Histology Flashcards
What five features are common to all eukaryotic cells?
- Outer membrane
- Inner cytosol
- Cytoskeleton
- Membrane bound organelles
- Structures within the cytoplasm which may or may not be bound by a membrane and these are called inclusions
What is a eukaryotic?
A cell with a true nucleus
What is the inner cytosol of a eukaryotic cell?
A solution of proteins, electrolytes and carbohydrates. It has both fluid and gel-like properties.
What is the cytoskeleton of a cell?
It determines the shape and fluidity of the cell. It is made from thin and intermediate filaments and microtubules.
What are inclusions?
Other structures in the cytoplasm which may or may not be bound by a membrane
What does the plasmalemma seperate?
The cytoplasm from the outside environment
How is the plasmalemma composed?
It is a bimolecular layer of amphipathic phospholipid molecules with their hydrophilic heads at the outer and inner surfaces and their hydrophobic fatty acid chains facing towards the middle of the 2 layers
Name five types proteins in the plasmalemma
- Receptors
- Channels
- Transporters
- Enzymes
- Cell attachment proteins
What is the cell membrane highly permeable to?
Water, oxygen, small hydrophobic molecules
What is the cell membrane impermeable to?
Charged ions (Na+)
Where is choline present in a phospholipid?
In the polar hydrophillic region (head)
Where is phosphate in a phospholipid present?
Below the choline in the polar, hydrophillic region (head)
What are small, intracellular ‘organs’ with a specific function nad structural organisation?
Organelles
Name 6 organelles in the cytoplasm
- Mitochondria (energy production)
- Rough endoplasmic reticulum (protein synthesis)
- Smooth endoplasmic reticulum (cholesterol and lipid synthesis/detoxification)
- Golgi apparatus (modification and packaging of secretions)
- Lysosomes (hydolytic enzymes for intracellular digestion)
- Nucleus (contains genetic code)
What do mitochondria do?
Energy production
What does the rough endoplasmic reticulum do?
Protein synthesis
What does the smooth endoplasmic reticulum do?
Cholesterol and lipid synthesis/detoxification
What does the Golgi apparatus do?
Modification and packaging of secretions
What do lysosomes do?
Hydrolytic enzymes for intracellular digestion
What does the nucleus contain?
Genetic code
What can inclusions only be present as?
Transients
What do inclusions represent?
Components that have been synthesised by the cell itself (pigment, glycogen stores, lipid droplets, presecretion product) or taken up from the extracellular environment (endocytotic vesicle)
What are the three main classes of filaments in the cytoskeleton?
- Microfilaments
- Intermediate filaments
- Microtubules
What are microfilaments composed of?
Protein actin
What are intermediate filaments composed of?
Six main proteins, which vary in different cell types
What are microtubules composed of?
Two tubulin proteins
What part of the cytoskeleton binds intracellular elements together and to the plasmallema?
Intermediate filaments
What two types of tubulin subunits are microtubules composed of?
Alpha and beta tubulin subunits
Where do microtubules originate from?
An organising centre called the centrosome
What filaments of the cytoskeleton contain stabilising proteins - MAPS?
Microtubule associated proteins - microtubules
Are microtubules polar or non-polar?
Polar - polymerise in the central portion of the cell and radiate outwards
What two proteins attach to microtubules and move along them?
Dynein and kinesin
What is kinesin and what direction does it move in?
ATPase and moves towards the cell periphery
What is dynein and what direction does it move in?
ATPase that moves towards the cell centre
What is the nucleus enclosed by?
A nuclear envelope
Describe the structure of the nuclear envelope
Composed of an inner and an outer nuclear membrane with nuclear pores providing continuity with the cytoplasm
What is between the two sheets of membrane in the nuclear envelope?
Perinuclear cistern
What is the perinuclear cistern continuous with?
The cistern of the endoplasmic reticulum
What is the outer nuclear membrane studded with?
Ribosomes
What is the outer nuclear membrane continuous with?
The cytoplasmic rough endoplasmic reticulum
Where does RNA synthesis occur?
In the nucleus
Where are mRNA and tRNA transcribed?
In the nucleus
Where is rRNA transcribed?
In the nucleolus
What two substances does the nucleus contain?
- Euchromatin
2. Heterochromatin
What is euchromatin?
DNA that is actively undergoing transcription
What is heterochromatin?
DNA that is condensed and not undergoing transcription
Where are ribosomes formed?
In the nucleolus
What is each ribosome made from?
A small subunit which binds to RNA and a large subunit which catalyses the formation of peptide bonds
What does reticulum mean?
Net-like structure
What does the endoplasmic reticulum do?
Forms a network of interconnecting membrane-bound compartments in the cell
What are the two types of endoplasmic reticulum?
Rough and smooth
What plays a vital role in the synthesis of proteins destined for insertion into membranes or for secretion?
The rough endoplasmic reticulum
What happens to proteins that are to remain unpackaged in the cytosol?
They are synthesised on polysomes floating free within the cytosol
What are the 4 steps involved in protein synthesis and the RER?
- Free ribosome attaches to mRNA
- If ER signal sequence is present, growing peptide is inserted into a pore in the ER
- Growing peptide forms in the ER; signal sequence removed
- Ribosome detaches. Most proteins then enter the SER
What is associated with the initiation of glycoprotein formation?
The Rough Endoplasmic Reticulum
What does the smooth endoplasmic reticulum continue doing?
the Processing of proteins produced in the RER
Where is the site of the synthesis of lipids?
SER
What is the Golgi apparatus compsed of?
A group of flattened, membrane bound cisternae arranged in sub-compartments
Where do transport vesicles arrive at the Golgi from?
The SER
What do Golgi cisterns function in?
The modification and packaging of macromolecules that were synthesised in the ER
What 3 things might the Golgi cistern do to macromolecules that were synthesised in the ER?
Add sugars
Cleave some proteins
Sort macromolecules into vesicles
What is special about the inner membrane of mitochondria?
It is extensively folded to form cristae which act to increase the availability of surface area
What do mitochondria function in the generation of?
ATP via oxidative phosphorylation and the synthesis of lipids and proteins
What are lipid droplets an example of?
An inclusion
What types of cells contain - sometimes 90% - of lipids?
Adipose cells
What are the 3 types of intercellular junctions?
- Occluding junctions
- Anchoring junctions
- Communicating junctions
What junctions link cells to form a diffusion barrier?
Occluding junctions
What junctions provide mechanical strength?
Anchoring junctions
What type of junction allows movement of molecules between cells?
Communicating junctions
What are two other terms for occluding junctions?
Tight junctions
Zonula occludens
What type of junction is an adherent junction?
Anchoring
What do adherent junctions do?
Link submembrane actin bundles of adjacent cells
What is another term for zonula adherens?
Adherent junctions
In adherent junctions: what do transmembrane cadherin molecules do?
Bind to each other in the extracellular space, and, through link molecules, to actin of the cytoskeleton
What type of junctions are desmosomes?
Anchoring junctions
What type of junction links submembrane intermediate filaments of adjacent cells?
Desmosomes
Where are desmosomes commonly found?
In the skin
What type of junction are hemidesmosomes?
Anchoring junctions
What junctions link submembrane intermediate filaments of a cell to the extracellular matrix through transmembrane proteins
Hemidesmosomes
What is a junctional complex?
Close association of several types of junctions found in cetain epithelial cells
What type of junction is often termed gap junctions?
Communicating junctions
What junctions are circular patches studded with several hundred pores?
Gap junctions or communicating junctions
What are pores produced by?
Connexon protiens
How can bacteria or larger particulate material from the extracellular space be incorporated into the cell?
By phagocytosis
What happens when a phagosome binds with a lysosome carrying digestive enzymes?
Produces a phagolysosome
Tissue is often fixed to preserve it in as life-like state as possible. Usually a chemical that cross-links proteins is used - give an example?
Formalin
What must impregnate tissues? (support material)
Usually wax
What is the most common combination of dyes?
Haematoxylin and Eosin (H&E)
What dye is basic, and has an affinity for acidic molecules and stains them purplish blue - for example the nucleus or ribosomes?
Haematoxylin
What dye is an acidic dye that has an affinity for basic molecules and staisn them pinkish red - such as proteins in the cytoplasm?
Eosin
What are the 4 basic tissue types?
Epithelium
Connective tissue
Muscle
Nervous tissue
What type of tissue: cover surfaces of the body or line hollow organs, and also form glands. They occur as sheets of cells and vary widely in size, shape, orientation and function.
Epithelium
What type of tissue: Forms the framework of the body, but beyond that it has a dynamic role in the development, growth and homeostasis of tissues, and, via fat, in energy storage
Connective tissue
What type of tissue: Specialised to generate force by contracting. There are three major kinds within the body.
Muscle
What type of tissue: Consists of neurons and their supporting cells. Serves a control function and allows for rapid communication between different parts of the body.
Nervous tissue
What do all epithelia have at their basal surface?
A layer of extracellular matrix components called a basal lamina (basement membrane), to which the cells are attached.
What are all epithelia?
Non-vascular - nutrients from capillaries in underlying tissue must diffuse across the basal lamina
Why are epithelila usually polarised?
Because the apical and basal ends of the cell differ
What type of cell shape is flattened, like a fish scale?
Squamous
What type of cell shape is cube shaped?
Cuboidal
What type of cell shape is like a column, relatively tall and thin?
Columnar
What does stratified mean?
Two or more layers
What does pseudostratified mean?
Tissue appears to have multiple layers but in fact all cells are in contact with the basal lamina
What three cell shapes can covering epithelia be classed into?
Squamous
Cuboidal
Columnar
What “number of layers”classification can covering epithelia be put into?
Simple
Stratified
Pseudostratified
In relation to covering epithelia: What 3 classes make up cell surface, or tissue surface, specialisations?
Prominent microvilli (termed brush border)
Cilia
Presence of layers of keratin protiens on the tissue surface (termed keratinised)
What are goblet cells?
Single cell mucous glands
What do glandular epithelia produce?
Secretory products such as sweat, milk, oil, hormones, mucous, enzymes and others
What are endocrine glands also termed?
Ductless glands
How is the product secreted in endocrine glands?
Product secreted towards the basal end of the cell (end sitting on basal lamina), then distributed by the vascular system throughout the body.
How is product secreted in exocrine glands?
Product secreted towards the apical end of the cell either into the lumen of an internal space, into a duct, or onto the body surface.
What are exocrine glands sometimes termed as?
Ducted glands
What 3 subtypes can connective tissue be subdivided into?
- Soft connective tissue
- Hard connective tissue
- Blood and lymph
What class of connective tissue do tendons, ligaments, mesentry, stroma of organs and dermis of the skin come under?
Soft connective tissue
What class of connective tissue do bone and cartilage come under?
Hard connective tissue
What two things are all connective tissue types composed of?
Extracellular matrix
Cells
What three things is the extracellular matrix in connective tissue made of?
- Fibres
- Ground substance
- Tissue fluid
Name three fibres that make up the extracellular matrix in connective tissue?
Collagen
Reticular
Elastic
What is an amorphous, space occupying material made of huge unbranched polysaccharide molecules called glycosaminoglycans (GAGs), most of which are bound to protein cores to form glycoproteins?
Ground substance
What do glycosaminoglycans (GAGs) produce when they bind with protein cores?
Glycoproteins
What are fibroblasts?
Widely distributed cells that produce and maintain the extracellular matrix
What are adipose cells and where are they found?
Fat cells, scattered in many connective tissues, but predominant cell in adipose tissue
What are osteocytes?
The cells of bone
What are chondrocytes?
The cells of cartilage
What two types of soft connective tissue are there?
Loose and dense
What type of tissue: loosely packed fibres seperated by abundant ground substance. Cells are relatively plentiful.
Loose soft connective tissue
What type of tissue: densely packed bundles of collagen fibres
Dense soft connective tissue
What is it called when dense soft connective tissue fibres are aligned (e.g. tendon)?
Dense regular CT
What is it called when dense soft connective tissue fibre bundles run in many directions (e.g. dermis of the skin)?
Dense irregular CT
Hard connective tissue - cartilage: what does the semi-rigid nature of the matrix come from?
The highly hydrated nature of the ground substance (GAGs and proteoglycans)
What is avascular and receives nutrients from adjacent tissues by diffusion through its matrix?
Cartilage
What are the three types of cartilage?
Hyaline
Elastic
Fibrocartilage
What is the type of cartilage defined by?
The extracellular matrix
Name 4 sites where hyaline cartilage is found?
Articular surfaces
Tracheal rings
Costal cartilage
Epiphyseal growth plates
An outer shell of dense what makes up the shaft of a bone?
Cortical bone - diaphysis
What type of bone occupies the ends of the bone (the epiphyses)?
Cancellous or trabecular bone
What is a fine meshwork of bone that looks a bit like the inside of an aero bar?
Cancellous bone
How is muscle force produced?
By the movement of actin fibres over myosin fibres, with the aid of accessory proteins
What are the 3 major types of muscle tissue?
Smooth
Skeletal
Cardiac
What type of muscle can also be called involuntary or visceral?
Smooth muscle
What type of muscle can also be called voluntary or striated?
Skeletal muscle
What type of muscle fibre is giant, multinucleated and cylindrical?
Skeletal muscle
Where are the nuclei of skeletal muscle cells located?
At the periphery of the cell, just internal to the cell membrane
What is the cell membrane called in muscle cells?
The sarcolemma
How many nuclei do cardiac muscle cells have?
One
In what type of muscle cell can intercalated discs be seen passing across the fibres at irregular intervals?
Cardiac muscle
What does nervous tissue consist of?
Neurons and support cells (glia)
What is the name of the connective tissue coat that surrounds nervous tissue in the central nervous system?
Meninges
What is the name of the connective tissue coat that surrounds the nervous tissue in the peripheral nervous system?
Epineurium
What are the three types of principal glia of the CNS?
Astrocytes
Oligodendrocytes
Microglia
What do astrocytes do?
Support and ion transport
What do oligodenrocytes do?
Produce myelin
What do microglia do?
Provide immune surveillance
What are the principal glia of the PNS?
Schwann cells
What do Schwann cells do?
Produce myelin and support axons
What are the 3 major salivary glands?
Parotid
Sublingual
Submandibular
What type of cell stains intensively?
Serous secreting cells
What type of secreting cells are the parotid gland cells?
Serous secreting cells
What type of secreting cells are the submandibular glands?
Mucous secreting
Name one unusual feature of salivary glands?
The striated ducts
Name the feature that modifys the saliva that is passing through by pumping salt out of the fluid so that it is hypotonic to blood.
Striated ducts
What are the 4 major layers that compose the digestive tract (starting from the lumen and going out)?
Mucosa - 3 parts
Submucosa
Muscularis Externa
Serosa or Adventitia
What three parts make up the mucosa in the digestive tract?
Epithelium - sits on basal lamina
Lamina propria - loose connective tissue
Muscularis Mucosae - thin layer of smooth muscle
What is the muscularis externa of the digestive tract?
Two thick layers of smooth muscle, an inner circular layer and an outer longitudinal layer
What is the serosa or adventitia of the digestive tract?
Outer layer of connective tissue that either suspends the digestive tract or attaches to other organs
Where is protective mucosa found?
Oral cavity, pharynx, oesophagus and anal canal
Where is absorptive mucosa found?
In the small intestine
Where is secretory mucosa found?
In the stomach
Where is protective and absorptive mucosa found?
In the large intestine
What type of mucosa is non-keratinised stratified squamous epithelium?
Protective
What type of mucosa is simple, columnar epithelium with villi & tubular glands?
Absorptive
What type of mucosa is simple columnar epithelium with extensive tubular glands?
Secretory
What type of mucosa is simple columnar epithelium with tubular glands?
Protective and Absorptive
In the large intestine, outer longitudinal smooth muscle is not continuous - how is it found?
In 3 muscular strips called teniae coli
What is the digestive tracts own nervous system called?
The enteric nervous system
Where do most of the neurons in the enteric nervous system live?
In groups called ganglia between the two muscle layers that make up the muscularis externa
Name the 4 layers of the trachea - starting from the airway
Airway Respiratory epithelium Lamina propria Seromucous gland in the submucosa Hyaline cartilage of tracheal ring
What produces a viscous fluid that coats the surface of the airway and traps particles that are then propelled out of the airway by cilia?
The goblet cells of the epithelium and the submucosal glands
Which is larger in diameter - bronchi or bronchioles?
Bronchi
Which has hyaline cartilage in their walls - bronchi or bronchioles?
Bronchi
The further down the respiratory tree you go - what happens to the columnar cells of the epithelium?
They tend to get shorter
What are alveoli lined with?
Squamous epithelium
What structures with hexagonal arrangements make up the liver?
Lobules
What is there in each corner of a lobule?
A branch of the hepatic portal vein and a branch of the hepatic artery, each delivering blood to the lobule
What is present in the centre of lobules?
A central vein which drains to the hepatic vein
What are liver cells called?
Hepatocytes
What are the spaces for blood flow in the liver lobules called?
Sinusoids
What does the exocrine pancreas produce?
Digestive juices containing proteases, lipases and nucleases
What do proteases do?
Break down proteins
What do lipases do?
Breakdonw lipids
What do nucleases do?
Break down DNA/RNA
Where do digestive juices from the exocrine pancreas enter the duodenum?
Via the pancreatic duct
What does the endocrine pancreas consist of?
Scattered Islands of tissue called Islets of Langerhans
What do Islets of Langerhans in the endocrine pancreas produce?
Hormones including insulin
What is the renal corpuscle?
A tuft of capillaries surrounded by epithelium - the production of urine begins here
What is the kidney composed of thousands of?
Nephrons
What is another term for red blood cells?
Erythrocytes
What is another term for white blood cells?
Leukocytes
What do red blood cells lack?
A nucleus
What are the 5 principal types of white blood cells?
- Neutrophils
- Eosinophils
- Basophils
- Monocytes
- Lymphocytes
What are neutrophils, eosinophils and basophils collectively termed?
Granulocytes
What are the 3 layers of a muscular artery? (From the middle of the lumen)
Tunica Intima - which extends to an internal elastic membrane
Tunica media
Tunica Adventitia
What seperates the tunica media and tunica adventitia?
The external elastic membrane
What is the simple squamous epithelium of blood vessels referred to as?
Endothelium
What are capillaries essentially composed of?
Endothelial cells and a basal lamina
What is excess tissue fluid called?
Lymph
What are lymph vessel walls made of?
Smooth muscle
How is flow produced in lymph vessels as there is no pump?
Smooth muscle in walls, hydrostatic pressure in the tissue and compression of the vessels by voluntary muscle, combined with the valves in the vessels produce flow
What is the tunica intima?
A single layer of squamous epithelial cells termed endothelial cells supported by a basal lamina and a thin layer of connective tissue
Inner layer
What is the tunica media?
Made up of predominately smooth muscle. Thickness of this layer varies.
Middle layer
What is the tunica adventitia?
Made up of supporting connective tissue
Outer layer
What layer of blood vessel is closest to the lumen?
Tunica intima
Name an elastic artery?
Aorta
Why are large arteries termed elastic arteries?
Because they have many sheets of elastic fibres in their tunica media to provide elastic recoil
What stains elastic fibres black, collagen fibres green and smooth muscle cells red?
Verhoeff’s/Masson trichrome stain
In elastic arteries (large arteries) what half of the wall can obtain nutrients from the lumen?
The inner half
What is the vascular supply of elastic arteries/large arteries called?
Vasa vasorum
What stains collagen red, cytoplasm yellow and elastin black?
Modified van Gieson’s stain
What extends to an internal elastic lamina?
Tunica intima
What extends to an external elastic lamina?
Tunica media
What oftens has pericytes at intervals just outside the basal lamina?
Capillaries
What are pericytes?
Connective tissue cells that have contractile properties
What are the 3 types of capillaries?
Continous - muscle, nerve, lung, skin
Fenestrated - gut mucosa, endocrine glands, kindey
Sinusoidal - liver, spleen, bone marrow
What do fenestrated capillaries have?
Small pores
Where do capillary networks drain into?
Post-capillary venules
What are endothelial cell lined and associated with pericytes?
Post-capillary venules
Once a post-capillary venule begins to aquire intermittent smooth muscle cells in a tunica media layer - what are they referred to as?
Venules
What do most small and medium sized veins have that are inward extensions of the tunica intima?
Valves
Where is the most blood present in the body?
Peripheral veins
How can blood be seperated?
Spinning in a centrifuge
What is found (from bottom to top) in a test tube of blood that has been spun in a centrofuge?
Red cells, white cells, plasma
If clotting factors are removed from the blood, what is the remaining liquid termed?
Serum
What is the diameter of erythrocytes (red blood cells)?
7 nano metres
How long do erythrocytes last in circulation?
4 months
What 2 organs remove aged red blood cells?
Liver and spleen
What is a rouleau?
Red blood cells found in stacks
What shape do red blood cells have?
Biconcave
What is the most common type of leukocyte?
Neutrophils
Which leukocyte has many granules in their cytoplasm, stains poorly with acidic or basic dyes and has a prominent, multilobed nucleus?
Neutrophils
What state do neutrophils circulate the blood in?
Inactive state
What do neutrophils turn into when activated by bacteria or inflammation and entering tissues?
Phagocytes
What leukocytes have a bilobed nuecleus and granules containing a variety of hydrolytic enzymes?
Eosinophils
What leukocytes are important in allergic reactions and gihting parasitic infection?
Eosinophils
What do the prominent granules in the cytoplasm of eosinophils have an affinity for?
Red acidic dye eosin
What are the rarest granulocytes?
Basophils
What do the prominent granules in basophils cytoplasms have an affinity for?
Basic dyes such as methylene blue
What type of nucleus do basophils have?
Bilobed nucleus
What substances do basophil granules contian?
Histamine, heparin and other inflammatory mediators
What type of granulocyte acts as effector cells in allergic reactions?
Basophils
What do basophils have present in their cell membrane that are directed against particular allergens?
High affinity IgE receptors
What serves as precursors of tissue macrophages?
Monocytes
Where are macrophages particularly found in?
Loose connective tissue
What leukocytes have numerous small lysosomal granules in their cytoplasm, are the largest cells circulating in the blood and have a non-lobulated nucleus which often appears kidney bean shaped?
Monocytes
What is the name for monocyte/macrophage cells that remain resident in the liver?
Kupffer cells
What is the name for monocytes/macrophages that are resident in the brain?
Microglia
What is the name for monocytes/macrophages that are resident in the skin?
Langerhan’s cells
What leukocytes have a round nucleus surrounded by a thin to moderate rim of cytoplasm that does not have visible granules?
Lymphocytes
What are the two general classes of lymphocytes?
T cells and B cells
Where do lymphocytes arise in?
The bone marrow
Where do T cells differentiate?
In the thymus
What do B cells give rise to?
Antibody secreting plasma cells
What part of platelets participates in extrusion of granules and in clot retraction?
Cytoskeleton
Do platelets have a nucleus?
No
What three things do platelets do in the process of hemostasis?
Adhere
Aggregate
Degranulate
During the second trimester - where is the prinicpal site of blood formation?
In the liver
By birth - where is the principal site of blood formation?
Bone marrow
What do erythrocytes develop in the bone marrow from?
Stem cells
When is a cell termed a reticulocyte?
When it has granules of RNA in their cytoplasm - occurs in erythrocyte development
What is the name of giant cells found in the bone marrow?
Megakaryocytes
What are formed from megakaryocytes?
Platelets
