Microanatomy Flashcards
(134 cards)
1
Q
What are the three layers of connective tissue that hold muscle fibres in position in skeletal muscle?
A
- Epimysium - outermost layer surrounding the entire muscle.
- Perimysium - surrounds bundles of muscle fibres to create a fascicle.
- Endomysium - surrounds each individual muscle fibre within the fasciculus.
2
Q
What are tendons made of?
A
Collagen fibres.
3
Q
Why are skeletal muscle fibres multinucleated?
A
Because lots of muscle cells fuse together during devlopment forming a myotube.
4
Q
What do satellite cells become when they are stimulated to leave their normally quiescent state? When does this happen?
A
They become myoblasts which then proliferate and differentiate to provide new myonuclei.
This happens during:
- Growth after birth.
- Muscle hypertrophy.
- Muscle maintenance.
- Muscle repair and regeneration.
5
Q
What causes skeletal muscle to have a striated appearance?
A
The organisation of thick and thin filaments and divisions into sarcomeres.
6
Q
What are thick and thin filaments composed of?
A
- Thick = myosin.
- Thin = actin.
7
Q
What makes the: A band, I band, H band and Z lines.
A
- A band = the dark stripes of the sarcomere (myosin filaments).
- I band = light region of the sarcomere (actin filaments).
- H band = the portion of the myosin filament where there is no overlap with actin.
- Z lines = the end of the sarcomere is depicted by these lines.
8
Q
What are the functions of the T-tubules and sarcoplasmic reticulum?
A
T-tubules conduct impulses from the surface of the cell down to the sarcoplasmic reticulum which in turn provides calcium for contraction.
9
Q
How are cardiac myocytes connected?
A
They are connected via intercalated disks (which are modified Z-lines) to form a functional syncytium.
10
Q
Are the fibres straight or branching in cardiocytes?
A
Branching
11
Q
How are smooth visceral muscles fibres often arranged?
A
In layers with alternating longitudinal and transversely orientated layers of cells.
12
Q
Why is there a small amount of connective tissue between smooth muscle cells?
A
Allow for passage of nerve tracts and blood vessels.
13
Q
How are smooth muscle myofilaments arranged?
A
The myofilaments are loosely organised and attached to focal densities in cytoplasm and focal adhesion densities (attachment plaques) at the cell membrane.
14
Q
What is appositional and interstitial growth?
A
- Appositional = where the fibroblasts in perichondrium give rise to chondrocytes.
- Interstitial = where chondrocytes in matrix proliferate.
15
Q
What are the two main components of cartilage and what do they provide?
A
- Collagen II (60%) - gives tensile strength.
- GAGs (chondroitin sulphate, 40%). These couple to proteins to form enormous proteoglycans. They are hydrated and give resistance to compression. Electro-osmotic.
16
Q
What is the cartilage matrix made up of?
A
Chondrin
17
Q
What are the inorganic and organic compositions of bone?
A
- Inorganic = mainly hydroxyapatite found in needle-like crystals or thin plates that are 8nm thick and variable in length.
- Organic = 90% type I collagen. Remaining 10% is other proteins.
18
Q
What is the only way that bone can grow?
A
Appositional growth.
19
Q
What is the outer layer of bone called?
A
Cortical (compact) bone.
20
Q
What is the interior of bone called and what are the internal surfaces lined with?
A
Trabecular (cancellous, spongy) bone.
Lined with endosteum.
21
Q
What are the articular and non-articular surfaces of bone lined with?
A
- Articular surfaces are covered with articular cartilage (hyaline).
- Non-articular surfaces are covered with periosteum.
22
Q
What is the epiphyses and diaphysis and what is found inbetween them?
A
- Epiphyses = expanding end of bone.
- Diaphysis = shaft of bone connected to the epiphyses.
- Between is the growth plate and the transition zone called the metaphysis.
23
Q
What are Haversian systems comprised of and what connects them transversely?
A
- 4-20 concentric lamellae surrounded by a cement line (1µm) of mineralized matrix.
- Connected by Volkmann’s canals.
24
Q
What are lamellae?
A
Collagen laid down in sheets, 5µm thick. They alternate orientation between sheets to give greater strength.
25
What are the two major patterns that lamellae are arranged in?
1. Circumferential = layers surrounding the bony surface.
| 2. Haversian systems (osteons).
26
What are osteoprogenitor cells and where are they found?
- Mesenchymal, fibroblast-like stem cells that generate osteoblasts.
- In cancellous (spongy) bone, found
near blood vessels.
- In compact bone, found at
periosteum and endosteum.
27
Where are osteoblasts found and what are they responsible for?
- Found on the surface of bone.
| - Responsible for deposition of osteoid (the organic component of bone matrix) and inducing mineralisation.
28
What are canaliculi and why are they important?
They are canals that radiate from the lacunae and contain osteocyte cell processes.
They permit diffusion of substances through the bone.
29
What are the possible functions of osteocytes?
- Role in Ca homeostasis.
- Responsive to mechanical forces.
- Mediate mechanically adaptive bone remodeling by acting as strain receptors.
30
What are bone-lining cells?
Undifferentiated, flattened cells that are found on the surface of bone that is not being remodelled. They may represent inactive osteoblasts.
31
What are osteoclasts and where are they found?
They are variably sized cells that are involved in the reabsorption of bone which contributes to bone remodelling and Ca homeostasis.
Found in resorption cavities (Howship's lacunae) on the bone surface.
32
What are osteoclasts directly inhibited by?
Calcitonin
33
How are Haversian systems formed?
By osteoclasts tunneling through pre-existing bone and the tunnels being invaded by blood vessels and osteoprogenitor cells.
The osteoblasts then lay down successive bone lamellae on the walls of the tunnel.
34
What are the five phases of digestion?
1) Ingestion
2) Fragmentation
3) Digestion
4) Absorption
5) Elimination
35
What are the three layers of the gut mucosa?
1) Specialised surface epithelium are found resting on the basal lamina.
2) Lamina propria consists of loose connective tissue with blood and lymph vessels as well as nerve fibres and smooth muscle.
3) Muscularis mucosae is a thin double layer of smooth muscle.
36
What does the submucosa of the gut consist of?
Loose connective tissue with:
- Blood vessels
- Nerves which form plexuses
- Leukocytes
- Lipids
37
What is the adventitia/serosa of the gut?
A thin layer of connective tissue continuous with surrounding organs. It is bound by a simple squamous epithelium termed mesothelium.
38
What are the two layers of the muscularis externa?
1) Inner circular layer
| 2) Outer longitudinal layer
39
What epithelium is found in the oesophagus and what is its function?
Stratified squamous epithelium. There for physical protection as well as keeping the area moist by glandular secretions.
40
How can you identify the oesophagus on a histological image?
- Stratified squamous non-keratinising epithelium in the mucosa.
- Groups of mucous glands in the submucosa.
41
What epithelia make up the mucosa in the stomach?
Simple columnar epithelial layer of mucous secreting cells invaginating to form gastric pits that produce acid and enzymes.
42
What is the function of surface mucous cells in the stomach?
They secrete mucous and bicarbonate to protect cells from acidic and enzymatic properties of gastric juices and ingested food.
43
What is the function of mucous neck cells and where are they found?
They line the upper parts of the gastric pits and secrete mucous.
44
How would you recognise chief cells and parietal (oxyntic) cells on a histological slide?
- Chief cells have a condensed, basically located nucleus and a basophilic cytoplasm with granules.
- Parietal (oxyntic) cells are large, rounded cells with eosinophilic cytoplasm and a centrally located nucleus (fried egg appearance).
45
What is the difference in the stomach mucosa between the cardia, body and pylorus?
- Cardia has sparse glands and mainly mucous secreting cells.
- Body has densely packed glands which produce gastric juices.
- Pylorus has deep pits which are branching and coiled. Nearly all of the cells here are mucous-secreting cells.
46
What epithelium is found within the small intestine?
Simple columnar with a brush border of microvilli to increase the surface areas for absorption.
47
What are villi composed of?
Their surface layer is made up of entrocytes and goblet cells sitting on a basal lamina with a core of lamina propria consisting of loose connective tissue with blood and lymph vessels, nerve fibres and smooth muscle.
48
What are lacteals?
Lymphatic vessels found in villi of the small intestine that take away fats in chylomicrons.
49
What is the structure of a microvillus?
Its shape is maintained by actin filaments which are anchored to the cell membrane. The base of the actin filaments form part of the terminal web which is linked to the intermediate filaments of the cell.
50
What is the function of paneth cells and where are they found?
They release digestive enzymes, immunoglobulins and lysozymes which help destroy parasites and bacteria. They are found in the lower 3rd of the crypts in the small intestine mucosa.
51
What is the role of the hormones endocrine cells secrete in small intestine?
- Regulate water and electrolyte metabolism and enzyme secretion.
- Regulate gastrointestinal motility and mucosal growth.
- Stimulates the release of other hormones.
52
What are submucosal Brunner glands?
They are glands found in the small intestine who's main role is to aid in neutralising the acid chyme extruded from the pylorus.
53
How does the jujenum differ from the duodenum?
The jujenum has the tallest villi, no Brunner's glands and few lymphoid follicles.
54
What feature of a histological slide of ileum makes it easily identifiable?
It has very large aggregations of lympoid tissue called Peyer's patches.
55
What structures mucosa resembles the colon? What is the difference?
Appendix - is heavily infiltrated with lymphocytes.
56
What cells are found in the mucosa of the colon?
There are no villi. Columnar epithelia make up the surface with large quantities of goblet cells.
57
What cell types make the epithelium of the tubular glands of the colon?
1) Enterocytes with microvilli.
| 2) Goblet cells.
58
What happens to the epithelium at the ano-rectal junction?
There is an abrupt transition from simple columnar to stratified squamous epithelium. There is also the presence of branched, tubular glands which secrete mucus onto the anal surface.
59
What are the apocrine circumanal glands?
They are sweat glands that open on to the skin around the anal orifice.
60
What does saliva contain?
- Mucus
- Enzymes (mainly amylase)
- Anti-bacterial enzymes
- Proteins
- Antibodies
- Inorganic ions
- Proteins that coat teeth for protection
61
Describe the parotid gland.
It is a major salivary gland make of almost exclusively serous cells producing a thin watery secretion rich in enzymes and antibodies.
62
Describe the sublingual gland.
It is a major salivary gland made of predominantly mucous cells which produce a viscid (sticky) secretion.
63
Describe submandibular glands.
They are major salivary glands that contain both serous and mucous secretory cells.
64
What are the minor accessory salivary glands?
- Buccal
- Labial
- Lingual
- Palatine
65
What are the differences between serous acinar cells and mucous acinar cells?
- Serous has lots of RER and secretory granules.
| - Mucous has an irregularly shaped basally located nucleus, lots of golgi and lots of mucous product in the cytosol.
66
What are serous demilunes?
They are cellular formations in the shape of a half-moon on some salivary glands. They secrete proteins that contain the enzyme lysozyme which is used to break down cell walls.
67
What cells line intercalated ducts of salivary glands?
Cuboidal epithelium.
68
Describe the epithelium that line the striated duct of the salivary gland.
They are tall columnar epithelium characterised by interdigitations of cytoplasmic processes and columns of mitochondria in the basal cytoplasm. They modify saliva from isotonic to hypotonic by replacing Na and Cl with K and HCO3-.
69
What epithelium line the interlobular and lobular ducts of the salivary gland?
- Interlobular = psuedostratified columnar epithelium.
| - Lobular = columnar stratified epithelium.
70
What are the different parts of a salivary gland?
From inside out:
- Acinus
- Intercalated duct
- Striated duct
- Intralobular duct
- Interlobular duct
- Lobular duct
- Main duct
71
How do you identify Islets of Langerhans on a histological slide?
They are large patches of white cells scattered within pancreatic tissue.
72
What cells does the exocrine pancreas contain?
Acinar secretory cells together with centroacinar cells which are unique to the pancreas.
73
Describe the structure of an exocrine pancreatic gland.
The lumen of the acinus (functional unit of the gland) leads to an intercalated duct lined with simple cuboidal epithelium. The ducts are nonstriated and converge to form interlobular ducts lined by stratified cuboidal epithelium.
74
Describe the structure of exocrine pancreas acinar cells.
They are pyramidal cells with round, basally located nuclei, basophilic cytoplasm and well developed RER.
The apices are packed with eosinophilic secretory zymogen granules containing enzymes/proenzymes. These are released into the acinar lumen by exocytosis (merocrine) in response to CCK.
75
Where are centroacinar cells of the exocrine pancreas located?
In the centre of acici and they form the terminal lining of intercalated ducts.
76
What are the main anatomical differences between the parotid gland and the pancreas?
- The presence of striated ducts in the parotid but not the pancreas.
- Presence of centroacinar cells in the pancreas only.
- Islets of Langerhan in the pancreas.
77
What are the principal functions of the liver?
- Protein metabolism
- Carbohydrate metabolism
- Fat metabolism
- Storage
- Detoxification
- Secretion
78
What would you see in a histological section of a portal triad? What do these things make?
- Terminal portal venule of hepatic portal vein
- Terminal branches of hepatic artery
- Lymphatics
- Bile ductules
- Hepatocyte plate (sheet of helpatocytes)
- Sinusoids receiving blood from both hepatic portal vein and hepatic artery.
All make a liver lobule.
79
How many lobules are in the liver?
1 million
80
Describe the structure of a liver sinusoid.
The sinusoid walls are composed of fenestrated epithelium with a narrow space called the space of Disse between the hepatocytes and the endotheilal lining cells of the sinusoid. Within the space of Disse you have microvilli of hepatocytes.
81
What are found within the inner sinusoidal walls?
Macrophages (Kupffer cells)
82
What are Stellate cells?
Also called Ito or hepatic lipocytes are responsible for the production of ECM/meshwork of reticular fibres (collagen type III). This is involved in liver fibrosis.
83
What are the two distinct domains of a hepatocyte?
1) Apical domain represented by the bile pole.
| 2) Basolateral domain which is extensive and has microvilli extending into the space of Disse.
84
What do bile pigments do?
They break down products of worn out blood cells which are either destroyed by macrophages of the spleen or Kupffer cells of the sinusoids.
85
What is a liver acinus?
The functional unit of the liver centred around a central vein and bordered by portal triads.
86
What are the three zones of a liver acinus?
Zone 1 = blood is oxygenated and nutrient rich. Hepatocytes specialised for oxidative liver functions are found here.
Zone 2 = intermediate.
Zone 3 = blood here is depleted of oxygen and nutrients. Hepatocytes are more used for glycolysis, lipogenesis and cytochrome P-450 drug detoxification.
87
What does paracetamol (acetaminophen) toxicity cause in the liver?
Zonal, centrolobular hepatocyte necrosis i.e. extensive damage around central veins. Hepatocytes around portal triads accumulate fat.
88
What does chronic hepatitis B infection cause in the liver?
Cirrhosis. This involves disruption of lobule architecture, extensive fibrosis of portal tracts, lobules and interstitum, loss of inflammatory cells.
89
What happens to the liver as a result of alcohol cirrhosis?
Extensive fibrosis by Stellate cells. Hepatocytes are restricted to small regenerative nodules
90
What are the epithelium lining the gall bladder?
Simple tall columnar epithelium. They have irregular microvilli at the apical surface and basally located nuclei.
91
How does the gall bladder concentrate bile?
By actively transporting NaCl out of the cells on the basolateral border.
92
What are the characteristics of peptide/protein hormone cells?
- Lots of RER
- Golgi
- Secretory vesicles
93
What are the characteristics of steroid-secreting cells?
- Lots of SER
- Abundant mitochondria
- Lipid droplets
94
What are pituicytes?
They are glial-like cells that support the neurons found in the posterior pituitary.
95
What is the function of somatostatin when released by the pituitary?
Blocks GH and TSH release.
96
What is the function of dopamine when released by the pituitary?
Blocks prolactin release.
97
Where would you find simple squamous epithelium?
Capillary endothelium, alveolar wall.
98
What are the two cell types found in the alveolar wall?
- Squamous type 1 pneumocytes.
| - Rounded type 2 pneumocytes that secrete surfactant.
99
Where would you find simple cuboidal epithelium?
They line small ducts and tubules such as the collecting tubules of the kidney and small excretory ducts of salivary glands and the pancreas.
100
What are goblet cells?
Modified columnar epithelial cells that synthesises and secretes mucus.
101
Where are pseudostratified epithelium found?
In the airways of the respiratory system - much of the upper respiratory tract (trachea, bronchi and large bronchioles).
102
What maintains the structure of cilia?
A core of microtubules arranged as 9 pairs surrounding a central pair.
103
Where are stratified epithelium found?
- Oral cavity
- Pharynx
- Oesophagus
- Anal canal
- Uterine cervix
- Vagina
Sites are subject to mechanical abrasion but are kept moist by glandular secretions.
104
What happens to keratin in keratinisation of stratified squamous epithelium?
They become cross-linked by -S-S- bridge.
105
What are the permanent and transient cells of soft connective tissue?
Permanent = fibroblasts, adipose.
Transient = Mast, plasma leukocytes and lymphocytes.
106
What are the functions of adipose cells?
- Large store of energy.
- Subcutaneous layers help shape the body.
- Deposits in pads act as shock absorbers (e.g. soles of feet).
- Fills spaces between tissues and keeps tissues in place.
107
What is loose connective tissue?
A type of soft connective tissue that contains abundant elastic fibres and collagen bundles embedded in ground substance. Also called areolar connective tissue.
108
Where is loose connective tissue found?
In mesentery and is a component of the lamina propria of the digestive and respiratory tracts, stroma of glands and the hypodermis of skin.
109
What is dense connective tissue?
Soft connective tissue that is subclassified according to the orientation of collagen fibres: irregular or regular.
110
What is dense irregular connective tissue?
Course, thick intertwined bundles of collagen fibres arranged in an irregular form.
Found in dermis of the skin.
111
What are the two layers of the skin dermis?
- Papillary (small, towards surface)
| - Reticular (large, deep)
112
What is dense regular connective tissue?
Regularly orientated parallel bundles of collagen fibres separating linear rows of fibrocytes.
Found in tendons and ligaments.
113
Why are elastin and collagen found in ligaments?
Elastin allows the ligament to stretch, but stores energy to help bring the structure back. Collagen is present for tensile strength and to stop overstretching.
114
What two hormones does the kidney synthesise?
- Renin
| - Erythropoietin (stimulates erythrocyte production in bone marrow)
115
What does the renal corpuscle consist of?
- Bownman's capsule
| - Glomerulus
116
How do renal corpuscles develop?
From blind-ended tubules lined by simple cuboidal epithelium. The ends of the tubules dilate and invaginate as they associate with mesodermal tissue which will eventually differentiate to form the glomerulus.
The layer of invaginated epithelium flattens and differentiates into podocytes which fuse with the basal laminae of glomerular endothelila to form the glomerular basement membrane.
117
What is the mesangium?
A structure found in the glomerulus that is continuous with the smooth muscles of kidney arterioles. It is found outside the capillary lumen.
118
How do podocytes form a filter?
They have primary and secondary processes called pedicels that completely cover the endothlia of the glomerulus. The interdigitation of these processes gives rise to regularly spaced filtration slits of uniform width.
119
What epithlia make up the primary convoluted tubule?
Simple cuboidal epithelium with a large brush border of tall microvilli and numerous mitochondria.
120
What are the differences between the proximal and distal convoluted tubules on the cellular level?
DCT has larger more prominent lumen, no brush border and smaller cells.
121
What are the cellular characteristics of the principal cells of the collecting duct?
- Pale cytoplasm
- Scanty organelles
- Short microvilli
122
What are the cellular characteristics of the intercalated cells of the collecting duct?
- Dark cytoplasm
- Many mitochondria
- Polyribosomes and vesicles
123
What are collecting tubules?
An extension of the DCT, several of which converge to form a collecting duct.
They are lined by a mixture of DCT cells, collecting tubule cells principal cells and intercalated cells.
Simple cuboidal epithelium become increasingly tall distally as they merge is the columnal epithelium of the collecting duct.
124
Describe the pathway of the collecting duct to the renal pelvis.
The collecting duct descends as medullary rays towards the renal medulla, merging to form larger ducts of Bellini that drain urine from the tip of the renal papilla into the renal pelvis.
125
What is the role of the juxtaglomerular apparatus?
Regulates blood pressure via the renin-angiotensin-aldosterone system.
126
What is the pelvicalceal space?
Another word for the renal pelvis.
127
What are the two layers of smooth muscle in the ureter?
1) Longitudinal = inner layer and elongated spiral.
| 2) Circular = outer layer and tight spiral.
128
What lines the lumen of the ureter?
Transitional epithelium with deep lamina propria rich in collagen.
129
What does the wall of the bladder consist of?
Three muscle layers:
- Inner longitudinal
- Outer circular
- Outermost longitudinal
Abundant elastic fibres.
130
What does the adventitia of the bladder contain?
Arteries, veins and lymphatics.
131
What does Nissl staining stain for?
All cell bodies (specifically RER, neurons have lots of these)
132
What does silver staining stain for?
Neuron cell bodies and axons.
133
What neurons lie in the ventral horn of the spinal cord?
Motor neurons
134
What lies in the lateral horn of the spinal cord?
Preganglionic neurons
