Histology Flashcards
How does cardiac muscle differ from skeletal muscle?
Structurally- Cardiac muscle is branched, mononuclear, no stem cells, skeletal muscle has nuclei pressed against the membrane
Physiological- Cardiac muscle can contract/ relax without rest, secretes hormones (ANP- when stretched excessively, increased water/Na+/K+ excretion, inhibits RAAS)
What is the function of interrelated discs in the heart?
Desmosomes anchor one cardiac muscle to the next by immediate cytoskeleton filaments
Gap junctions allow ion transfer between cardiac smooth muscle electrochemical coupling
Describe the histology of purkinje fibres
Large modified muscles
Large vacuoles
Few myofibrils therefore pale H&E
Stores of glycogen
Describe the histology of the heart valves
Thick collagen with occasional elastic tissue. Both surfaces are covered with endothelial cells. Chordea tendinae are fibrous
Describe the histology of the pericardium
A single layer of mesothelial cells on the basement membrane with thin loose elastic/ fibrous tissue
Describe the histology of endocardium
A single layer of the heart with endothelial cells on the basement membrane with thin loose elastic/fibrous tissue. This covers the valves
What are the three layers of an artery/vein?
Intima (innermost layer)- endothelial cells on loose connective tisssue with occasional myointimal cells
Media (Middle layer)- Thicker in arteries than veins, made of smooth muscle, elastic and collagen
Adventitia (outermost)- Dense collagen and elastic
What are the features of a muscular artery?
Well defined medial layer of smooth muscle interspersed with elastic.
Wavy internal elastic lamina line at media-Intima divide.
Thick strands of collagen/elastic in adventitia
External elastic lamina only present in large muscular arteries
What are the features of an elastic artery?
Thick medial layer with concentric sheets of elastic interspersed with smooth muscle.
What vessels are elastic artery?
Aorta, GT Vessels
What are the features of arterioles?
3 or fewer layers of muscle in media. No internal elastic lamina. Poor adventitia
What are the features of the glandular acinus in the rectal musosa?
Lined by enterocytes and goblet cells
Mucosa does not ever contain blood vessels
What places have fenestrated capillaries?
Gut, kidney, glomerulus, endocrine glands
What is the diameter of a capillary?
5-10 micrometers (same as an erythrocytes)
Where are contractile pericytes found?
Capillary bed
What are the functions of endothelial cells?
Active transport of molecules across cytoplasm
Influence muscle tone
Coagulation
Produce cell adhesion molecules
What are the features of venules?
Thin walled
Irregular outline
Pericytes alongside them
What are the features of small veins?
Thin layers and poor boundaries
Irregular outline
Large lumen
What are the features of large veins?
Thick wall
Distinct layers
Medial layer with longitudinal smooth muscle
Thick adventitia with longitudinally arranged muscle fibres
What are the walls of lymph vessels?
Connective tissue with some muscle
What are the features of a lymph vessel?
Less pressure than venules
Sometimes lymphocytes seen
No blood
How can reticulocytes be identified on a slide?
Immature erythrocytes with some visible ribosomes (dark staining granules)
How can eosinophils be identified on a slide?
2-3 Lobe nucleus
Bright pink granules
Granular
What are the roles of eosinophils?
Phagocytosis of foreign material especially associated with parasitic infection
Neutralise histamine
How can neutrophils be identified on a slide?
Multi-lobar nucleus
Granular
What are the roles of neutrophils?
Phagocytic
Engulf and destroy bacteria
Leave blood stream to enter tissue at infection site
What are in the primary granules of neutrophils?
Lysosomes, acid hydrolases
What do the secondary granules of neutrophils do?
Regulation of inflammation response
What do the tertiary granules of neutrophils do?
Facilitate insertion of proteins to cell membrane
How can basophils be identified on a slide?
Not multilobar nuclei
Dark blue granules which appear to fill cell
What are the roles of basophils?
Secrete histamine
Similar role to mast cells
How can lymphocytes be identified on a slide?
Small cells with dark staining nucleus and little cytoplasm
B and T are indistinguishable
What are the non granular leukocytes?
Lymphocytes and monocytes
What are the granular leukocytes?
Eosinophils, basophils, neutrophils
How can monocytes be identified on a slide?
Kidney shaped nucleus
No granules
Pale blue cytoplasm
What are the roles of monocytes?
Immature cells which differentiate to one of the various forms when they leave blood
Acute inflammation
Arrive after neutrophils
How can platelets be identified on a slide?
Smaller than erythrocytes
Anucleate
Fragments
Blue
What are platelets formed from?
Fragments from multinuclear megakaryocytes
What are the 4 types of granules in a platelet?
Alpha
Dense
Lysosomes
Peroxisomes
What is respiratory epithelium?
Simple/pseudo-stratified columnar ciliated epithelium with non-ciliated stem cells
Where is respiratory epithelium found?
The nose, nasopharynx, larynx, trachea, bronchi, bronchioles
What are swell bodies and where are they found?
Thin arterioles/venules deep to epithelium in the nose
Why is the skin thin in the nose?
To allow the escape of water
What does the mucous do on the respiratory epithelium?
Preventing dehydration of epithelium and traps particulate matter
Where is the olfactory epithelium found?
The roof of the nose below the cribriform plate
Describe the olfactory epithelium
Pseudo-stratified columnar epithelium with basal and sustenacular cells. Bipolar neurons and serous glands present. Special bowmans glands present
What are bowmans glands?
Small serous glands below olfactory epithelium
What are sustenacular cells?
Tall narrow cells in contact with the basement membrane. Cytoplasm accumulates yellow/brown pigment. Found in olfactory epithelium
What is the epithelium on the vocal folds?
Stratified squamous epithelium
What is the epithelium on the false folds?
Respiratory type epithelium
What is the epithelium on the vestibule?
Respiratory type epithelium
What is the epithelium on the trachea?
Respiratory type epithelium
What is the vocalis muscle?
Voluntary skeletal muscle in the vocal folds
What is the conus elasticus?
A free upper margin of elastic tissue on the vocal folds
What colour do goblet cells stain with H&E?
White
What type of epithelium is present in the bronchus?
Respiratory epithelium
How is the bronchus held open?
Hyaline cartilage framework which appears as isolated islands
Describe the bronchus histology
Respiratory epithelium
Held open by hyaline cartilage
Smooth muscle band under epithelium
Lymph nodules (MALT) at connective tissue
What is a lymph node?
A discrete encapsulated collection of lymphoid tissue
Describe the histology of the bronchioles
Respiratory epithelium Smooth muscle Lymph nodules Closely associated arteries and veins No goblet cells
Describe the histology of the terminal bronchioles
Simple cuboidal epithelium
Sparsely ciliated
Clara cells- function is secretory and synthetic
Sphincter like smooth muscle ring
Describe the histology of the respiratory bronchioles
Simple cuboidal epithelium
Larger than terminal bronchioles
Describe the histology of the alveoli
Respiratory epithelium
Fibroblasts in walls
Adjoining alveoli connected by pores
Type one and type two cells
What is a type one alveolar cell?
Thin cells with flat nuclei
40% population, 90% surface area
What is a type two alveolar cell?
Globular cells secreting surfactants. Rounded dark staining nuclei.
60% population, 10% surface area
What do fibroblasts in alvoli do?
Produce type three collagen (reticulin) and elastic tissue (recoil)
What do alveolar macrophages do?
Free roam in alveoli and phagocytose particulate matter and cell debris. Formed from monocyte in blood.
Where are fixed/septail alveolar macrophages found?
The interstitium between cells and tissue
What type of epithelium is in the mouth?
Stratified squamous non-keratinising epithelium
What type of epithelium is in the oropharynx?
Stratified squamous non-keratinising epithelium
What type of epithelium is in the lip?
Stratified squamous keratinising epithelium
Why is there striated skeletal muscle in the deeper layers of the mouth?
To change shape of the oral cavity
What are fordyce’s spots?
Sebaceous glands in the lip- whitish spots
What type of epithelium is on ventral surface of the tongue?
Stratified squamous non keratinising epithelium
What type of epithelium is on the dorsal surface of the tongue?
Stratified squamous keratinising epithelium
What is found on the upper surface of the tongue?
Connective tissue
Stratified squamous keratinising epithelium
2 types of salivary glands
Large bundles of striated muscle
How do serous glands appear on a slide?
Pink staining- appear as a cluster of grapes with a nucleus on the base
What are the complex folds on the dorsal tongue surface known as?
Papillae
What are the filiform papillae?
The most common papillae. Tall and pointed. On whole anterior two thirds of tongue
What are the fungiform papillae?
Found at the tip and sides of the tongue. Pale staining, spindle shaped taste puds with nerve vesicles
What are the circumvallate papillae?
A V shaped row at the margin of anterior 2/3 and posterior 1/3 of tongue
Describe the histology parotid salivary glands
Striated ducts are surrounded by serous acini
Synthesise alpha-amylase
Secreted via ducts to mouth- Ducts can alter ionic concentrations
Branches of facial nerve pass through gland. Large lymph nodes embedded within gland.
How do parotid secretory cells appear on a slide?
Pyramidal, spherical nucleus, basal cytoplasm full of rough endoplasmic reticulum, apex contains prominent secretory granules (pink staining)
How do parotid duct cells appear on a slide?
Simple cuboidal (stratified at distal end)
Describe the histology of the sublingual salivary gland
Pale staining secretory cells Darker staining duct with simple cuboidal epithelium Flattened oval nuclei to base of cells Branched tubular acinar glands Sticky mucus rich secretion
Describe the histology of the submandibular salivary gland
Well defined
Branched tubulo acinar
Interspersed with fat adipose
Mixed secretion-part mucus part enzyme rich
Serous cells form demi-lunes at closed end of tubules
What is the epithelium on the epiglottis?
Stratified squamous non-keratinising epithelium (respiratory epithelium on lower posterior part)
Describe the histology of the epiglottis
SSNKE (resp epithelium on lower posterior part)
Contains elastic cartilage plate, lymph nodules, and salivary glands
What are the four layers of the GI tract?
- Mucosa
- Sub-mucosa
- External muscle coat (muscularis externa)
- Serosa
What is the GI tract innermost mucosa layer formed of?
Epithelium, lamina propria (connective tissue), and a smooth muscle ring (muscularis mucosa)
What is the GI tract’s sub-mucosa formed of?
Loose connective tissue, glands, lymphoid tissue, blood vessels, meissner’s plexus
What is the GI tract’s musculris externa formed of?
2 layers of smooth muscle, auerbach’s plexus
What is the GI tract’s serosa formed of?
Simple squamous epithelium
What is the muscularis mucosa like in the oesophagus?
Narrow (thicker at gastric end)
What is the epithelium in the oesophagus?
SSNKE above diaphragm, simple columnar below diaphragm
What does the sub-mucosa of the oesophagus contain?
Sero-mucous glands for lubrication, large thin walled veins
What is the muscle of the muscularis externa like in the oesophagus?
Upper 1/3- skeletal
Middle 1/3- Mixed
Lower 1/3- Smooth
What are the folds of mucosa in the stomach called?
Rugae
What is the epithelium in the stomach?
Simple columnar epithelium
How thick is the muscularis externa in the stomach?
3 layers
What are the oblique muscle fibres in the stomach for?
Churning
Where in the stomach are full gastric glands found?
Body and Fundus
Where in the stomach are there no parietal/chief cells found?
Cardia and pylorus
What is the submucosa of the stomach body like?
Loose connective tissue with abundant vessels
Why does the muscularis mucosa of the stomach contain elastic?
To stop stomach collapse on empty
How to parietal cells appear on a slide?
Globular- bright pink with H&E
Cell surface invaginated with many mitochondria
Where in the stomach are parietal cells found?
Gastric glands in the body/ fundus
Upper part of the gland close to the pits
Where in the stomach are chief cells found?
Gastric glands in the body/ fundus
Close to muscularis mucosa
How do chief cells appear on a slide?
Pyramidal
Blue cytoplasm on H&E
Contains granules
Describe the histology of the pyloric region of the stomach
Cardiac and pyloric gastric glands are shorter
Glands are coiled
Mainly mucus neck cells
Scattered with cells producing gastrin
Describe the histology of a villi
Simple columnar epithelium
Short life but replaced by crypt population
Contain venule, arteriole, lacteal, smooth muscle
Describe the histology of a crypt of lieberkuhn
Between villi
Stem cell population
Migrate to the top and shaved off after 5 days
Why does the brush border stain intensely magenta with PAS?
High concentrations of hexose sugars
What are brunner’s glands?
Mucous secreting gland in the submucosa of the duodenum- alkaline secretion that neutralises chyme
Describe the histology of the duodenum
Broad and leaf like villi Few goblet cells Brunner's Glands Long crypts Inner circular layer thicker than outer longitudional layer of muscularis externa
What are paneth cells?
Differentiated cells found at the bottom of crypts that secrete lysozyme and regulate the flora of gut. Bright pink cytoplasmic granules and dark staining nuclei
Describe the histology of the jejunum
Closed packed plicae circularis Many goblet cells Long narrow villi Short crypts Loose submucosa Lymph nodules at lamina propria
Describe the histology of the ilium
Fewer plicae and shorter villi due to lesser absorption
Goblet cells increase towards distal end
Large peyers patches at submucosa
Simple squamous serosa on edge of longitudional muscle
What is the epithelium of the appendix?
Simple columnar epithelium
Describe the histology of the appendix
Simple columnar epithelium Goblet cells Simple crypts No muscular mucosa Fat filled Lamina propria and submucosa full of lymphoid tissue
Describe the histology of the colon
Little folding with no villi Mucosa contains close-packed crypts with abundant goblet cells and enterocytes Prominent muscularis mucosa Lots of lymph in mucosa and submucosa Taeniae coli
What is the epithelium in the anal canal?
Stratified squamous epithelium, keratinised at distal end
Describe the muscularis externa in the anal canal
Smooth muscle of muscularis externa is thickened and surrounded by striated muscle of external anal sphincter
What are the functions of the hepatocytes?
Creation/store energy as gycogen and fat
Synthesise plasma proteins
De-amination of amino acids and production urea
Uptake, synthesis, excretion of bilirubin and bile acids
Detox and inactivation of drugs by oxidation
What are the four lobes of the liver?
Left
Right
Caudate
Quadrate
What is the blood supply to the lobules?
70% Portal vein blood
30% portal artery blood
What are sinusoids?
Wide, thin, fenestrated capillaries
What is in the portal triad?
Hepatic artery, hepatic vein, bile duct
What is the epithelium of a bile ductule?
Simple cuboidal epithelium
What is space of disse?
Area in liver- no blood here but plasma
Describe the histology of the sinusoids
Endothelial cells interspersed with kupffer cells and ito cells
Sit on a meshwork of reticulin
Separated from hepatocyte cords by space of disse
What are kupffer cells?
Fixed macrophages in the lining of sinusoidal endothelium. Phagocytose blood borne pathogens
Describe the histology of the gallbladder
Simple columnar with poor brush border Adapted for water reabsorption Epithelium thrown into folds Gallstones may be present at lumen Large veins in walls Smooth muscle at outer surface Serosa visible at top
How are the pancreatic enzymes activated?
Alkaline environment of duodenum
How is the exocrine pancreas stimulated to secrete alkaline fluid from centro-acinar and small duct cells?
Secretin
What is the pacinian corpuscle?
The pressure sensor in the pancreas
What is the epithelium in the exocrine pancreas?
Simple cuboidal epithelium
Give 3 examples of fixatives that can be used to fix a specimin
Formalin
Alcohol
Acid
What is used to dehydrate tissues?
Alcohol
How thick are the slices of specimins?
2-10 micrometres
How are blood samples viewed histologically?
Smears
What does haematoxylin stain?
Nuclei and RNA = blue
What does eosin stain?
Cytoplasm, fibres, colloidal protein= Pink
Keratin= Orange/Red
What does iron haemotoxylin stain?
Nuclei and elastic fibres= Black
What does alcian blue stain?
GAG-rich structures, mucous goblet cells, mast cell granules, cartilage, matrix= Blue
What does Period acid schiff stain?
Hexose sugars= Magenta
What does Perl’s stain stain?
Ferric iron= Prussian blue
What does Romanovsky stains stain?
Chromatin, azyrophils, neutrophils granules= purple
Erythrocytes= Red/Pink
Eosinophil granules= Pale blue
Lymphocyte and monocyte cytoplasm, basophil granules= Dark blue
What does Toluidine blue stain?
Nuclei, ribosomes = Dark blue
Cytoplasm, cartilage, matrix= pale blue
Mat cell granules, GAG rich components= Bright purple
What does Van gieson stain?
Collagen= Pink/Red Cytoplasm= Yellow/Green Nuclei= Black
What are all the 6 cell shapes?
Rounded Polygonal Fusiform Squamous Cuboidal Columnar
What are the 5 tissue types?
Epithelia, muscle, supporting tissue, nerves and germ cells
What is the difference between euchromatin and heterochromatin?
Euchromtin is lightly packed and heterochromatin is tightly packed
Where is the site of lipid synthesis?
The mitochondrial outer membrane and smooth ER
Where is the site of the ETC chain?
The mitochondrial inner membrane
Where is the site of the Krebs cycle?
The mitochondrial matrix
Where is the site of nucleotide phosphorylation?
The intermembranous space of the mitochondria
Where is the site of protein synthesis?
Rough ER
Where is the site of proteolysis?
Trans golgi network
Where are vesicles recieved?
The cis face of the golgi
Where are olgiosaccharides formed?
The medial golgi
What is the role of perioxiomes?
Oxidise long chain fatty acids
What is lipofuscin?
An orange-brown pigment from peroxidation of lipids in older cells- common in heart and liver of older patients
How long are tubulin proteins?
25nm
How long are actin microphilaments?
5nm
How long are intermediate filaments?
10nm
Where is simple squamous epithelium found?
Blood vessels, the outside of the lungs, abdominal organs
Where is simple cuboidal epithelium found?
The kidney tubules, small ducts
Where is simple columnar epithelium found?
The stomach, intestines and uterus
What filaments are microvilli formed of?
Actin and Myosin
What filaments are cilia formed of?
Tubulin and dynein
Where is stratified epithelia found?
Sites of abrasion- skin, vagina, mouth
Where is stratified squamous non-keratinising epithelium found?
Mouth, oropharynx, vagina
Where is stratified squamous keratinising epithelium found?
The skin
What does keratin do to an epithelium?
Waterproof it
Where is pseudostratified epithelium found?
The conducting airways
What types of epithelium can have cilia?
Simple columnar epithelium, pseudostratified epithelium
What extra-cellular proteins are present in a basement membrane?
Collagen IV and fibronectin
What stain will make basement membranes visible?
PAS
What are occluding (tight) junctions?
Band-like fusions between cells that are impervious to most molecules
What are desmosomes?
Plaques that form physical joints between cells and connect the cytoskeletons of adjacent cells
What are gap junctions?
Electrical junctions that permit the transfer of small molecules
What is the origin of connective tissue cells?
- Usually undifferentiated mesenchymal cells e.g. fibroblasts
- Some from haematopoetic stem cell line e.g. monocytes
What molecules are present in the ground substance?
Proteogylcans, GAG, Invisible fibres like laminin
What is collagen secreted from?
Fibroblasts
Are collagen fibres produced extracellularly or intracellularly?
Extra-cellularly
Where is type I collagen normally found?
Skin and bone
Where is type II collagen normally found?
Cartilage
Where is type III collagen normally found?
Liver, bone marrow, spleen (reticulin)
Where is type IV collagen normally found?
Basement membrane
Where is type V collagen normally found?
Placenta
How is collagen viewed on H&E?
Extracellular fibres that stain pink. Variable thickness and length. Often run in bundles
What is loose connective tissue comprised of?
Widely spaced, thin collagen fibres and the fibroblasts that secrete them. Inbetween this is unstained ground substance
What is dense connective tissue comprised of?
Densely packed thick collagen fibres, and the fibroblasts that secrete them. Some unstained ground substance
What are the two types of dense connective tissue?
Regular and Irregular
Where is regular dense connective tissue found?
Tendons
Where is irregular dense connective tissue found?
Fascia of penis
What is reticuin?
Type III collagen- forms a supporting scaffold in many organs e.g. bone marrow, liver, kidney, spleen
What stain is used for reticulin?
Silver stain
What is elastin?
Elastic tissue containing fine fibres and sheets of elastin. It is produced by fibroblasts.
What stain is used for elastin?
H&E
Describe the histological appearance of white adipose tissue
Large cells with a single fat globule in each cell which pushes the cytoplasm and nucleus to the edge. Usually appears empty in slides as fat is extracted in processing
Where is brown adipose tissue found?
Across the shoulders and down the back of newborns- important in neonatal thermoregulation (generates heat on breakdown)
What is the difference between brown and white adipose tissue?
Brown has many globules of fat per cell, white only has one globule per cell.
Brown is only found in newborns, white is found in adults
Describe the histological appearance of brown adipose tissue
Many fat globules per cell, with multiple vacuoles. Generally a pink “foamy” appearance
What cells are found in cartilage?
Chondroblasts and chondrocytes
Is cartilage vascular or avascular?
Avascular- derives its blood supply from vessels either side of the cartilage
Where is hyaline cartilage found?
Synovial joints
Describe the histological appearance of hyaline cartilage
Chondrocytes in lacunae surrounded by a glassy amorphous blue/grey matrix with no visible fibres
Where is elastic cartilage found?
The pinna of the ear and the epiglottis
What is found in the the perichonrium of hyaline, elastic and fibrocartilage?
Fibroblasts and collagen
Describe the histological appearance of elastic cartilage
Visible elastic fibres in a blue/grey matrix
What stain is used for elastic cartilage?
H&E can be used, but it is more visible with silver stain
Where is fibrocartilage found?
Annulus fibrosis of spine and pubic symphysis
Describe the histological appearance of fibrocartilage
Visible collagen fibres in matrix
Where is synovium found?
The inside of the joint capsule
How many layers of synovial cells are in the synovium?
1-4 layers
What are the type A and type B cells in synovium?
Type A- phagocytes
Type B- cells rich in rER that secrete synovial fluid
Is synovium vascular or avascular?
Richly vascular
Where is smooth muscle found?
The walls of blood vessels, tube of intestine and bronchioles
Describe the histological appearance of smooth muscle
Individual cells with oval/ circle nucleus
Set in eosynophilic cytoplasm with no striations
State the layers of an artery wall going from lumen outwards
- Lumen
- Endothelium
- Basement membrane
- Intima
- Internal elastic lamina
- Media
- External elastic lamina
- Adventitia
What is the intima?
A thin layer of connective tissue- the next layer after the lumen
What is the media?
A thick layer of connective tissue, generally comprising of smooth muscle with some fibroblasts, and variable amounts of collagen and elastin
What is the internal elastic lamina?
A layer of elastic tissue bounding the intima
What is the adventitia?
The final layer of an artery wall, formed of loose elastic tissue
Name an elastic artery
The aorta
Describe the media of an elastic artery
A thick layer of connective tissue, containing abundant concentric sheets of elastin
Are most arteries muscular or elastic?
Muscular
Describe the media of a muscular artery
A thick layer of connective tissue, comprising of smooth muscle and has a little elastin
Name two muscular arteries
The radial artery and the splenic artery
How can arterioles be distinguished from arteries?
Arterioles are arbitrarily defined as having 3 or fewer muscle layers in their media or being up to 100 micrometres in diametre.
In the arterioles the elastic laminae is poorly defined
What are pericytes?
A layer of cells on the outside of capillaries and venules which regulate their size
What is a fenestrated capillary?
When the endothelial layer is incomplete. This facilitates movement in and out of capillaries.
What are the layers of a capillary wall
Endothelium
Basement membrane
Pericyte
Where are fenestrated capillaries found?
The kidneys and liver
What is the difference between a vein’s wall and an artery’s wall?
A vein has a wider lumen and thinner media. Veins also have no external elastic lamina.
What are pericytes replaced with as venules become veins?
Smooth muscle
Is the smooth muscle in veins circular or longitudional?
Can be either !
What vessels have valves?
Veins and lymphatics
What does lymphatics contain?
Eosinophilic lymph (fluid derived from plasma) and may contain lymphocytes
What cells produce myelin?
Schwann cells
What is endoneurium?
Connective tissue present between individual axons
What is perineurium?
Connective tissue surrounding groups of axons to form fasicles
What is epineurium?
Connective tissue binding fasicles to form nerve fibres
What stain can be used for myelin?
Silver stain
What is myelin?
A spiral of apposed schwann cell membranes that insulate the axon
What are nodes of ranvier?
Gaps between schwann cells that allow for saltatory conduction
Where are the cell bodies of motor neurons found?
In the grey matter of the spinal cords
Where are the cell bodies of sensory neurons found?
The dorsal root gangion
Where are the cell bodies of sympathetic neurons found?
In the grey matter of the spinal cord and in adjacent sympathetic ganglia
Where are the cell bodies of parasympathetic neurons found?
The brain and local ganglia of organs
What are the four principle components of the urinary tract?
Kidneys
Ureters
Bladder
Urethra
How many nephrons are approximately in one kidney?
One million
What are the 6 components of the nephron?
Proximal convoluted tubule Thick limb loop of henle Thin limb loop of henle Glomerulus Distal convoluted tubule Collecting duct
What are the 3 layers of the kidney?
Cortex
Medulla
Pelvis
What aspects of the nephron are primarily found within the cortex of the kidney?
Glomeruli
Proximal convoluted tubule
Distal convoluted tubule
Medullary rays
What is a medullary ray?
A collection of loops of henle and collecting duct that have their renal corpuscles in the outer part of the cortex (because their glomerulus is at the very outer aspect of the cortex)
What aspects of the nephron are primarily found within the medulla of the kidney?
Loops of henle, collecting ducts, and blood vessels
What is a glomerulus?
A tuft of convoluted fenestrated capillaries, supported by mesangial cells and encased within the Bowman’s capsule
What layers will molecules have to get through to get from the glomerulus to the bowman’s capsule?
The capillary endothelium, the double thickness glomerular basement membrane, the foot processes of the podocytes
What are the two cell types found at the glomerulus?
Capillary endothelial cells and mesengial cells (lie inbetween the capillaries)
What stain can be used to see the glomerular basement membrane?
Periodic acid schiff (PAS)
What is the role of the mesangial cells in the glomerulus?
Provide structural support for the capillary, and are formed of smooth muscle so can contract to narrow capillaries and reduce the glomerular filtration rate.
Also involved in the phagocytosis of glomerular breakdown products.
What are the layers of the glomerular basement membrane?
Lamina lucida interna
Double thickenss lamina densa
Lamina lucida externa
Why are Heparan sulfate molecules found in the glomerular basement membrane?
To repel negatively charged ions in the plasma
What are the two components associated with the juxtaglomerular apparatus?
The afferent arteriole and distal convoluted tubule
How is the afferent arteriole associated with the juxtaglomerular apparatus?
It contributes granular cells that secrete renin in response to low blood pressure
How is the distal convoluted tubule associated with the juxtaglomeruar apparatus?
It contributes the macula densa, which is a patch of closely packed endothelial cells along a tubule. They sense NaCl conc and regulate tubuloglomerular feedback.
What are the three cell types present in the juxtaglomerular apparatus?
Lacis cells
Macula Densa
Granular cells
Describe the histological appearance of the proximal convoluted tubule
Cuboidal epithelium rings with round central/basal nuclei. Very prominent brush border of microvilli in the luminal surface, and many mitochondria so appears eosinophilic.
What is the role of the proximal covoluted tubule?
Reabsorption of NaCl proteins, polypeptides, amino acids, glucose
What is the difference between the epithelium of the thin and thick segments of the loop of henle?
Thin- simple squamous
Thick- Low cuboidal
Describe the histological appearance of the distal convoluted tubule
Low cuboidal epithelium rings with scanty microvilli- no prominant brush border. Numerous mitochondria.
What is the role of the distal convoluted tubule?
Regulates acid base by secreting H+ and absorbing HCO3- (Via cellular carbonic anhydrase). Reguates Na level by exchanging Na for K- mediated by aldosterone.
How can you tell a collecting duct apart from the loop of henle?
The collecting duct has cuboidal epithelium, which is much plumper than that of the loop of henle, and has round, central nuclei
What is the role of collecting duct?
Water reabsorption, sodium balance and acid base balance.
What are the two types of epithelial cell present in the collecting duct?
Principal cell and intercalated cells
What is the role of the principal cells of the collecting duct?
To respond to aldosterone and ADH for water reabsorption (insertion of aquaporin 2)
What is the role of the intercalated cells of the collecting duct?
To exchange H+ for HCO3-
What is the order of divisions of the kidney’s blood supply?
Abdominal aorta-> Renal artery at L1 -> Anterior and posterior division -> interlobar artery -> arcuate artery -> Interlobular artery -> Afferent arteriole -> glomerulus-> Efferent arteriole -> Peritubular capillaries -> Vasa recta
What is the epithelium of the renal pelvis?
Urothelium
What is the role of the renal pelvis?
Transmits filtrate from nephron to ureter
Describe urothelium
Complex stratified epithelium- A layer of umbrella cells overlying a pseudostratified layer of polygonal cells
What are the 3 layers of urothelium?
- Large dome-shaped umbrella cells
- Intermediate layer
- Basal layer- cuboidal cells
In the GI tract, is the muscle circular on the inner or outer layer?
Circular on the inner layer
In the ureter is the muscle circular on the inner or outer layer?
Circular on the outer layer
Do ureters have a serosa?
No
What are the layers of the bladder?
Urothelium Lamina propria (poorly developed) Muscularis mucosa Submucosa (Well developed) Muscularis propria Subserosa and serosa
How many muscular layers are there in the muscularis propria of the bladder?
3
How long is the urethra in females?
4-5cm
What is the epithelium of the female urethra?
Proximally- urothelium
Distally- Non-keratinising squamous epithelium
What glands open into the female urethra?
Paraurethral and periurethral
How long is the male urethra?
15-20cm
What are the three parts of the male urethra?
- Prostatic urethra (3cm)
- Membranous urethra (1cm)
- Penile urethra (16cm)
What is the epithelium of the male urethra?
Prostatic and membranous urethra- urothelium
Penile urethra- Pseudostratified epithelium proximally and stratified squamous epithelium distally.
What is the average weight of the testis?
15-19g
What are the three layers that form the capsule around the testis?
- Tunica vaginalis
- Tunica albuginea
- Tunica vasculosa
What is the tunica vaginalis in men?
Two layers (parietal and visceral) of flattened mesothelial cells forming the outside of the capsule of the testis
What is the tunica albuginea in men?
A thick fibrous layer of the testi’s capsule- contains collagen fibres with some fibroblasts, myocytes and nerve fibres
What is the tunica vasculosa in men?
The thin innermost layer of the testi’s capsule- contains loose connective tissue containing blood vessels and lymphatics
Where do spermatazoa form?
The seminiferous tubules
What is the route of spermatazoa from seminiferous tubule to outside the body?
Seminiferous tubule Straight tubules Reti testis Efferent ducts Epididymis Vas deferens Ejaculatory duct Urethra
How many lobules are there roughly in the testis?
250
What does the septa between lobules of the testis form from?
The capsule of the testis
How many seminiferous tubules are there per lobule?
1-4
What are the three types of spermatogonia?
Type A darkly stained cells
Type A pale stained cells
Type B differentiating cells
What is the role of type A dark cells in the testis?
Stem cell population
What is the role of type A pale cells in the testis?
Develop into type B cells
Describe the histological appearance of type B cells in the testis
Spherical nuclei with densely stained masses of chromatin
What is the order of development of sperm?
Spermatogonia Primary spermatocytes Secondary spermatocytes Spermatids Spermatozoa
Where are sertoli cells found?
Resting on the basement membrane of the seminiferous tubule
Describe the histological appearance of sertoli cells
Columnar cells with irregularly shaped nuclei; folded and with a prominent nucleolus. Eosinophilic cytoplasm
What are the roles of sertoli cells?
Supportive, phagocytic and secretory functions- androgen binding protein and inhibin
What structures are present in the head of the spermatozoa?
Acrosomal cap and nucleus
What structures are present in the midpiece of the spermatozoa?
Spiral mitochondria wrapped around an axoneme
What structures are present in the tail of the spermatozoa?
Neck- centrioles
Axoneme surrounded by a plasma membrane
Where are leydig cells found?
Singly or in clusters in the interstitium between seminiferous tubules
What are the roles of leydig cells?
Secrete testosterone
Describe the histological appearance of leydig cells
Cells with abundant cytoplasm containing lipid containing reinke’s crystalloids (intracytoplasmic eosinophilic crystalloids found after puberty)
What is the rete testis?
An anastamosing network of tubules at the hilum of the testis that receive luminal contents from seminiferous tubules
Describe the histological appearance of the rete testis
Tubules lined by simple squamous or low columnar epithelium on a relatively thick basement membrane. Have cilia at the luminal surface.
What are the roles of the rete testis?
- Mixing chamber for contents of the seminiferous tubules
- Reabsorption of protein from luminal contents
How many efferent duct are present in the testis?
12-15
Describe the histological appearance of the efferent ducts of the testis
Ducts lined by ciliated and non ciliated simple columnar epithelium with interspersed cuboidal basal cells giving a pseudostratified appearance
How long is the epididymis?
4-5cm but highly convoluted so roughly 5m in tubular length
Describe the histological appearance of the epididymis
Tube, lined by tall columnar cells with long atypical cilia. The epithelium is supported by a thick basement membrane, surrounding which is a well defined muscular coat
What are the roles of the epididymis?
- Absorption of testicular fluid
- Phagocytosis
- Production of secretions for spermatozoa maturation
How long is the vas deferens?
30-40cm
Describe the histological appearance of the vas deferens
Tube lined by pseudostratified columnar epithelium comprising columnar and basal cells. Thick muscular wall of 3 layers
What are the lobes of the prostate?
Anterior, middle, posterior and two lateral
What are the regions of the prostate?
Peripheral, central, transitional and peri-urethral gland regions
How many acini are present within the prostate?
30-50 tubuloalveolar glands with convoluted edges
What cells line the acini of the prostate?
Secretory cells, basal cells (form a continuous layer) and neuroendocrine cells
What do secretory cells of the luminal side of the prostate gland secrete?
Phosphate-specific antigen, Acid phosphotases, citric acid, amylase, and other proteins
What is the role of phosphate specific antigen?
Liquifies semen after ejaculation
What structures are present in the stroma of the prostate?
Smooth muscle, fibroelastic fibres, blood vessels and nerves
What cell type lines the seminal vesicles?
Tall non-ciliated columnar epithelium, containing vacuoles and lipofuscin
How much of the ejaculate is formed of seminal vesicle secretion?
70-80%
What does seminal vesicle secretion contain?
Fructose, prostaglandins, proteins, amino acids, citric acid and vitamin C
What is the role of the seminal vesicle?
Produce secretion to act as nutrients for the spermatozoa
Where does the seminal vesicle duct drain into?
The ejaculatory duct
What are the 3 components of the erectile tissue?
2 x Corpora cavernosa
Corpus spongiosum
What is the corpora cavernosa?
Two richly vascular components of erectile tissue lying within the dorsal side of the penis.
What is the copus spongiosum?
A component of erectile tissue on the inferior side of the penis and surrounding the urethra.
Describe the histological appearance of erectile tissue
Irregular vascular spaces seperated by fibroelastic tissue and smooth muscle
How is the ovary attached to the broad ligament?
The mesovary
How is the ovary attached to the uterus?
The utero-ovarian ligament
How is the ovary attached to the pelvic wall?
The suspensory ligament
What is the outside layer of the ovary like?
A single layer of modified mesothelium
What is the tunica albuginea in a female?
A poorly defined connective tissue layer in the ovary
In which layer of the ovary are the ovarian folicles found?
The cortex
Describe the histological appearance of the ovarian cortex
Spidle stromal cells arranged in whorls with ovarian follicles and some leutinised cells
Describe the histological appearance of the ovarian medulla
Loose fibroelastic tissue with blood vessels, lymphatics and nerves.
What is the rete ovarii?
An analogue of rete testis- present at the hilum of the ovary
Where are primordial follicles found?
At the periphery of the cortex
What is a primordial follicle made of?
A primary oocyte in a resting state, surrounded by a single layer of squamous epithelial cells (granulosa cells)
In the menstrual cycle, how many primordial follicles begin to develop?
30-40
What hormone controls the development of a primordial follicle into a primary follicle?
FSH from the anterior pituitary
What changed happen to a primordial follicle when it becomes a primary follicle?
- Oocyte enlarges
- Follicular epithelial cells proliferate (granulosa cells)
- Stromal cells become organised into connective tissue sheath
- Zona pellucida forms directly around the oocyte
What changes happen to a primary follicle when it becomes a secondary follicle?
- Formation of the antrum (space filled with follicular fluid)
- CT differentiates into inner Theca interna and outer Theca externa
- Oocyte is supported in the antrum by a stalk of granulosa cells (cumulus oophorus)
What is the the name of the stalk of granulosa cells that supports the oocyte in the antrum in a secondary follicle?
Cumulus oophorus
What are the two layers of connective tissue in a secondary ovarian follicle?
Theca interna and theca externa
What is the Theca interna of a secondary follicle?
The inner layer of stroma, comprising of stromal cells which have enlarged and contain lipid
What do the stromal cells of the theca interna secrete?
Oestrogen
What is the theca externa of a secondary follicle?
The outer layer of the stroma comprising small stromal cells
What is the corona radiata in a graafian follicle?
A layer of granulosa cells surrounding the oocyte
What surrounds the ovum in a graafian follicle?
A thick zona pellucida
How many primordial follicle are present at birth?
Approximately 1 million
What hormone triggers ovulation?
Leutinising hormone
What is leutinisation?
When the granulosa and theca cells become polygonal, bigger in size and have abundant cytoplasm containing lipid- occurs in the corpus luteum
What does the secondary follicle develop into after ovulation?
Corpus luteum
What hormones does the corpus luteum secrete?
Progesterone and oestrogen
How many days after ovulation does regression of the corpus luteum occur?
8-9 days
What characteristic changes occur to the corpus luteum during regression?
- Granulosa cells decrease in size, develop pyknotic nuclei and accumulate abnormal lipid
- Cells undergo dissolution and are phagocytosed
- There is progressive fibrosis by ingrowth of connective tissue
What does the corpus luteum regress into?
The corpus albicans
What is the histological appearance of the corpus albicans?
A well circumscribed structure with convoluted borders, almost entirely composed of densely packed collagen with occasional follicles
What are the roles of the fallopian tube?
To transport the ovum to the uterus
To be the site of fertilisation
In which ligament does the fallopian tube run?
The broad ligament
What are the 4 segments of the fallopian tube?
- Intramural (inside uterine wall)
- Isthmus (2-3cm, thick walled)
- Ampulla (Expanded area)
- Infundibulum (trumpet shaped opening to peritoneum, has fimbriae)
What are the branching folds of the mucosa of the fallopian tubes called?
Plicae
What are the two cell types in the mucosa of the fallopian tube?
Secretory and ciliated
Is the inner muscularis layer of the fallopian tube circular or longitudional?
Circular
At which end of the fallopian tube are ciliated cells more prominant?
The ovarian end
What are the three layers of the wall of the uterus?
Endometrium
Myometrium
Serosa
What are the two layers of the endometrium of the uterus?
A deep basal layer- stratum basalis
A superficial functional layer- Stratum compactum (towards the surface) and stratum spongiosum
What layer of the uterus is shed in menstruation?
The stratum spongiosum of the endometrium
What hormone stimulates the proliferative phase of the menstrual cycle?
Oestrogen
How can the endometrium of the proliferative phase of the menstrual cycle be recognised histologically?
Straight proliferating glands with mitotic activity, no luminal secretions, stromal cells are spindled and compact
What hormone stimulates the secretory phase of the menstrual cycle?
Progesterone
How can the endometrium of the early secretory phase be recognised?
The epithelial cells of the endometrial glands contain vacuoles of glycogen
How can the endometrium of the mid secretory phase be recognised?
The epithelial cells of the endometrial glands contain glycogen vacuoles above and below the nucleus and later intraluminal secretions. Glands are more rounded, stroma-oedema.
How can the endometrium of the late secretory phase be recognised?
Elongated and saw-toothed endometrial glands with more intraluminal secretions. The stroma has spiral arterioles and decidual change.
How can the endometrium of the menstrual phase be recognised?
Stromal haemorrhage and granulocytes
Stromal and glandular fragmentation
What triggers the menstrual phase?
Progesterone stimulation being withdrawn
What are the different phases of the endometrium in the menstrual cycle?
Proliferative
Secretory (early, mid, late)
Menstrual
What is the muscular wall of the uterus?
Myometrium- 3 ill defined smooth muscle layers
Inner longitudinal, middle circular, outer longitudinal
What are the two components of the cervix?
Endocervix and ectocervix
Describe the histological appearance of the endocervix
Loose fibromuscular stroma lined by simpled columnar ciliated epithelium, thrown into crypts
Describe the histological appearance of the ectocervix
Dense smooth muscle stroma lined by non-keratinised stratified squamous epithelium
What is the site of the cervix which most cervical cancers occur?
The transformational zone (squamocolumnar junction)
What epithelium lines the vagina?
Non keratinising stratified squamous epithelium
How many muscular layers are there in the vagina?
2- inner circular and outer longitudinal
What epithelium lines the labia majora?
Keratinising stratified squamous epithelium with skin adnexae
What epithelium lines the labia minora?
Non-keratinising stratified squamous epithelium
What are bartholin’s glands?
Tubuloalvolar glands in the vulva. Acini are lined by mucus-secreting epithelium
What are minor vestibular glands?
Simple tubular glands lined by mucus-secreting epithelium in the vulva
What are skein’s glands?
Female analogous to the prostate, lined by pseudostratifeid columnar epithelium
What epithelium lines the hymen?
Non-keratinising squamous epithelium
What is the clitoris?
Erectile tissue rich in blood vessels and nerves
What are the functions of the skin?
- Barrier to infection
- Waterproofing
- Thermoregulation
- Protection against trauma
- Protection against UV- light
- Vitamin D synthesis
- Sensation
What is the outermost layer of the skin?
The epidermis stratum corneum
What are the layers of the epidermis?
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum corneum
What are the two types of cells present in the stratum basale?
Basal epithelial cells (Stem cell population)
Melanocytes (Produce melanin)
In which layer of the skin are melanocytes found?
The basal layer of the epidermis
What is the approximate density of melanocytes?
1000-2000 per mm^2
Where does melanin get transferred to after being synthesised?
To keratinocytes in melanosomes
What hormones trigger the production of melanin?
MSH and ACTH
What is the role of melanin?
To absorb ultraviolet light, protecting us from non-ionising radiation damage
What alters the colour of someone’s skin?
The amount and type of melanin synthesised (NOT the number of melanocytes)
Which layer of the epidermis is the largest?
Stratum spinosum
What cells are present in the stratum spinosum?
- Plump, polygonal keratinocytes with prominant intracellular adhesion
- Langerhans cells- antigen recognition
- Merkel cells- Sensory
What cells are present in the stratum granulosum?
Flattened squames with an eosinophilic cytoplasm, containing haematoxophilic kerato-hyaline granules
In which layer of the skin is keratin synthesised?
The stratum granulosum
Describe the stratum corneum
The outermost acelullar layer of the skin with plates of keratin- thicker in the palms and soles of the feet (5 layers rather than 4 layers)
What is the extra layer in the epidermis found between the stratum corneum and stratum granulosum at sites of abrasion?
Stratum lucidum
What are epidermal adnexae?
Downgrowths of the epidermis into the dermis
What is found within the epidermal adnexae?
Hair follicles
Sebaceous glands
Eccrine sweat glands
Apocrine sweat glands
Where are sebaceous glands found?
Accompanying hair follicles
What do sebaceous glands secrete?
Holocrine secretion (whole cells)- produces sebaceous secretion which lubricates and waterproofs hairs
Where are apocrine glands found?
Armpit, groin, genitals, around the anus, in the ear - accompanying hair follicles
Describe the histological appearance of apocrine glands
Simple, coiled, tubular glands, with an eosinophilic cytoplasm- with surface budding
What do apocrine glands secrete?
An apocrine secretion- elements of the cytoplasm of the cells- pheromones ??
What are the commonest type of sweat glands?
Eccrine glands
What do eccrine glands secrete?
An eccrine (merocrine- exocytosis) secretion- thin and watery
Described the histological appearance of eccrine glands
Coiled tubes, 2 cell layers thick- inner layer is secretory, outer layer is myoepithelial
Where are eccrine sweat glands found?
Everywhere
What are rete pegs/ridges?
Where the epidermis protrudes downwards into hte underlying dermis at the dermo-epidermal junction
What is the papillary dermis?
The space between the rete pegs
What is the thickest layer of the dermis?
The reticular dermis
Where are the blood vessels and nerves of the skin found?
The dermis
What is found within the dermis (8)?
- Irregular loose connective tissue
- Fibroblasts
- Collagen
- Glycosaminoglycan matrix
- Blood vessels and lymphatics
- Nerves
- Sensory cells
- Scattered inflammatory cells
What can Meissner’s corpuscles detect?
Fine touch
How long are meissner’s corpuscles?
30-140 micrometres
What are meissner’s corpuscles?
Encapsulated unmylenated nerve endings that detect fine touch
Where are meissner’s corpuscles found?
In the dermal papillae (especially in hairless skin)
Describe the appearance of pacinian corpuscles
Large (1-4mm) long encapsulated sensory receptors- appear as concentric rings
Where pacinian corpuscles found?
In the deep dermis
What can pacinian corpuscles detect?
Vibration and tickle
What is the subcutis formed of?
Adipose tissue and fibrovascular septa
What are the roles of the subcutis?
Insulation
Shock-absorber
Food store
Where do all the ducts of the breast empty?
At the nipple
Describe the terminal duct lobular unit of the breast
Lobules arranged around a terminal duct, set in loose fibrous connective tissue
What layers of cells line the ducts and lobules of the breast?
An outer myoepithelial layer
An inner columnar epithelial layer (Can adapt to produce milk)
What are the common features of the endocrine organs?
- Glandular epithelium
- Richly vascularised
- Secrete a variety of hormones
- Controlled by positive and negative feedback loops
What does the posterior pituitary store/secrete?
Oxytocin
Antidiuretic hormone
Describe the histology of the anterior pituitary
Nested epithelial pituicytes in a richly vascular fibrous stroma. There are several different types of pituicyte but these are not distinguishable on H&E
What percentage of pituicytes are somatotrophs and what do they secrete?
50%
Growth hormone
What percentage of pituicytes are lactotrophs and what do they secrete?
25%
Prolactin
What percentage of pituicytes are corticotrophs and what do they secrete?
15-20%
ACTH, alpha-MSH, beta-lipotrophin, beta-endorphin
What percentage of pituicytes are gonadotrophs and what do they secrete?
10%
FSH and LH
What percentage of pituicytes are thyrotrophs and what do they secrete?
1%
Thyroid stimulating hormone
What stain allows you to see the nests of pituicytes within the anterior pituitary?
Reticulin stain
Where are somatotrophs normally found within the anterior pituitary?
Primarily at the lateral wings, but can be found throughout
Describe the histological appearance of lactotrophs
Polygonal cells with cytoplasmic processes that wrap around other cells
Describe the histological appearance of thyrotrophs
Elongated cytoplasmic processes, that don’t wrap around other cells
Describe the histological appearance and staining of gonadotrophs
Scattered round/oval cells that stain with either alpha subunit, beta LH or Beta FSH
Describe the histological appearance and staining of corticotrophs
Round basophilic cells with large cytoplasmic vacuoles- enigmatic bodies. Tend to stain dark purple on H&E.
Where are corticotrophs most likely to be found within the anterior pituitary?
The median of the gland
What are susetentacular cells?
Supporting cells within the anterior pituitary that surround the normal follicles - S100 +ve
What does the pineal gland secrete?
Melatonin
How are the cells in the pineal gland arranged?
Pinealocytes are arranged in rosettes- a loose ring with central tissue and processes leading to a central capillary
What is brain sand?
Areas of accumulation of calcium within the pineal gland
What cells are present within the thyroid?
Follicular cells with colloid, and C cells
What hormones does the thyroid produce?
Thyroxine and calcitonin
What do thyroid follicular cells secrete?
Colloid and thyroxine
What do follicular C cells secrete?
Calcitonin
How many parathyroid glands are there usually?
4
What hormone does the parathyroid glands secrete?
Parathyroid hormone (PTH)
What are the three cell types present in the parathyroids?
Chief cells
Oxyphils
Adipocytes
Describe the histological appearance of the parathyroid chief cells
Small polygonal cells with scant cytoplasm. No calcium oxalate crystals (unlike thyroid)
What is the role of the parathyroid’s chief cells?
To secrete PTH, which raises the serum calcium using the bone, kidney and gut
Describe the histological appearance of the parathyroid oxyphil cells
Large polygonal cells, that increase with age. Abundant eosinophilic cytoplasm that is finely granular.
Where are the islets of Langerhans most prevalent?
The pancreatic tail
Describe the histological appearance of the Islets of Langerhans
Large, pale staining balls of cells with a thin fibrous capsule
What are the four cell types within the endocrine pancreas?
Beta cells
Alpha cells
Delta cells
PP cells
What percentage of cells in the endocrine pancreas are beta cells and what do they secrete?
70%
Insulin
What percentage of cells in the endocrine pancreas are alpha cells and what do they secrete?
20%
Glucagon
What percentage of cells in the endocrine pancreas are delta cells and what do they secrete?
5-10%
Somatostatin
What percentage of cells in the endocrine pancreas are PP cells and what do they secrete?
1-2%
Pancreatic polypeptide
What are the three layers of the adrenal cortex (outside to inside)?
Zona glomerulosa
Zona fasciculata
Zona reticularis
What does the zona glomerulosa of the adrenal cortex secrete?
Mineralocorticoids - Aldosterone
What does the zona fasiculata of the adrenal cortex secrete?
Glococorticoids- Cortisol
What does the zona Reticularis of the adrenal cortex secrete?
Androgenic steroids
Which layer of the adrenal cortex is the thickest?
Zona fasciculata
Describe the appearance and staining of the adrenal medulla
Centre of the adrenal gland, with chromaffin cells- large, polyhedral
S100 +ve
What does the adrenal medulla secrete?
Adrenalin and noradrenalin
What cells are embryonic skeletal muscle cells derived from?
Myoblasts
What is a syncytium?
Multiple embryonic myoblasts fuse to form multi-celled syncytium
What is a myofibril?
Multiple sarcomeres joined end to end
What is the average diametre of a skeletal muscle fibre?
50-60 Micrometres
What is sarcoplasm?
Glycogen-rich cytoplasm in skeletal muscle
What is sarcolemma?
The cell membrane of a muscle cell
What is sarcoplasmic reticulum?
Endoplasmic reticulum in a muscle cell
Describe the histological appearance of skeletal muscle
Elongated fibres with striated cytoplasm. Cells are multinucleate with their nuclei at the edges of the cell, and the cells are non-branching
Why is striated muscle striated?
The myofibrils are in register!!!!!!!
Which section of a sarcomere is dark?
The a-band (myosin)
Which section of a sarcomere is light?
The i-band (actin)
What are type 1 skeletal muscles?
Slow twitch fibres, rich in fibrillar ATPase - derive energy from oxidative phosphorylation, fatigue resistant
What are type 2 skeletal muscles?
Fast twitch fibres, either derive energy from oxidative phosphorylation (Fatigue resistant), or glycolysis alone (fatiguable)
Where are type 1 skeletal muscles fibres found?
Muscles for posture (fatigue resistant)
Where are type 2 skeletal muscle fibres found?
Muscles for short bursts of power
What are muscle spindles formed of ?
Intrafusal muscle fibres wrapped around by gamma efferent nerve fibres, and encased in a fibrocollagenous capsule
What is the role of muscle spindles?
To detect stretch and tension
What are the three types of connective tissue in skeletal muscle?
Endomysium, perimysium, epimysium
What is the role of endomysium in skeletal muscle?
Holds together individual muscle fibres
What is the role of perimysium in skeletal muscle?
Binds groups of fibres to form fasicles
What is the role of epimysium in skeletal muscle?
Binds fasicles together
What are the roles of sharpey’s fibres?
Bind epimysium of muscle to periosteum of bone
What are sharpey’s fibres made of?
Bundles of collagen
Where are sharpey’s fibres found?
In areas where a large area of muscle and bone are connected
e.g. rotator cuff muscles to the scapula
Where are tendons found?
In areas where small areas of muscles and bone are connected
e.g. rotator cuff muscles to the humerus
What are tendons made of?
Parallel bundles of collagen with intervening fibroblasts
What are the four types of cells present in bone?
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
What is the extracellular matrix of the bone made of?
Collagen
Calcium hydroxyapatite
What cell type are osteoblasts and osteocytes derived from?
Osteoprogenitor cells (embryonic mesenchyme)
What do osteoblasts secrete?
Osteoid (unmineralised bone)
How do osteocytes connect to surrounding cells?
Canaliculi
What cell type are osteocytes derived from?
Monocytes
Describe the histological appearance of osteoclasts
Large, multinucleated bones, sitting on the bone surface
What are Howship’s lacunae?
Pits in the surface of bone which osteoclasts have absorbed
What is the structure of primary and secondary bone?
Primary- woven (haphazard osteoid)
Secondary- lamellar (parallel sheets of osteoid, forms osteons)
What are the two methods of bone formation?
Membranous
Endochondrial
What are the two different types of gross appearance of bone?
Spongy/cancellous
Compact
What is osteoid rich in?
Type I collagen
Glycosaminoglycans
Proteoglycans
Where is woven bone commonly found?
Growing bone and fracture sites
Is woven bone weak or strong?
Weak
What is a haversian canal?
The centre of an osteon, containing blood vessels
Which bones form via intramembranous ossification?
The flat bones of the skull and some cortical bone shafts
When does intramembranous ossification begin in utero?
The second trimester
What are the four layers that form during endochondrial ossification?
Resting cartilage
Zone of hyperplasia
Zone of hypertrophy
Zone of ossification
Where is synovium found?
Lining the inside of the joint capsule
How many layers of synovial cells are within a joint capsule?
1-4 layers
What is the difference between type A and type B synovial cells?
Type A- phagocytes
Type B- Rich in rER