolar neurones in the pseudo stratified columnar epithelium
Name 4 functions of the nasopharynx
Gas transport, humidification, warming and olfaction
What cell type is the nasopharynx lined by?
Respiratory epithelium
Give 3 functions of the nasal sinuses
- Lower the weight of the skull
- Add resonance to the voice
- Humidify and warm inspired air
What are the nasal sinuses lined by?
Respiratory epithelium
What is the function of the larynx?
Voice production
What is the structure of the larynx?
- Cartilaginous box
- Respiratory epithelium
- Loose fibrocollagenous storm with seromucinous glands
- Lymphatics and blood vessels common
What is the function of the vocal cords?
Voice production
What is the structure of the vocal cords?
Stratified squamous epithelium overlying loose irregular fibrous tissue (Reinke’s space), almost no lymphatics
What is the function of the trachea?
Conducts air to and from the lungs
What is the structure of the trachea?
- Respiratory epithelium
- Seromucinous glands in submucosa
- Trachealis muscle posteriorly
- C-shaped cartilaginous rings
What are the functions of Clara cells?
- Most numerous in terminal bronchioles
- Oxidise inhaled toxins
- Antiprotease function
- Surfactant production/elimination
- Stem cell
What are the functions of respiratory bronchioles?
- First part of distal respiratory tract
- Gas exchange as well as transport
- Link terminal bronchioles and alveolar ducts
What is the structure of respiratory bronchioles?
- Cuboidal ciliated epithelium
- Spirally-arranged smooth muscle
- No cartilage
What is the function of the alveoli?
Gas exchange
What is the function of Type I pneumocytes?
Allow for gas exchange
What is the function of Type II pnuemocytes?
Produce surfactant
What is the function of alveolar macrophages?
Phagocytose particulates including dusts and bacteria
What is the order of the blood-air barrier of the alveoli?
Type I pneumocytes, fused basement membrane of pneumocyte and capillary, vascular endothelial cell
What is the interstitium in the lung?
Where endothelial cells aren’t in direct contact with pneumocytes
What is the visceral pleura?
Flat mesothelial cells in the lungs
What type of cells are Sertoli cells?
Phagocytes
Where is testosterone secreted from?
Leydig cells
Which cells contain Reinke’s crystalloids?
Leydig cells
How much does the normal human test weigh?
15-19g
Where do the rete testes lie?
Between the straight tubule and epididymis
Where is the site of acid phosphatase storage?
The prostate
Where does sperm mature?
The epididymis
Give 2 features of the corpus spongiosum
- Highly vascular
- Urothelium lining duct
Where is the spiral mitochondria kept in the spermatozoa?
The body/midpiece
Where is there abundant lipofuscin in males?
The seminal vesicles
What is the function of PSA?
Liquidises semen after ejaculation
What is the basic function of FSH?
Causes proliferation of ovarian follicles
How many primordial follicles are present at birth?
400,000
What is the usual cite of fertilisation?
The Fallopian tube
What function is a prominent brush border usually linked to?
Absorption
Name the two parts of the body with ciliated epithelium
Fallopian tube and respiratory tract
Which part of the female reproductive tract is hormonally sensitive?
All of it
What does the endocervix do to act as barrier against sperm?
Secretes mucus to act as a barrier
What is proliferative endometrium characterised by?
The presence of stroll mitotic figures
What is significant about the cervical transformation zone?
It is a prominent site for cervical cancer to form
Give 2 features of secretory endometrium
- Prominent spiral arteries
- Subnuclear glycogen vacuoles
Give 3 features of early secretory phase of the endometrium
- Growth occurring in the glands
- Pale vacuoles (subnuclear)
- Lack of luminal secretions
What epithelium does the labia majora have?
Stratified squamous keratinising epithelium with hairs
What is the structure of the gut from inside to outside?
- Lumen
- Epithelium
- Basement membrane
- Lamina propria
- Muscularis mucosae
- Submucosa
- Inner circular layer
- Outer longitudinal layer
- Adventitia/serosa
- Muscularis propria
What is the structure of the stomach from inside to outside?
- Lumen
- Epithelium
- Basement membrane
- Lamina propria
- Muscularis mucosae
- Submucosa
- Innermost oblique layer
- Middle circular layer
- Outermost longitudinal layer
- Adventitia/serosa
- Muscularis propria
What is the purpose of the oral cavity?
Receives food, chews food and starts digestion
What kind of cancer is oral cancer?
Squamous cancer
What are the 3 salivary glands?
- Parotid gland
- Submandibular gland
- Sublingual gland
What is the purpose of salivary glands?
Produce saliva and enzymes
What is Sjorgen’s syndrome?
No saliva production
What is the purpose of the oesophagus?
Swallow food
What is the cellular structure of the oesophagus?
- Squamous epithelium
- Has sub mucous glands
What is the purpose of the stomach?
Digests food
What do parietal cells of the stomach do?
Secrete HCl
Name 2 substances what chief cells secrete
Pepsinogen and lipase
Give 4 purposes of the intestines
- Digest food
- Absorb food
- Absorb water
- Resist bugs
What is the function of the interstitial cells of Cajal?
‘Pacemaker’ which creates the potential which leads to the contraction of smooth muscle
Give the basic anatomy of the GI tract in order
Stomach, duodenum, jejunum, ileum, large intestine (colon)
What is the purpose of the duodenum?
- Digests food
- Absorbs food
- Resist bugs
What is the purpose of the jejunum and ileum?
Digests food, absorbs food and resists bugs
What is the purpose of the appendix?
The ‘safe house’
What is the anatomy of the large colon?
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anus
What is the purpose of the colon?
- Absorbs food
- Absorbs water
- Resists bugs
What do the portal tracts in the liver contain?
Portal veins, arteries and bile ducts
How are hepatocytes arranged in the liver?
Arranged into cords with intervening sinusoids and central veins
What is the conventional design of the cells in the liver?
- Divided into classic lobules
- Bile duct, portal vein and hepatic artery at each ‘corner’ of the hexagon with a central vein in the middle
What is the drainage of the classic lobule in the liver?
An area drained by one central hepatic lobule
What is the acinus structure of hepatocytes in the liver based around?
Blood supply rather than drainage
What is the structure of the acinus in the liver?
Links the central vein in two different hexagons by 2 sets of bile ducts, portal veins and hepatic arteries
Why is there some variation in the size of different hepatocytes?
Some are more richly oxygenated
Give 10 features of hepatocytes
- Principle functional cells of the liver
- Polyhedral epithelial cells
- Abundant mitochondria
- Large central spherical nuclei
- Prominent nucleoli
- Active Golgi
- Prominent ER
- Lots of mitochondria
- Numerous perioxisomes
- May be binucleate
What are the 3 important surfaces of the liver and what are their proportions?
Sinusoidal (70%), canalicular (15%) and intercellular (15%)
What is the function of the sinusoidal surface in the liver?
Permits exchange of material with blood (Space of Disse)
What is the function of the canalicular surface in the liver?
Permits the excretion of bile
Give 4 features of sinusoids
- Highly specialised blood vessels
- Thin discontinuous fenestrated epithelium
- No basement membrane
- Contains scattered Kupffer cells
What is the structure of the intrahepatic biliary tree and what is the change in epithelium?
- Goes from simple cuboidal to columnar epithelium
- Canaliculi to Bile ductules to Trabecular ducts to Bile ducts
Give 2 functions of the gallbladder
- Concentrates and stores bile
- Expels bile via common bile duct into duodenum
What is the structure of the specialised mucosa of the gallbladder?
- Simple columnar epithelium
- Microvilli
- Thrown into folds
- Adapted for water and salt absorption
- Connective tissue (lamina propria)
What is the function of the exocrine pancreas?
To synthesise and secrete enzymes and a bicarbonate-rich fluid into the duodenum
What is the structure of the exocrine pancreas?
- Poorly defined fibrous capsule with septum dividing gland into lobules
- Epithelial cells arranged into acini
Give the structure of acinar cells
- Epithelial
- Pyramidal shape
- Basally rich in RER
- Apically, has zymogen granules (enzyme precursors)
Name the 4 ducts of the exocrine pancreas
- Centroacinar cells
- Intercalated ducts
- Interlobular ducts
- Main pancreatic duct
How can the nephron’s loop of Henle be further divided?
Into a thick and thin limb
Give 7 features of the glomerulus of the nephron
- Tuft of convoluted fenestrated capillaries
- Glomerular basement membrane
- Lined by podocytes
- Supported by mesangial cells
- Encased in Bowman’s capsule
- Has capillary epithelial cells
- Mesenglial cells lie between capillaries
What is the juxtaglomerular apparatus compromised of?
Afferent arteriole and distal convoluted tubule
What does the afferent arteriole contribute?
Granular cells
What is the function of renin?
Secreted in response to low blood pressure, to increase blood pressure
What is the macula densa?
A patch of closely packed endothelial cells along the distal convoluted tubule
What is the function of the macula densa?
Senses NaCl concentration and regulates tubuloglomerular feedback
What is the structure of the proximal convoluted tubule?
- Cuboidal epithelium
- Round central/basal nuclei
- Brush border of microvilli at apical end
- Many mitochondria so appear eosinophilic
What is the function of the proximal convoluted tubule?
Reabsorption of NaCl, proteins, polypeptides, amino acids and glucose
What is the cell type in the thin segment of the loop of Henle?
Simple squamous
What is the cell type in the thick segment of the loop of Henle?
Low cuboidal
What is the blood supply to the loop of Henle?
The rich vasa recta
What is the epithelium in the distal convoluted tubule?
Low cuboidal epithelium
Give 2 significances in structure of the distal convoluted tubule
- Scanty microvilli
- Numerous mitochondria
What are the 2 functions of the distal convoluted tubule?
- Regulates acid-base by secreting hydrogen ions and absorbing bicarbonate via cellular carbonic anhydrase
- Regulates Na level by exchanging Na for K
What is the epithelium in the collecting duct?
Cuboidal epithelium
What is the function of principle cells in the collecting duct?
Respond to aldosterone and ADH
What is the function of intercalated cells in the collecting duct?
Exchange hydrogen ions for bicarbonate ions
Name 5 arteries which supply the kidneys
- Abdominal aorta
- Renal artery (at L1)
- Interlobular artery
- Interlobar artery
- Arcuate artery
Name 3 veins which drain the kidneys
- Vasa recta
- Renal veins
- Inferior vena cava
What endothelium does the renal pelvis have?
Urothelium
What is the function of the renal pelvis?
Transmits filtrate from nephron to ureter
What is urothelium?
- Specialised epithelium found in the collection/drainage parts of the urinary tract
- Complex stratified epithelium
- Layer of umbrella cells overlies a pseudostratified layer of polygonal cells
What is the epithelium in the ureters?
Transitional epithelium
What is the structure of the ureters?
- Spiral muscular tube (inner - longitudinal & outer - circular)
- No serosa
- Loose adventitia
What is the epithelium in the bladder?
Urothelium
What are the cell layers in the bladder?
- Urothelium
- Lamina propria
- Muscularis mucosa
- Submucosa
- Muscularis propria
- Subserosa and serosa
How is reflux into the ureter from the bladder prevented?
By a functional valve
How long is the female urethra?
4-5cm
What is the structure of the female urethra?
- Proximally transitional epithelium
- Distally squamous epithelium
- Paraurethral and periurethral glands open into the urethra
How long is the male urethra?
20cm
What is the structure of the male urethra?
- Prostatic urethra
- Membranous urethra lined by urothelium
- Penile urethra pseudostratified epithelia proximally
- Stratified squamous epithelium distally
Which parts of the body have urothelium?
Renal pelvis, ureter, bladder and urethra
Name the glands which are present in the epidermis
Eccrine, apocrine and sebaceous glands
What is the structure of the basement membrane in the epidermis?
- Not usually visible with H&E
- Made of type IV collagen
What is the structure of the stratum basale in the epidermis?
- Sits on the basement membrane
- Basal epithelial cells (stem cells)
- Melanocytes
What are the function of melanocytes in the stratum basale of the epidermis?
Synthesise melanin and transfer it to surrounding keratinocytes in melansomes in response to MSH and ACTH stimulation
What is the function of melanin?
Absorbs UV light, protecting us from non-ionising radiation damage
What other two cell types are present in the stratum spinosum?
Langerhans cells and Merkel cells
What is the structure of stratum spinosum cells?
- Plump polygonal keratinocytes
- Prominent intercellular adhesions
What are the functions of the Langerhans cells in the stratum spinsoum?
For antigen recognition
What are the functions of the Merkel cells in the stratum spinsoum?
For sensory functions
What is the structure of the stratum granulosum in the skin?
- Flattened squames
- Eosinophilic cytoplasm
- Haematoxophilic keratosis-hyaline granules
What’s the structure of stratum corneum in the skin?
- Acellular
- Plates of keratin
- Prominent in certain sites
What is epidermal adnexae?
Downgrowths of the epidermis into the dermis
Give 4 examples of epidermal adnexae
- Hair follicles
- Sebaceous glands
- Eccrine sweat glands
- Apocrine sweat glands
What is the function of sebaceous glands in the skin?
- Accompany hair follicles
- Produce sebaceous secretions which lubricate and waterproof hairs
What kind of secretion do the sebaceous glands do?
Holocrine secretion
What is the function of apocrine glands in the skin?
- Accompany hair follicles
- Axillae and groins ceruminous glands in the ear
What is the function of eccrine glands?
Give a thin watery secretion
What is the space in the derma-epidermal junction?
The papillary dermis
What is the general structure of the dermis?
- Irregular loose connective tissue
- Fibroblasts
- Collagen
- GAG matrix
- Blood vessels + lymphatics
- Nerves
- Sensory cells
- Scattered inflammatory cells
What are the sensory structures of the dermis?
- Meissner’s corpuscle
- Pacinian corpuscle
What is the structure of Meissner’s corpuscle?
Encapsulated unmyelinated nerve endings, dermal papillae, especially in hairless skin
What is the function of Meissner’s corpuscle?
For fine touch
What is the structure of Pacinian corpuscle?
Large encapsulated sensory receptors, central non-myelinated nerve and surrounding lamellae
What is the function of Pacinian corpuscle?
For vibration and tickle
What is the structure of the subcutis?
Adipose tissue and fibrovascular septa
What are the functions of the subcutis?
- Insulation
- Shock-absorber
- Food store
What is the structure of the breast tissue?
Myoepithelial system of ducts and lobules set in fibroadipose tissue, ducts all empty at the nipple
When is breast tissue present from?
Birth
What is the structure of terminal duct lobular units in the breast?
Lobules are arranged around a terminal duct and are set in loose fibrous connective tissue
What are the ducts and lobules of the breast lined by?
- Two layers of cells
- Outer myoepithelial and inner columnar epithelial
What is the process regarding lactation?
Ducts and an inner layer of secretory cells which become vacuolated
What are the three histological layers of the skin?
Epidermis, dermis and subcutis. The epidermis and dermis can be further subdivided
What two features of skin are downgrowths of the epidermis?
- Sweat glands
- Hair follicles
What are the testis and how much do they weigh?
- Paired organ in the scrotum
- Average weight 15-19g
What are the 4 layers of the testis?
- Capsule
- Tunica vaginalis
- Tunica albuginea
- Tunica vasculosa
What is the cellular structure of the tunica vaginalis?
Flattened layer of mesothelial cells
What is the cellular structure of the tunica vasculosa?
Loose connective tissue containing blood vessels and lymphatics
How is testicular parenchyma divided?
Into lobules by septa originating from the capsule
How many lobules are there in the testicular parenchyma?
Around 250
What do the lobules of the testicular parenchyma contain?
1-4 seminiferous tubules
What do seminiferous tubules contain?
Germ cells in varying stages of maturation and Sertoli cells
What do Type A spermatogonia look like?
Darkly stained stem cells and pale stained cells
What do Type B spermatogonia look like?
Differentiating progenitor cells which have spherical nuclei with densely stained masses of chromatin
What is the pattern of development for spermatogonia?
Spermatogonia - primary spermatocyte - secondary spermatocyte - spermatid - spermatozoon
What is the cellular structure of Sertoli cells?
Columnar cells on the basement membrane of the tubules
What is the function of Sertoli cells?
- Send cytoplasmic projections around the germ cells
- Supportive, phagocytic and secretory functions
What is the structure of the nuclei of the Sertoli cells?
Irregularly shaped, folded and have a prominent nucleolus
What is present in the head of spermatozoa?
Acrosomal cap and nucleus
What is present in the midpiece of spermatozoa?
Spiral mitochondria
What is present in the tail of spermatozoa?
Neck (centrioles), axoneme and plasma membrane
Where are Leydig cells found?
Singly and in clusters in the interstitial between tubules
Name two features of Leydig cells
- Abundant cytoplasm containing lipid
- Has Reinke’s crystalloids
What is the function of Leydig cells?
Produce testosterone
What is the rete testes?
An network of tubules at the hilium of the testis
What is the function of the rete testis?
Receive luminal contents from seminiferous tubules. Acts as a mixing chamber
What is the cellular structure of the rete testis?
Lined by simple squamous or low columnar epithelium on a relatively thick basement membrane
What is the structure of the efferent ducts of the male reproductive system?
12-15 convoluted tubules which empty into epididymis
What is the cellular structure of the efferent ducts?
Lined by ciliated and non-ciliated simple columnar epithelium with interspersed cuboidal cels (basal cells) giving a pseudostratified appearance
What is the structure of the epididymis?
A tubular structure 4-5cm long containing a highly convoluted epididymal duct
What is the cellular structure of the epididymis?
- Lined by tall columnar cells with long typical cilia
- Epithelium supported by a thick basement membrane surrounding which is a well-defined muscular coat
What is the structure of the vas deferens?
- 30-40 cm tubular structure arising from the caudal portion of the epididymis
- Distal part enlarged to form the ampulla which joins the excretory duct of the seminal vesicle to form the ejaculatory duct
What is the cellular structure of the vas deferens?
- Lined by pseudostratified columnar epithelium comprising columnar and basal cells
- Has thick muscular wall of 3 layers
What is the prostate?
- A pear shaped glandular organ
- Weighs up to 20g in young adult
Where does the prostate surround?
The bladder neck and prostatic urethra
What are the lobes of the prostate?
Anterior, middle, posterior and two lateral lobes
What are the gland regions of the prostate?
Peripheral, central, transitional and peri-urethral
What is the prostate covered by?
An ill-defined fibro-connective tissue capsule
Name the two main components of the prostate
Glandular and non-glandular components
What are the ducts of the prostate?
Large primary and small secondary
What are the acini of the prostate?
30-50 tubuloalveolar glands with convoluted edges
What are the acini of the pancreas lined by?
Secretory cells, basal cells and neuroendocrine cells
What do the secretory cells located on the luminal side of the prostate do?
Secrete PSA and PAP into the seminal fluid
What is the structure of the stroma of the prostate?
- Smooth muscle
- Fibroelastic fibres
- Blood vessels
- Nerves
What happens the the stroma and glands of the prostate with age?
Hyperplasia (enlargement)
What are the seminal vesicles?
Paired highly coiled tubular structure which are posterolateral to the bladder
Where does the duct of the seminal vesicle empty?
Into the ejaculatory duct
What are the seminal vesicles lined by?
Tall non-ciliated columnar epithelium
Name 2 features of the seminal vesicles
- Has vacuoles and lipofuscin
- Mucosa is folded
What is the broad structure of the seminal vesicles?
Has 2 layers of smooth muscle and an adventitia
What is the general structure of the penis?
- Erectile tissue arranged into 3 components
- Left and right corpora cavernous on the dorsal side
- Corpus spongiosum on the inferior side (surrounds urethra)
What does the erectile tissue compromise of?
- Irregular vascular spaces separated by fibroelastic tissue and smooth muscle
- Rich nerve supply
What do the testis contain?
Seminiferous tubules that produce spermatozoa
What 3 structure produce the bulk of the seminal fluid?
Prostate, seminal vesicles and Cowper’s glands
What is the ovary?
A paired organ lying on either side of the uterus close to the lateral pelvis wall
What are the three attachments of the ovary?
- The mesovary by the broad ligament
- The uterus by the utero-ovarian ligament
- The pelvic wall by the suspensory ligament
What joins the mesovary and the ovary?
The broad ligament
What joins the uterus and the ovary?
The utero-ovarian ligament
What joins the pelvic wall and the ovary?
The suspensory ligament
What is the histological structure of the ovary?
- Covered by a single layer of modified mesothelium
- A poorly defined connective tissue layer (tunica albugnia)
- Stroma is divided into cortex and medulla with indistinct boundaries
What is the structure of the ovarian cortex (top portion)?
Spindle stroma cells arranged in whorls/storiform pattern, ovarian follicles, some leutinised cells
What is the structure of the ovarian medulla (bottom portion)?
Loose fibroelastic tissue with blood vessels, lymphatics and nerves
What is the rete ovarii?
An analogue of the rete testis - present at the hilium
Where are primordial follicles found?
The periphery of the ovarian cortex
Give 2 features of primordial follicles
- Contains primary oocyte in a resting state
- Surrounded by a single layer of epithelial cells (granulosa cells)
What is the mechanism of development into primary follicles from primordial follicles?
- Cyclic FSH secretion from anterior pituitary stimulates follicular development
- Follicular epithelial cells proliferate (granulosa cells)
- Oocyte enlarges
- Stromal cells become organised into connective tissue sheath
- Zona pellucida forms directly around oocyte
What is the mechanism of development into secondary follicles from primary follicles?
- Formation of antrum (space filled with follicular fluid)
- CT differentiate into inner theca interna and outer theca externa (Cumulus oophorus)
What is the structure of mature (Graafian) follicles?
- Ovum surrounded by a thick Zona pellucida
- A layer of granulosa cells surround the oocyte (corona radiata)
- Basal lamina, theca interna and theca externa
What is the process of the conversion from a follicle to a corpus luteum?
- Luteinisation of granulosa and theca cells occurs (they become polygonal, larger in size, have abundant cytoplasm containing lipid)
- Secrete progesterone and oestrogen
What is the process of regression of a corpus luteum if fertilisation doesn’t take place?
- Starts 8-9 days after ovulation
- Granulosa cells decrease in size and develop pyknotic nuclei
- Accumulate abnormal lipid, cells undergo dissolution and are phagocytosed
What forms after the corpus luteum degenerates?
The corpus albicans
What is the structure of the corpus albicans?
Mainly composed of dense collagen fibres, it is an ovarian scar
Give two functions of the Fallopian tube
- Transports ovum to the uterus
- Fertilisation occurs here
What are the four segements of the Fallopian tube?
Intramural, isthmus, ampulla and infundibulum
Where is the intramural found?
Inside the uterine wall
Give two features of the infundibulum
- Trumpet-shaped opening to peritoneum
- Has fimbriae
How thick is the isthmus?
2-3cm (it is thick walled)
What is significant about the ampulla?
It is the expanded area of the Fallopian tubes
What is significant about the mucosa of the Fallopian tube?
Thrown into branching folds
What are the two cell types of the Fallopian tubes?
Secretory and ciliated
What are the two layers of the muscularis of the Fallopian tube?
Inner circular and outer longitudinal
What is serosa?
Connective tissue covered by mesothelium
What are the three layers of the uterus?
Endometrium, myometrium and serosa
What are the layers of the endometrium?
- Deep basal layer (stratum basalis)
- Superficial functional layer (further divided into stratum compactum (towards surface) and stratum spongiosum)
What happens in the proliferative phase of endometrium?
- Oestrogen stimulation
- Straightedges proliferating glands with mitotic activity
- No luminal secretions
- Stromal cells are spindled and compact and show mitotic activity
What happens in the secretory phase of the endometrium?
- Progesterone stimulation
- Early (sub-nuclear glycogen vacuoles)
- Mid (vacuoles above and below the nucleus and layer intraluminal secretions, glands more rounded, stroma-oedema)
- Late (elongated and saw-toothed glands with more intraluminal secretions, stroma - spiral arterioles, decimal change)
What happens in the menstrual phase of the endometrium?
- Progesterone stimulation withdraws
- Stromal haemorrhage and granulocytes
- Stromal and glandualr fragmentation
What is the structure of the myometrium?
Thick muscular wall with 3 ill-defined layers of smooth muscle: inner longitudinal, middle circular and outer longitudinal
What is the structure of the endocervix?
Loose fibromuscular stroma lined by simple columnar ciliated epithelium, thrown into crypts
What is the structure of ectocervix?
Dense smooth muscle stroma lined by non-keratinising stratified squamous epithelium
What is the structure of the mucosa of the vagina?
Lined by non-keratinising stratified squamous epithelium..
What is the structure of the stroma of the vagina?
Elastic fibres and a rich vascular network
What is the structure of the muscular wall of the vagina?
Smooth muscle cells, inner circular and outer longitudinal structure
What is the structure of the adventitia of the vagina?
Loose connective tissue
What is the histology of the labia majora?
Lined by keratinising stratified squamous epithelium and has skin adnexae
What is the histology of the labia minora?
Mostly non-keratinising stratified squamous epithelium
What is a Bartholin’s gland?
Tubuloalveolar glands. Acini lined by mucus-secreting epithelium
What are minor vestibular glands?
Simple tubular glands lined by mucus-secreting epithelium
What are Skein’s glands (periurethral glands)?
Analogous to prostate, lined by pseudostratified columnar epithelium
What is the histology of the hymen?
Lined by non-keratinising squamous epithelium
What is the structure of the clitoris?
Erectile tissue rich in blood vessels and nerves
Give 4 common features of the endocrine system
- Glandular epithelium
- Richly vascularised
- Secrete a variety of hormones
- Controlled by positive and negative feedback loops
What is the function of the pituitary?
Coordinates the endocrine organs through feedback loops
What are the two functional components of the pituitary?
Posterior and anterior
What is the structure of the posterior pituitary?
- Downwards extension of hypothalamus
- Neural tissue (axons/glial cells)
What does the posterior pituitary store/secrete?
Oxytocin and vasopressin (ADH)
What is the structure of the anterior pituitary?
- Nested epithelial pituicytes
- Richly vascular fibrous stroma
- Several different types of pituicytes
Name 6 hormones which are produced in the anterior pituitary
- Growth hormones
- Prolactin
- ACTH
- FSH
- LH
- Thyroid stimulating hormone
What hormone is produced by somatotrophs?
Growth hormone in the anterior pituitary
What hormone is produced by lactotrophs?
Prolactin in the anterior pituitary
What hormone is produced by corticotrophs?
ACTH in the anterior pituitary
What hormones is produced by the gonadotrophs?
FSH and LH in the anterior pituitary
What hormone is produced by thyrotrophs?
Thyroid stimulating hormone in the pituitary
What is the function and structure of somatotrophs?
- Diffuse cytoplasmic growth hormones
- Lateral wings of anterior pituitary
- Present throughout gland
What is the function and structure of lactotrophs?
- Polygonal cells
- Cytoplasmic processes wrap around other cells
- Variable prolactin staining
What is the structure of thyrotrophs?
- Angular chromophobes
- Elongated processes
- Variable TSH staining
What is the structure of gonadotrophs?
- Scattered round/oval cells
What is the function and structure of corticotrophs?
- Round basophilic cells
- Median of gland
- Large cytoplasmic vacuoles
What is the function and structure of supporting cells in the anterior pituitary?
- Sustenacular cells
- Surround the normal follicles
What is the structure of the pineal gland?
Pinealocytes in rosettes
Where is melatonin secreted from?
Pineal gland
Where is thyroxine produced?
Thyroid gland
Where is calcitonin produced?
Thyroid gland
What is the structure of the thyroid gland?
- A combination of follicular cells and colloid
- Richly vascular
How many parathyroid glands are there?
4
Where are the parathyroid glands located?
Variably in the neck
What do the parathyroid glands do?
Produce parathyroid hormone
What are the 3 cell types in the parathyroids?
Chief cells, oxyphils and adipocytes
What is the structure of the chief cells of the parathyroid?
- Polygonal cells
- Scant cytoplasm
- No calcium oxalate crystals
- Strong immunoreactivity for PTH
What is the function of the chief cells of the parathyroid?
- Secretes PTH
- Raises serum calcium ions
What is the structure of the oxyphil cells of the parathyroid?
- Large polygonal cells
- Increase with age
- Abundant eosinophilic cytoplasm
What is the structure of the Islets of Langerhans?
- Balls of cells
- Thin fibrous capsule
- Mostly in pancreatic tail
What are the 4 components of the Islets of Langerhans?
Beta cells, alpha cells, delta cells and PP cells
What do beta cells of the pancreas produce?
Insulin
What do alpha cells of the pancreas produce?
Glucagon
What do the delta cells of the pancreas produce?
Somatostatin
What do the PP cells of the pancreas produce?
Pancreatic polypeptide
What are the three layers of the adrenal cortex?
Zona glomerulosa, zona fasciculata and zona reticularis
What is released from the zona glomerulosa?
Mineralcorticosteroids (aldosterone)
What is released from the zona fasciculata?
Glucocorticosteroids (cortisol)
What is released from the zona reticularis?
Androgenic steroids
What is the structure of the zona glomerulosa?
Thin & incomplete, small cells, vacuolated cytoplasm
What is the structure of the zona fasiculata?
Most prominent layer, large polygonal cells, almost clear cytoplasm
What is the structure of the zona reticularis?
Innermost cortical layer, androgenic steroids, anatomising columns of small polygonal cells
What is secreted from the adrenal medulla?
Adrenaline and noradrenaline
What is the structure of the adrenal medulla?
Centre of adrenal gland, chromaffin cells, large and polyhedral
Name two features of the endocrine system
- All epithelial (except posterior pituitary)
- All have a rich blood supply
Name 3 places where visceral (smooth muscle) can be found
Arterial wall, wall of intestine and airways of lungs
Name 3 places where voluntary (skeletal) muscle can be found
Skeletal muscles, larynx, diaphragm
Name 2 places where cardiac muscle can be found
Heart & base of great vessels
Name 3 contractile cells
Pericytes, myo-fibroblasts, myo-epithelial cells
What is the structure of myoblasts in skeletal muscle?
Fused to form multi-celled syncytium
How are myofibrils formed?
By sarcomeres joined end to end
How are fascicles formed?
By the clumping of muscle fibres
Name 3 structures which are held together by connective tissue
Endomycium, perimycium and epimycium
What is significant about the cytoplasm of skeletal muscle?
It is rich in glycogen
Is skeletal muscle voluntary or non-voluntary?
Voluntary
Give 5 histological features of skeletal muscle
- Elongated fibres
- Striated cytoplasm
- Multinucleate
- Nuclei at edges
- Non-branching
Why is striated muscle striated?
Due to myofibrils being in register
What are the different types of muscle fibre?
Type 1 and 2
What is significant about type 1 muscle fibre?
Rich in fibrillar ATPase and is slow twitch
What is significant about type 2 muscle fibre?
Rich in fibrillar ATPase, fast twitch. Stains paler
What is the structure of muscle spindles?
- Intrafusal muscle fibres wrapped around by gamma efferent nerve fibres
- Fibrocollagenous capsule
What is the function of muscle fibres?
Detect stretch and tension
What is the function of Sharpey’s fibres?
- Connect muscle to bone (and penetrate bone)
- Attach muscle to bone over a wide area
What is the structure of Sharpey’s fibres?
Bundles of collagen linking epimysium to periosteum
What is the function of tendons?
- Connect muscle to bone
- Attach muscle to bone over a small area
What is the structure of tendons?
Parallel bundles of collagen with intervening fibroblasts
What is a specialised form of connective tissue?
Skeletal muscles
Name 4 cells of the bone
- Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
What forms the extracellular matrix of the bone?
Collagen and calcium hydroxyapatite
Which cells of the bone are derived from embryonic mesenchyme?
Osteoprogenitor cells
Where is osteoid secreted from?
Unmineralised bone
Which bone cells become trapped in their own matrix?
Osteocytes
Which cells of the bone connect to surrounding cells via canaliculi?
Osteoblasts and osteocytes
Which cells of the bone are derived from monocytes?
Osteoclasts
Give 3 features of osteoclasts
- Multinucleate cells
- Absorb bone - sit in Howship’s lacunae
- Activity is linked to that of osteoblasts
How can bone be differentiated by origin?
Primary (woven) and secondary (lamellar)
How can bone be differentiated by mode of formation?
Membranous and endochondrial
How can bone be differentiated by gross appearance?
Spongy/cancellous & compact or osteons & appositional
How does secondary bone form?
As osteons
What is the structure of secondary bone?
- Central Haversian canal containing blood vessel
- Surrounding concentric rings of lamellar bone with osteocytes
Which bones have intramembranous formation?
Flat bones of the skull and some cortical bone shafts
Which bones have endochondrial formation?
All bones except flat bones of the skull
Where is synovial usually found?
Inside of the joint capsule (1-4 layers of synovial cells)
What is the function of type A synovial cells?
Phagocytic
What is a feature of type B synovial cells?
Rich in rER
How do exocrine glands secrete their products?
Via ducts
How do endocrine glands secrete their products?
Via the blood
What is the only endocrine organ which isn’t epithelial?
The pituitary
Name two hormones which are made in the same tissue
Prolactin and growth hormone
Name two hormones which are made by neural tissue
- Oxytocin and vasopressin
- Made in posterior pituitary
Where is prolactin found?
In lactotrophs, in the anterior pituitary
What is the least common pituicyte?
Thyrotrophs
Give 3 properties of the pineal gland
- Has meninges lying over the top
- Has calcium spread throughout
- Secretes melatonin
Where is calcitonin made?
By the C cells of the thyroid
Where is pepsinogen synthesised?
By the chief cells of the stomach
What do parathyroid chief cells make?
Parathyroid hormone
Where is calcium oxalate found?
In thyroid tissue
Give 4 functions of somatostatin
- Delayed gastric emptying
- Hepatic glycogenesis
- Lowered blood glucose concentration
- Suppression of gastric acid secretion
How is serum calcium concentration regulated?
By parathyroid hormone
Where is ANP made?
In the atrial myocardium of the heart
What does the adrenal zona fasciculate principally secrete?
Cortisol
What is the thickest layer of the adrenal cortex?
The zona fasciculata
Where does the adrenal gland synthesize hormones and with what substance?
- From cholesterol
- Done in the layers of cells near to the surface (adrenal cortex)
Where is the adrenal gland are hormones synthesised from tyrosine?
In the adrenal medulla
What is the endocrine organ which receives its blood supply through a portal circulation?
The anterior pituitary