Histology Flashcards
What does alcian blue stain?
GAG-rich structures
Mucous goblet cells
Mast cell granules
Cartilage matrix
What does Perl’s stain do?
Stains ferric iron a Prussian blue colour.
Give two places where you would find stratified squamous non-keratinising epithelium:
- Mouth
2. Vagina
What can be used to stain basement membranes?
Periodic acid shiff (PAS).
What is contact inhibition?
When epithelial cells will grow until they are in contact with their neighbours where they will then stop.
What help to spread mechanical forces across a tissue?
Desmosomes that join the cytoskeletons of adjacent cells.
What are connective tissue cells mainly derived from?
Pluripotent undifferentiated mesenchymal cells.
Name the three main types of connective tissue:
- Fibrous
- Hard
- Fatty
What do fibroblasts secrete?
Collagen - in the form of tropocollagen subunits.
What is ground substance?
An amorphous gel-like substance which contains mainly glycosaminoglycans (GAGS) which link together to form proteoglycans. It also contains some invisible fibres such as laminin and fibronectin.
What is another name for type III collagen?
Reticulin
Where is reticulin found?
Liver, bone marrow, lymph node, spleen and Peyer’s patches.
What colour will extracellular fibres stain?
Pink, due to eosin.
What stain do we have to use for Reticulin and why?
Silver stain, because it does not show up on H + E.
What produces elastic fibres?
Fibroblasts.
What is the difference between white and brown adipocytes?
White adipocytes have one large fat globule whereas brown adipocytes have many smaller globules.
What do white adipocytes sometimes get confused with on a histological slide?
Lung cells.
- as the fat globule is usually lost during processing, leaving a large white space.
Why is brown adipose tissue important in neonates?
It is used in thermoregulation as heat is produced on its breakdown.
(Found on the backs and shoulders of children and shrinks as you age)
What are the three types of cartilage?
Hyaline, elastic and fibrocartilage.
What do chondrocytes (blasts if immature) produce?
The major extra cellular component of cartilage.
What type of cartilage is found in synovial joints and what are some of it’s features?
Hyaline Cartilage.
- Blueish grey matrix with chondrocytes entrapped within it.
- glassy appearance with no visible fibres.
- perichondrium on the outside, which is comprised of fibroblasts and extracellular collagen fibres.
What is found in the annulus fibrosus and what are it’s features?
Fibrocartilage.
- matrix rich in visible collagen fibres and bas entrapped chondrocytes.
- has a perichondrium.
What type of cartilage is in the epiglottis and what are it’s features?
Elastic cartilage.
- Blue/grey with entrapped chondrocytes.
- Elastic fibre in the matrix that stain.
What are the two types of synovial cell?
Type A - Phagocytes.
Type B - Rich in RER and secrete synovial fluid.
Make up the 4 layers of the synovium which is a high vascularised and innervated tissue.
What are the layers of an artery from the inside to the out?
Lumen -> endothelium -> basement membrane -> Intima -> internal elastic lamina -> media -> external elastic lamina -> adventitia.
When is the vessel defined as an arteriole and not an artery?
- When is has 3 or fewer layers of muscle in the media.
And/Or - It has a diameter of 100um or smaller.
What are pericytes and where are they found in the body?
They are contractile cells that are present in capillaries and venules - in the smallest vessels they form an incomplete ring. They are replaced by smooth muscle in veins.
What is missing from the walls of a vein?
Elastic lamina.
What are the characteristics of a lymph vessel?
- Thin layers of intima, media and adventitia.
- Contains valves like veins.
- Carries lymph not blood.
What are the layers of connective tissue in nerves?
- Endoneurium - binds individual axons together.
- Perineurium - surrounds groups of axons to form fascicles.
- Epineurium - binds fascicles together to form nerve fibres.
What colour does silver stain (golgi’s method) stain neuronal tissue?
Dark brown/black.
Are schwann cells present with unmyelinated axons?
Yes - they are just not wrapped round. The may be more than one unmyelinated axon per schwann cell.
Where are the cell bodies of lower motor neurons found?
The anterior part of the spinal grey matter (usually ventral horn).
Where are the cell bodies of sensory neurons found?
In the dorsal root ganglion, just before the spinal chord.
What are the four layers of the heart? (from inside to out)
Endocardium, Myocardium, Epicardium, Pericardium.
What are the three layers of the pericardium? (From outside to in)
- Fibrous pericardium.
- Parietal pericardium.
- Visceral pericardium (epicardium)
Why is the Heart regarded as an endocrine organ?
Myocytes of the atria have perinuclear neuroendocrine granules containing atrial natriuretic peptide.
Why do purkinje fibres stain white on H + E?
Because they have a glycogen rich cytoplasm.
What are the percentages of the different constituents of the blood?
Plasma (56%)
Erythrocytes (43%)
Leukocytes (1%)
What is serum?
Plasma WITHOUT clotting factors.
What is the lifespan of an erythrocyte?
Approximately 120 days.
What is the lifespan of a platelet?
8 to 9 days in circulation.
What maintains the cell shape of an erythrocyte?
The endoskeleton that is attached to a protein called spectrin.
What are the most common type of leukocyte?
Neutrophils.
How do neutrophils destroy bacteria?
By engulfing them and releasing reactive oxygen species (respiratory/oxidative burst).
What enzyme helps with the initiation of respiratory burst?
Myeloperoxidase.
When do eosinophil numbers increase? What are some of it’s features?
Usually 1%, but increase in parasitic infections.
- Bi-lobed nucleus.
- Large red cytoplasmic granules.
- ‘Lozenge’ shaped granules with crystalline inclusions.
- Antagonistic to basophils and inhibit mast cell secretion.
- Neutralise histamine.
What is the appearance and features of Basophils?
- (0.5% of leukocytes in the blood)
- Bi-lobed nucleus which is hard to see due to dark staining blue cytoplasmic granules.
- Granules contain histamine.
- Receptors for IgE.
What are the two main divisions of leukocytes?
Granulocytes and Agranulocytes.
What are the 5 main types of T lymphocyte?
- Helper
- Cytotoxic
- Memory
- Regulatory
- Natural killer
How do you differentiate between lymphocytes by looking at them?
You can’t, they all look the same.
What do B lymphocytes do?
They become plasma cells that secrete antibodies.
What are monocytes?
A type of immature leukocyte, that briefly (a couple of hours) circulate within the blood with a reniform (kidney bean) nucleus that can differentiate into several kinds of cell once in tissue.
Do monocytes contain granules?
Yes, although they are classed as agranulocytes, they contain small granules.
What do monocytes differentiate into?
- Tissue macrophages - everywhere.
- Kupfer cells - liver.
- Osteoclasts - bone.
- Antigen presenting cells - everywhere.
- Alveolar macrophages - lungs.
What cell is described to have a ‘clock face’ nucleus?
Plasma cells.
- The nucleus is off to one side of the cell, leaving a perinuclear hof.
What is hematopoiesis and what is the starting cell?
The formation of blood cells from stem cells, stemming from a hemocytoblast (a multipotential hematopoietic stem cell).
What type of epithelium is respiratory epithelium?
Pseudostratified columnar ciliated epithelium with interspersed goblet cells.
What are 4 functions of the nasal cavity?
- Filtration.
- Humidification.
- Warming.
4 Olfaction.
Which areas does olfactory epithelium line?
Olfactory epithelium lines the roof of the nasal cavities, part of the nasal septum, and the superior turbinate (concha) bones.
What type of epithelium is olfactory epithelium?
Pseudostratified columnar ciliated epithelium - the cilia are stereo cilia (non-moving).
It has penetrating nerve fibres that reach the surface and serous gland of bowman that are below the surface that secrete a watery substance that keeps the surface clean.
Describe the innervation to olfactory epithelium:
Olfactory receptor cells and bi-polar neurons that have their dendrites extend to the surface to become club-shaped ciliated olfactory vesicles.
What are nasal sinuses and what are their function?
Air filled spaces in the skull that lower the weight of the skull, as well as adding resonance to the voice. They also humidify and warm inspired air. These sinuses are lined by respiratory epithelium.
What type of cartilage makes up the larynx?
Hyaline cartilage.
What epithelium lines the vocal chords?
Stratified squamous non-keratinising epithelium
What is Reinke’s space?
A gelatinous layer underneath the outer cells of the vocal chord that is important in their vibration.
What is the order of the bronchial tree from largest to smallest?
Main (primary) bronchi-> lobar (secondary) bronchi ->segmental (tertiary) bronchi -> bronchioles (lobular + terminal + respiratory).
What type of epithelium is bronchioles? And what other cells are there?
Cuboidal ciliated epithelium with a few goblet cells and some cells called Clara cells.
What are Clara (club) cells?
- Most numerous in the terminal bronchioles, they are cuboidal and have no cilia, have lots of of mitochondria and smooth er.
- They are thought to secrete a lipoprotein that stops the collapsing of the airway in exhalation.
What is the first part of the distal respiratory tract?
The respiratory bronchioles - they have a role in gaseous exchange as well as transport.
How many alveoli are there per lung? And what is the diameter of one alveolus?
150-400 million and 250 um
What percentage do type 1 pneumocytes make up in
a: surface area
b: cell population
of the alveoli?
90% surface area.
40% cell population.
How are alveolar macrophages removed after completing their function?
By entering the lymphatic system or via the mucocillary elevator.
Which mucosa of the stomach has parietal cells and what do these cells do?
Body mucosa and they secrete hydrochloride acid and intrinsic factor.
What are the pacemaker cells of the gastrointestinal tract and what layer are they found in?
The interstitial cells of cajal and in the muscular propria.
Where are water soluble vitamins absorbed?
The Jejunum (except b12).
What is the whole gut covered in?
Mesothelium.
How does the stomach regenerate itself?
From stem cells that come from the intestinal crypts.
How does the small intestine increase surface area?
Plicae circulares and villi with microvilli on them.
What are the two models that can be used to show organisation within the liver?
- The lobule, based on drainage.
Or: - The acinus, based on blood supply.
Which hepatocytes will receive more nutrients and why is this of clinical relevance?
The ones closest to the hepatic arteries and portal veins, and the cells can be used to infer the location of the vessels.
What type of cell is a hepatocyte?
Polyhedral epithelial cell.
What are the three surfaces of a hepatocytes and what percentage do each one of these make up of the total surface?
- Sinusoidal (70%).
- Canalicular (15%).
- Intercellular (15%).
What is another term used to describe the perisinusoidal space?
Space of Disse.
What is another term for hepatic stellate cells and what to they do?
Ito cells - the major storage site for vitamin A, fat storage and a source of stem cells.
True or false, sinusoids have a fenestrated basement membrane.
False - sinusoids have NO basement membrane.
What type of epithelium makes up the gallbladder?
Simple columnar epithelium, with microvilli.
What are the layers of the gallbladder wall?
Epithelium, basement membrane, loose fibrous mucosa, smooth muscle, another layer of loose fibrous connective tissue.
What is the function of the exocrine pancreas?
To synthesise and secrete enzymes and bicarbonate rich fluid into the duodenum.
Describe the acinar cells of the pancreas? (3 points)
- Pyramidal in shape.
- Rich in RER basaly.
- Apically (opposite base) there are zymogen granules which contain enzyme precursors.
What structures do we usually find in the renal cortex? (3)
Glomeruli, proximal convoluted tubules and distal convoluted tubules.
What structures of the nephron are found in the renal medulla? (2)
The loops of Henle and the collecting ducts.
What three things make up the glomerular filter?
The fenestrated endothelium of the capillaries, the glomerular basement membrane and the foot processes of podocytes.
What do mesangial cells do?
Remove trapped residue and aggregated protein from the basement membrane to keep is free of debris.
They also provide structural support.
Describe the basement membrane of the glomerulus:
Double layered with collagen and negatively charged heparin sulphate molecules.
What forms the juxtaglomerular apparatus and what is it’s function?
Formed from the distal convoluted tubule and the glomerular afferent arteriole.
- It’s main functions are to regulate blood pressure and filtration rate of the glomerulus. (THINK RENIN)
Describe the epithelium of proximal convoluted tubule.
Cuboidal epithelium with a brush border of microvilli at the apical end. Cells contain mainly mitochondria.
What type of cells make up the different parts of the loop of henle?
Thick - low cuboidal.
Thin - simple squamous.
Which part of the kidney regulates acid/base levels and how?
The distal convoluted tubule and the collecting duct - by secreting H+ and absorbing HCO3- via cellular carbonic anhydrase.
How does the distal convoluted tubule regulate Na+ levels?
By exchanging urinary sodium for body potassium.
What enzyme is involved with the regulation of sodium?
Aldosterone.
Mutation of what gene causes hereditary diabetes insipidus?
The gene for aquaporin 2.
What cells in the collecting duct help to maintain body pH?
Alpha intercalated cells secrete H+ and Beta intercalated cells secrete HCO3-. Can’t differentiate on H and E stains.
What does the Renal artery split into?
The segmental arteries.
Why is the loop of Henle prone to ischemia?
Because the vasa recta is far from the glomerulus.
What type of epithelium lies the renal pelvis?
Urothelium - a complex stratified epithelium. A layer of umbrellas cells overlying a pseudo-stratifiedlayer of cells.
What is the formation of the muscular tube of the ureters?
Spiral muscular tube with longitudinal muscle in the inner and circular on the outside - opposite to the GI tract.
What stops reflux of urine back into the ureters?
A functional valve created by the muscular propria of the bladder wall.
Are male and female urethra’s the same?
No, men’s are longer (20 vs 5cm) and more complex, consisting of 3 parts (prostatic, membranous and penile urethras) vs two parts in the female (transitional and squamous).
Which urethra has glands the secrete into it?
The female urethra.
What directly gives rise to the afferent arterioles in the kidney?
Interlobular arteries.
What types of filaments make up the cytoskeleton? (3)
Microfilaments (5nm actin) + Intermediate filaments (10nm + 6 types) + Microtubules (25nm Tubulin).
Why are intermediate filaments important in histology?
Because different types of cells have different intermediate filament proteins, so they can be used to identify different cells (e.g. desmin is in myocytes whereas cytokeratins are in epithelial cells).
