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