Histology Flashcards
1
Q
How does cardiac muscle differ from skeletal muscle?
A
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)
2
Q
What is the function of interrelated discs in the heart?
A
Desmosomes anchor one cardiac muscle to the next by immediate cytoskeleton filaments
Gap junctions allow ion transfer between cardiac smooth muscle electrochemical coupling
3
Q
Describe the histology of purkinje fibres
A
Large modified muscles
Large vacuoles
Few myofibrils therefore pale H&E
Stores of glycogen
4
Q
Describe the histology of the heart valves
A
Thick collagen with occasional elastic tissue. Both surfaces are covered with endothelial cells. Chordea tendinae are fibrous
5
Q
Describe the histology of the pericardium
A
A single layer of mesothelial cells on the basement membrane with thin loose elastic/ fibrous tissue
6
Q
Describe the histology of endocardium
A
A single layer of the heart with endothelial cells on the basement membrane with thin loose elastic/fibrous tissue. This covers the valves
7
Q
What are the three layers of an artery/vein?
A
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
8
Q
What are the features of a muscular artery?
A
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
9
Q
What are the features of an elastic artery?
A
Thick medial layer with concentric sheets of elastic interspersed with smooth muscle.
10
Q
What vessels are elastic artery?
A
Aorta, GT Vessels
11
Q
What are the features of arterioles?
A
3 or fewer layers of muscle in media. No internal elastic lamina. Poor adventitia
12
Q
What are the features of the glandular acinus in the rectal musosa?
A
Lined by enterocytes and goblet cells
Mucosa does not ever contain blood vessels
13
Q
What places have fenestrated capillaries?
A
Gut, kidney, glomerulus, endocrine glands
14
Q
What is the diameter of a capillary?
A
5-10 micrometers (same as an erythrocytes)
15
Q
Where are contractile pericytes found?
A
Capillary bed
16
Q
What are the functions of endothelial cells?
A
Active transport of molecules across cytoplasm
Influence muscle tone
Coagulation
Produce cell adhesion molecules
17
Q
What are the features of venules?
A
Thin walled
Irregular outline
Pericytes alongside them
18
Q
What are the features of small veins?
A
Thin layers and poor boundaries
Irregular outline
Large lumen
19
Q
What are the features of large veins?
A
Thick wall
Distinct layers
Medial layer with longitudinal smooth muscle
Thick adventitia with longitudinally arranged muscle fibres
20
Q
What are the walls of lymph vessels?
A
Connective tissue with some muscle
21
Q
What are the features of a lymph vessel?
A
Less pressure than venules
Sometimes lymphocytes seen
No blood
22
Q
How can reticulocytes be identified on a slide?
A
Immature erythrocytes with some visible ribosomes (dark staining granules)
23
Q
How can eosinophils be identified on a slide?
A
2-3 Lobe nucleus
Bright pink granules
Granular
24
Q
What are the roles of eosinophils?
A
Phagocytosis of foreign material especially associated with parasitic infection
Neutralise histamine
25
How can neutrophils be identified on a slide?
Multi-lobar nucleus
| Granular
26
What are the roles of neutrophils?
Phagocytic
Engulf and destroy bacteria
Leave blood stream to enter tissue at infection site
27
What are in the primary granules of neutrophils?
Lysosomes, acid hydrolases
28
What do the secondary granules of neutrophils do?
Regulation of inflammation response
29
What do the tertiary granules of neutrophils do?
Facilitate insertion of proteins to cell membrane
30
How can basophils be identified on a slide?
Not multilobar nuclei
| Dark blue granules which appear to fill cell
31
What are the roles of basophils?
Secrete histamine
| Similar role to mast cells
32
How can lymphocytes be identified on a slide?
Small cells with dark staining nucleus and little cytoplasm
| B and T are indistinguishable
33
What are the non granular leukocytes?
Lymphocytes and monocytes
34
What are the granular leukocytes?
Eosinophils, basophils, neutrophils
35
How can monocytes be identified on a slide?
Kidney shaped nucleus
No granules
Pale blue cytoplasm
36
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
37
How can platelets be identified on a slide?
Smaller than erythrocytes
Anucleate
Fragments
Blue
38
What are platelets formed from?
Fragments from multinuclear megakaryocytes
39
What are the 4 types of granules in a platelet?
Alpha
Dense
Lysosomes
Peroxisomes
40
What is respiratory epithelium?
Simple/pseudo-stratified columnar ciliated epithelium with non-ciliated stem cells
41
Where is respiratory epithelium found?
The nose, nasopharynx, larynx, trachea, bronchi, bronchioles
42
What are swell bodies and where are they found?
Thin arterioles/venules deep to epithelium in the nose
43
Why is the skin thin in the nose?
To allow the escape of water
44
What does the mucous do on the respiratory epithelium?
Preventing dehydration of epithelium and traps particulate matter
45
Where is the olfactory epithelium found?
The roof of the nose below the cribriform plate
46
Describe the olfactory epithelium
Pseudo-stratified columnar epithelium with basal and sustenacular cells. Bipolar neurons and serous glands present. Special bowmans glands present
47
What are bowmans glands?
Small serous glands below olfactory epithelium
48
What are sustenacular cells?
Tall narrow cells in contact with the basement membrane. Cytoplasm accumulates yellow/brown pigment. Found in olfactory epithelium
49
What is the epithelium on the vocal folds?
Stratified squamous epithelium
50
What is the epithelium on the false folds?
Respiratory type epithelium
51
What is the epithelium on the vestibule?
Respiratory type epithelium
52
What is the epithelium on the trachea?
Respiratory type epithelium
53
What is the vocalis muscle?
Voluntary skeletal muscle in the vocal folds
54
What is the conus elasticus?
A free upper margin of elastic tissue on the vocal folds
55
What colour do goblet cells stain with H&E?
White
56
What type of epithelium is present in the bronchus?
Respiratory epithelium
57
How is the bronchus held open?
Hyaline cartilage framework which appears as isolated islands
58
Describe the bronchus histology
Respiratory epithelium
Held open by hyaline cartilage
Smooth muscle band under epithelium
Lymph nodules (MALT) at connective tissue
59
What is a lymph node?
A discrete encapsulated collection of lymphoid tissue
60
Describe the histology of the bronchioles
```
Respiratory epithelium
Smooth muscle
Lymph nodules
Closely associated arteries and veins
No goblet cells
```
61
Describe the histology of the terminal bronchioles
Simple cuboidal epithelium
Sparsely ciliated
Clara cells- function is secretory and synthetic
Sphincter like smooth muscle ring
62
Describe the histology of the respiratory bronchioles
Simple cuboidal epithelium
| Larger than terminal bronchioles
63
Describe the histology of the alveoli
Respiratory epithelium
Fibroblasts in walls
Adjoining alveoli connected by pores
Type one and type two cells
64
What is a type one alveolar cell?
Thin cells with flat nuclei
| 40% population, 90% surface area
65
What is a type two alveolar cell?
Globular cells secreting surfactants. Rounded dark staining nuclei.
60% population, 10% surface area
66
What do fibroblasts in alvoli do?
Produce type three collagen (reticulin) and elastic tissue (recoil)
67
What do alveolar macrophages do?
Free roam in alveoli and phagocytose particulate matter and cell debris. Formed from monocyte in blood.
68
Where are fixed/septail alveolar macrophages found?
The interstitium between cells and tissue
69
What type of epithelium is in the mouth?
Stratified squamous non-keratinising epithelium
70
What type of epithelium is in the oropharynx?
Stratified squamous non-keratinising epithelium
71
What type of epithelium is in the lip?
Stratified squamous keratinising epithelium
72
Why is there striated skeletal muscle in the deeper layers of the mouth?
To change shape of the oral cavity
73
What are fordyce's spots?
Sebaceous glands in the lip- whitish spots
74
What type of epithelium is on ventral surface of the tongue?
Stratified squamous non keratinising epithelium
75
What type of epithelium is on the dorsal surface of the tongue?
Stratified squamous keratinising epithelium
76
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
77
How do serous glands appear on a slide?
Pink staining- appear as a cluster of grapes with a nucleus on the base
78
What are the complex folds on the dorsal tongue surface known as?
Papillae
79
What are the filiform papillae?
The most common papillae. Tall and pointed. On whole anterior two thirds of tongue
80
What are the fungiform papillae?
Found at the tip and sides of the tongue. Pale staining, spindle shaped taste puds with nerve vesicles
81
What are the circumvallate papillae?
A V shaped row at the margin of anterior 2/3 and posterior 1/3 of tongue
82
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.
83
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)
84
How do parotid duct cells appear on a slide?
Simple cuboidal (stratified at distal end)
85
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
```
86
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
87
What is the epithelium on the epiglottis?
Stratified squamous non-keratinising epithelium (respiratory epithelium on lower posterior part)
88
Describe the histology of the epiglottis
SSNKE (resp epithelium on lower posterior part)
| Contains elastic cartilage plate, lymph nodules, and salivary glands
89
What are the four layers of the GI tract?
1. Mucosa
2. Sub-mucosa
3. External muscle coat (muscularis externa)
4. Serosa
90
What is the GI tract innermost mucosa layer formed of?
Epithelium, lamina propria (connective tissue), and a smooth muscle ring (muscularis mucosa)
91
What is the GI tract's sub-mucosa formed of?
Loose connective tissue, glands, lymphoid tissue, blood vessels, meissner's plexus
92
What is the GI tract's musculris externa formed of?
2 layers of smooth muscle, auerbach's plexus
93
What is the GI tract's serosa formed of?
Simple squamous epithelium
94
What is the muscularis mucosa like in the oesophagus?
Narrow (thicker at gastric end)
95
What is the epithelium in the oesophagus?
SSNKE above diaphragm, simple columnar below diaphragm
96
What does the sub-mucosa of the oesophagus contain?
Sero-mucous glands for lubrication, large thin walled veins
97
What is the muscle of the muscularis externa like in the oesophagus?
Upper 1/3- skeletal
Middle 1/3- Mixed
Lower 1/3- Smooth
98
What are the folds of mucosa in the stomach called?
Rugae
99
What is the epithelium in the stomach?
Simple columnar epithelium
100
How thick is the muscularis externa in the stomach?
3 layers
101
What are the oblique muscle fibres in the stomach for?
Churning
102
Where in the stomach are full gastric glands found?
Body and Fundus
103
Where in the stomach are there no parietal/chief cells found?
Cardia and pylorus
104
What is the submucosa of the stomach body like?
Loose connective tissue with abundant vessels
105
Why does the muscularis mucosa of the stomach contain elastic?
To stop stomach collapse on empty
106
How to parietal cells appear on a slide?
Globular- bright pink with H&E
| Cell surface invaginated with many mitochondria
107
Where in the stomach are parietal cells found?
Gastric glands in the body/ fundus
| Upper part of the gland close to the pits
108
Where in the stomach are chief cells found?
Gastric glands in the body/ fundus
| Close to muscularis mucosa
109
How do chief cells appear on a slide?
Pyramidal
Blue cytoplasm on H&E
Contains granules
110
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
111
Describe the histology of a villi
Simple columnar epithelium
Short life but replaced by crypt population
Contain venule, arteriole, lacteal, smooth muscle
112
Describe the histology of a crypt of lieberkuhn
Between villi
Stem cell population
Migrate to the top and shaved off after 5 days
113
Why does the brush border stain intensely magenta with PAS?
High concentrations of hexose sugars
114
What are brunner's glands?
Mucous secreting gland in the submucosa of the duodenum- alkaline secretion that neutralises chyme
115
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
```
116
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
117
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
```
118
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
119
What is the epithelium of the appendix?
Simple columnar epithelium
120
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
```
121
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
```
122
What is the epithelium in the anal canal?
Stratified squamous epithelium, keratinised at distal end
123
Describe the muscularis externa in the anal canal
Smooth muscle of muscularis externa is thickened and surrounded by striated muscle of external anal sphincter
124
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
125
What are the four lobes of the liver?
Left
Right
Caudate
Quadrate
126
What is the blood supply to the lobules?
70% Portal vein blood
| 30% portal artery blood
127
What are sinusoids?
Wide, thin, fenestrated capillaries
128
What is in the portal triad?
Hepatic artery, hepatic vein, bile duct
129
What is the epithelium of a bile ductule?
Simple cuboidal epithelium
130
What is space of disse?
Area in liver- no blood here but plasma
131
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
132
What are kupffer cells?
Fixed macrophages in the lining of sinusoidal endothelium. Phagocytose blood borne pathogens
133
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
```
134
How are the pancreatic enzymes activated?
Alkaline environment of duodenum
135
How is the exocrine pancreas stimulated to secrete alkaline fluid from centro-acinar and small duct cells?
Secretin
136
What is the pacinian corpuscle?
The pressure sensor in the pancreas
137
What is the epithelium in the exocrine pancreas?
Simple cuboidal epithelium
138
Give 3 examples of fixatives that can be used to fix a specimin
Formalin
Alcohol
Acid
139
What is used to dehydrate tissues?
Alcohol
140
How thick are the slices of specimins?
2-10 micrometres
141
How are blood samples viewed histologically?
Smears
142
What does haematoxylin stain?
Nuclei and RNA = blue
143
What does eosin stain?
Cytoplasm, fibres, colloidal protein= Pink
| Keratin= Orange/Red
144
What does iron haemotoxylin stain?
Nuclei and elastic fibres= Black
145
What does alcian blue stain?
GAG-rich structures, mucous goblet cells, mast cell granules, cartilage, matrix= Blue
146
What does Period acid schiff stain?
Hexose sugars= Magenta
147
What does Perl's stain stain?
Ferric iron= Prussian blue
148
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
149
What does Toluidine blue stain?
Nuclei, ribosomes = Dark blue
Cytoplasm, cartilage, matrix= pale blue
Mat cell granules, GAG rich components= Bright purple
150
What does Van gieson stain?
```
Collagen= Pink/Red
Cytoplasm= Yellow/Green
Nuclei= Black
```
151
What are all the 6 cell shapes?
```
Rounded
Polygonal
Fusiform
Squamous
Cuboidal
Columnar
```
152
What are the 5 tissue types?
Epithelia, muscle, supporting tissue, nerves and germ cells
153
What is the difference between euchromatin and heterochromatin?
Euchromtin is lightly packed and heterochromatin is tightly packed
154
Where is the site of lipid synthesis?
The mitochondrial outer membrane and smooth ER
155
Where is the site of the ETC chain?
The mitochondrial inner membrane
156
Where is the site of the Krebs cycle?
The mitochondrial matrix
157
Where is the site of nucleotide phosphorylation?
The intermembranous space of the mitochondria
158
Where is the site of protein synthesis?
Rough ER
159
Where is the site of proteolysis?
Trans golgi network
160
Where are vesicles recieved?
The cis face of the golgi
161
Where are olgiosaccharides formed?
The medial golgi
162
What is the role of perioxiomes?
Oxidise long chain fatty acids
163
What is lipofuscin?
An orange-brown pigment from peroxidation of lipids in older cells- common in heart and liver of older patients
164
How long are tubulin proteins?
25nm
165
How long are actin microphilaments?
5nm
166
How long are intermediate filaments?
10nm
167
Where is simple squamous epithelium found?
Blood vessels, the outside of the lungs, abdominal organs
168
Where is simple cuboidal epithelium found?
The kidney tubules, small ducts
169
Where is simple columnar epithelium found?
The stomach, intestines and uterus
170
What filaments are microvilli formed of?
Actin and Myosin
171
What filaments are cilia formed of?
Tubulin and dynein
172
Where is stratified epithelia found?
Sites of abrasion- skin, vagina, mouth
173
Where is stratified squamous non-keratinising epithelium found?
Mouth, oropharynx, vagina
174
Where is stratified squamous keratinising epithelium found?
The skin
175
What does keratin do to an epithelium?
Waterproof it
176
Where is pseudostratified epithelium found?
The conducting airways
177
What types of epithelium can have cilia?
Simple columnar epithelium, pseudostratified epithelium
178
What extra-cellular proteins are present in a basement membrane?
Collagen IV and fibronectin
179
What stain will make basement membranes visible?
PAS
180
What are occluding (tight) junctions?
Band-like fusions between cells that are impervious to most molecules
181
What are desmosomes?
Plaques that form physical joints between cells and connect the cytoskeletons of adjacent cells
182
What are gap junctions?
Electrical junctions that permit the transfer of small molecules
183
What is the origin of connective tissue cells?
- Usually undifferentiated mesenchymal cells e.g. fibroblasts
- Some from haematopoetic stem cell line e.g. monocytes
184
What molecules are present in the ground substance?
Proteogylcans, GAG, Invisible fibres like laminin
185
What is collagen secreted from?
Fibroblasts
186
Are collagen fibres produced extracellularly or intracellularly?
Extra-cellularly
187
Where is type I collagen normally found?
Skin and bone
188
Where is type II collagen normally found?
Cartilage
189
Where is type III collagen normally found?
Liver, bone marrow, spleen (reticulin)
190
Where is type IV collagen normally found?
Basement membrane
191
Where is type V collagen normally found?
Placenta
192
How is collagen viewed on H&E?
Extracellular fibres that stain pink. Variable thickness and length. Often run in bundles
193
What is loose connective tissue comprised of?
Widely spaced, thin collagen fibres and the fibroblasts that secrete them. Inbetween this is unstained ground substance
194
What is dense connective tissue comprised of?
Densely packed thick collagen fibres, and the fibroblasts that secrete them. Some unstained ground substance
195
What are the two types of dense connective tissue?
Regular and Irregular
196
Where is regular dense connective tissue found?
Tendons
197
Where is irregular dense connective tissue found?
Fascia of penis
198
What is reticuin?
Type III collagen- forms a supporting scaffold in many organs e.g. bone marrow, liver, kidney, spleen
199
What stain is used for reticulin?
Silver stain
200
What is elastin?
Elastic tissue containing fine fibres and sheets of elastin. It is produced by fibroblasts.
201
What stain is used for elastin?
H&E
202
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
203
Where is brown adipose tissue found?
Across the shoulders and down the back of newborns- important in neonatal thermoregulation (generates heat on breakdown)
204
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
205
Describe the histological appearance of brown adipose tissue
Many fat globules per cell, with multiple vacuoles. Generally a pink "foamy" appearance
206
What cells are found in cartilage?
Chondroblasts and chondrocytes
207
Is cartilage vascular or avascular?
Avascular- derives its blood supply from vessels either side of the cartilage
208
Where is hyaline cartilage found?
Synovial joints
209
Describe the histological appearance of hyaline cartilage
Chondrocytes in lacunae surrounded by a glassy amorphous blue/grey matrix with no visible fibres
210
Where is elastic cartilage found?
The pinna of the ear and the epiglottis
211
What is found in the the perichonrium of hyaline, elastic and fibrocartilage?
Fibroblasts and collagen
212
Describe the histological appearance of elastic cartilage
Visible elastic fibres in a blue/grey matrix
213
What stain is used for elastic cartilage?
H&E can be used, but it is more visible with silver stain
214
Where is fibrocartilage found?
Annulus fibrosis of spine and pubic symphysis
215
Describe the histological appearance of fibrocartilage
Visible collagen fibres in matrix
216
Where is synovium found?
The inside of the joint capsule
217
How many layers of synovial cells are in the synovium?
1-4 layers
218
What are the type A and type B cells in synovium?
Type A- phagocytes
| Type B- cells rich in rER that secrete synovial fluid
219
Is synovium vascular or avascular?
Richly vascular
220
Where is smooth muscle found?
The walls of blood vessels, tube of intestine and bronchioles
221
Describe the histological appearance of smooth muscle
Individual cells with oval/ circle nucleus
| Set in eosynophilic cytoplasm with no striations
222
State the layers of an artery wall going from lumen outwards
1. Lumen
2. Endothelium
3. Basement membrane
4. Intima
5. Internal elastic lamina
6. Media
7. External elastic lamina
8. Adventitia
223
What is the intima?
A thin layer of connective tissue- the next layer after the lumen
224
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
225
What is the internal elastic lamina?
A layer of elastic tissue bounding the intima
226
What is the adventitia?
The final layer of an artery wall, formed of loose elastic tissue
227
Name an elastic artery
The aorta
228
Describe the media of an elastic artery
A thick layer of connective tissue, containing abundant concentric sheets of elastin
229
Are most arteries muscular or elastic?
Muscular
230
Describe the media of a muscular artery
A thick layer of connective tissue, comprising of smooth muscle and has a little elastin
231
Name two muscular arteries
The radial artery and the splenic artery
232
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
233
What are pericytes?
A layer of cells on the outside of capillaries and venules which regulate their size
234
What is a fenestrated capillary?
When the endothelial layer is incomplete. This facilitates movement in and out of capillaries.
235
What are the layers of a capillary wall
Endothelium
Basement membrane
Pericyte
236
Where are fenestrated capillaries found?
The kidneys and liver
237
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.
238
What are pericytes replaced with as venules become veins?
Smooth muscle
239
Is the smooth muscle in veins circular or longitudional?
Can be either !
240
What vessels have valves?
Veins and lymphatics
241
What does lymphatics contain?
Eosinophilic lymph (fluid derived from plasma) and may contain lymphocytes
242
What cells produce myelin?
Schwann cells
243
What is endoneurium?
Connective tissue present between individual axons
244
What is perineurium?
Connective tissue surrounding groups of axons to form fasicles
245
What is epineurium?
Connective tissue binding fasicles to form nerve fibres
246
What stain can be used for myelin?
Silver stain
247
What is myelin?
A spiral of apposed schwann cell membranes that insulate the axon
248
What are nodes of ranvier?
Gaps between schwann cells that allow for saltatory conduction
249
Where are the cell bodies of motor neurons found?
In the grey matter of the spinal cords
250
Where are the cell bodies of sensory neurons found?
The dorsal root gangion
251
Where are the cell bodies of sympathetic neurons found?
In the grey matter of the spinal cord and in adjacent sympathetic ganglia
252
Where are the cell bodies of parasympathetic neurons found?
The brain and local ganglia of organs
253
What are the four principle components of the urinary tract?
Kidneys
Ureters
Bladder
Urethra
254
How many nephrons are approximately in one kidney?
One million
255
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
```
256
What are the 3 layers of the kidney?
Cortex
Medulla
Pelvis
257
What aspects of the nephron are primarily found within the cortex of the kidney?
Glomeruli
Proximal convoluted tubule
Distal convoluted tubule
Medullary rays
258
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)
259
What aspects of the nephron are primarily found within the medulla of the kidney?
Loops of henle, collecting ducts, and blood vessels
260
What is a glomerulus?
A tuft of convoluted fenestrated capillaries, supported by mesangial cells and encased within the Bowman's capsule
261
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
262
What are the two cell types found at the glomerulus?
Capillary endothelial cells and mesengial cells (lie inbetween the capillaries)
263
What stain can be used to see the glomerular basement membrane?
Periodic acid schiff (PAS)
264
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.
265
What are the layers of the glomerular basement membrane?
Lamina lucida interna
Double thickenss lamina densa
Lamina lucida externa
266
Why are Heparan sulfate molecules found in the glomerular basement membrane?
To repel negatively charged ions in the plasma
267
What are the two components associated with the juxtaglomerular apparatus?
The afferent arteriole and distal convoluted tubule
268
How is the afferent arteriole associated with the juxtaglomerular apparatus?
It contributes granular cells that secrete renin in response to low blood pressure
269
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.
270
What are the three cell types present in the juxtaglomerular apparatus?
Lacis cells
Macula Densa
Granular cells
271
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.
272
What is the role of the proximal covoluted tubule?
Reabsorption of NaCl proteins, polypeptides, amino acids, glucose
273
What is the difference between the epithelium of the thin and thick segments of the loop of henle?
Thin- simple squamous
| Thick- Low cuboidal
274
Describe the histological appearance of the distal convoluted tubule
Low cuboidal epithelium rings with scanty microvilli- no prominant brush border. Numerous mitochondria.
275
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.
276
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
277
What is the role of collecting duct?
Water reabsorption, sodium balance and acid base balance.
278
What are the two types of epithelial cell present in the collecting duct?
Principal cell and intercalated cells
279
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)
280
What is the role of the intercalated cells of the collecting duct?
To exchange H+ for HCO3-
281
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
282
What is the epithelium of the renal pelvis?
Urothelium
283
What is the role of the renal pelvis?
Transmits filtrate from nephron to ureter
284
Describe urothelium
Complex stratified epithelium- A layer of umbrella cells overlying a pseudostratified layer of polygonal cells
285
What are the 3 layers of urothelium?
1. Large dome-shaped umbrella cells
2. Intermediate layer
3. Basal layer- cuboidal cells
286
In the GI tract, is the muscle circular on the inner or outer layer?
Circular on the inner layer
287
In the ureter is the muscle circular on the inner or outer layer?
Circular on the outer layer
288
Do ureters have a serosa?
No
289
What are the layers of the bladder?
```
Urothelium
Lamina propria
(poorly developed) Muscularis mucosa
Submucosa
(Well developed) Muscularis propria
Subserosa and serosa
```
290
How many muscular layers are there in the muscularis propria of the bladder?
3
291
How long is the urethra in females?
4-5cm
292
What is the epithelium of the female urethra?
Proximally- urothelium
| Distally- Non-keratinising squamous epithelium
293
What glands open into the female urethra?
Paraurethral and periurethral
294
How long is the male urethra?
15-20cm
295
What are the three parts of the male urethra?
1. Prostatic urethra (3cm)
2. Membranous urethra (1cm)
3. Penile urethra (16cm)
296
What is the epithelium of the male urethra?
Prostatic and membranous urethra- urothelium
| Penile urethra- Pseudostratified epithelium proximally and stratified squamous epithelium distally.
297
What is the average weight of the testis?
15-19g
298
What are the three layers that form the capsule around the testis?
- Tunica vaginalis
- Tunica albuginea
- Tunica vasculosa
299
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
300
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
301
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
302
Where do spermatazoa form?
The seminiferous tubules
303
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
```
304
How many lobules are there roughly in the testis?
250
305
What does the septa between lobules of the testis form from?
The capsule of the testis
306
How many seminiferous tubules are there per lobule?
1-4
307
What are the three types of spermatogonia?
Type A darkly stained cells
Type A pale stained cells
Type B differentiating cells
308
What is the role of type A dark cells in the testis?
Stem cell population
309
What is the role of type A pale cells in the testis?
Develop into type B cells
310
Describe the histological appearance of type B cells in the testis
Spherical nuclei with densely stained masses of chromatin
311
What is the order of development of sperm?
```
Spermatogonia
Primary spermatocytes
Secondary spermatocytes
Spermatids
Spermatozoa
```
312
Where are sertoli cells found?
Resting on the basement membrane of the seminiferous tubule
313
Describe the histological appearance of sertoli cells
Columnar cells with irregularly shaped nuclei; folded and with a prominent nucleolus. Eosinophilic cytoplasm
314
What are the roles of sertoli cells?
Supportive, phagocytic and secretory functions- androgen binding protein and inhibin
315
What structures are present in the head of the spermatozoa?
Acrosomal cap and nucleus
316
What structures are present in the midpiece of the spermatozoa?
Spiral mitochondria wrapped around an axoneme
317
What structures are present in the tail of the spermatozoa?
Neck- centrioles
| Axoneme surrounded by a plasma membrane
318
Where are leydig cells found?
Singly or in clusters in the interstitium between seminiferous tubules
319
What are the roles of leydig cells?
Secrete testosterone
320
Describe the histological appearance of leydig cells
Cells with abundant cytoplasm containing lipid containing reinke's crystalloids (intracytoplasmic eosinophilic crystalloids found after puberty)
321
What is the rete testis?
An anastamosing network of tubules at the hilum of the testis that receive luminal contents from seminiferous tubules
322
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.
323
What are the roles of the rete testis?
- Mixing chamber for contents of the seminiferous tubules
| - Reabsorption of protein from luminal contents
324
How many efferent duct are present in the testis?
12-15
325
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
326
How long is the epididymis?
4-5cm but highly convoluted so roughly 5m in tubular length
327
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
328
What are the roles of the epididymis?
- Absorption of testicular fluid
- Phagocytosis
- Production of secretions for spermatozoa maturation
329
How long is the vas deferens?
30-40cm
330
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
331
What are the lobes of the prostate?
Anterior, middle, posterior and two lateral
332
What are the regions of the prostate?
Peripheral, central, transitional and peri-urethral gland regions
333
How many acini are present within the prostate?
30-50 tubuloalveolar glands with convoluted edges
334
What cells line the acini of the prostate?
Secretory cells, basal cells (form a continuous layer) and neuroendocrine cells
335
What do secretory cells of the luminal side of the prostate gland secrete?
Phosphate-specific antigen, Acid phosphotases, citric acid, amylase, and other proteins
336
What is the role of phosphate specific antigen?
Liquifies semen after ejaculation
337
What structures are present in the stroma of the prostate?
Smooth muscle, fibroelastic fibres, blood vessels and nerves
338
What cell type lines the seminal vesicles?
Tall non-ciliated columnar epithelium, containing vacuoles and lipofuscin
339
How much of the ejaculate is formed of seminal vesicle secretion?
70-80%
340
What does seminal vesicle secretion contain?
Fructose, prostaglandins, proteins, amino acids, citric acid and vitamin C
341
What is the role of the seminal vesicle?
Produce secretion to act as nutrients for the spermatozoa
342
Where does the seminal vesicle duct drain into?
The ejaculatory duct
343
What are the 3 components of the erectile tissue?
2 x Corpora cavernosa
| Corpus spongiosum
344
What is the corpora cavernosa?
Two richly vascular components of erectile tissue lying within the dorsal side of the penis.
345
What is the copus spongiosum?
A component of erectile tissue on the inferior side of the penis and surrounding the urethra.
346
Describe the histological appearance of erectile tissue
Irregular vascular spaces seperated by fibroelastic tissue and smooth muscle
347
How is the ovary attached to the broad ligament?
The mesovary
348
How is the ovary attached to the uterus?
The utero-ovarian ligament
349
How is the ovary attached to the pelvic wall?
The suspensory ligament
350
What is the outside layer of the ovary like?
A single layer of modified mesothelium
351
What is the tunica albuginea in a female?
A poorly defined connective tissue layer in the ovary
352
In which layer of the ovary are the ovarian folicles found?
The cortex
353
Describe the histological appearance of the ovarian cortex
Spidle stromal cells arranged in whorls with ovarian follicles and some leutinised cells
354
Describe the histological appearance of the ovarian medulla
Loose fibroelastic tissue with blood vessels, lymphatics and nerves.
355
What is the rete ovarii?
An analogue of rete testis- present at the hilum of the ovary
356
Where are primordial follicles found?
At the periphery of the cortex
357
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)
358
In the menstrual cycle, how many primordial follicles begin to develop?
30-40
359
What hormone controls the development of a primordial follicle into a primary follicle?
FSH from the anterior pituitary
360
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
361
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)
362
What is the the name of the stalk of granulosa cells that supports the oocyte in the antrum in a secondary follicle?
Cumulus oophorus
363
What are the two layers of connective tissue in a secondary ovarian follicle?
Theca interna and theca externa
364
What is the Theca interna of a secondary follicle?
The inner layer of stroma, comprising of stromal cells which have enlarged and contain lipid
365
What do the stromal cells of the theca interna secrete?
Oestrogen
366
What is the theca externa of a secondary follicle?
The outer layer of the stroma comprising small stromal cells
367
What is the corona radiata in a graafian follicle?
A layer of granulosa cells surrounding the oocyte
368
What surrounds the ovum in a graafian follicle?
A thick zona pellucida
369
How many primordial follicle are present at birth?
Approximately 1 million
370
What hormone triggers ovulation?
Leutinising hormone
371
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
372
What does the secondary follicle develop into after ovulation?
Corpus luteum
373
What hormones does the corpus luteum secrete?
Progesterone and oestrogen
374
How many days after ovulation does regression of the corpus luteum occur?
8-9 days
375
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
376
What does the corpus luteum regress into?
The corpus albicans
377
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
378
What are the roles of the fallopian tube?
To transport the ovum to the uterus
| To be the site of fertilisation
379
In which ligament does the fallopian tube run?
The broad ligament
380
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)
381
What are the branching folds of the mucosa of the fallopian tubes called?
Plicae
382
What are the two cell types in the mucosa of the fallopian tube?
Secretory and ciliated
383
Is the inner muscularis layer of the fallopian tube circular or longitudional?
Circular
384
At which end of the fallopian tube are ciliated cells more prominant?
The ovarian end
385
What are the three layers of the wall of the uterus?
Endometrium
Myometrium
Serosa
386
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
387
What layer of the uterus is shed in menstruation?
The stratum spongiosum of the endometrium
388
What hormone stimulates the proliferative phase of the menstrual cycle?
Oestrogen
389
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
390
What hormone stimulates the secretory phase of the menstrual cycle?
Progesterone
391
How can the endometrium of the early secretory phase be recognised?
The epithelial cells of the endometrial glands contain vacuoles of glycogen
392
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.
393
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.
394
How can the endometrium of the menstrual phase be recognised?
Stromal haemorrhage and granulocytes
| Stromal and glandular fragmentation
395
What triggers the menstrual phase?
Progesterone stimulation being withdrawn
396
What are the different phases of the endometrium in the menstrual cycle?
Proliferative
Secretory (early, mid, late)
Menstrual
397
What is the muscular wall of the uterus?
Myometrium- 3 ill defined smooth muscle layers
| Inner longitudinal, middle circular, outer longitudinal
398
What are the two components of the cervix?
Endocervix and ectocervix
399
Describe the histological appearance of the endocervix
Loose fibromuscular stroma lined by simpled columnar ciliated epithelium, thrown into crypts
400
Describe the histological appearance of the ectocervix
Dense smooth muscle stroma lined by non-keratinised stratified squamous epithelium
401
What is the site of the cervix which most cervical cancers occur?
The transformational zone (squamocolumnar junction)
402
What epithelium lines the vagina?
Non keratinising stratified squamous epithelium
403
How many muscular layers are there in the vagina?
2- inner circular and outer longitudinal
404
What epithelium lines the labia majora?
Keratinising stratified squamous epithelium with skin adnexae
405
What epithelium lines the labia minora?
Non-keratinising stratified squamous epithelium
406
What are bartholin's glands?
Tubuloalvolar glands in the vulva. Acini are lined by mucus-secreting epithelium
407
What are minor vestibular glands?
Simple tubular glands lined by mucus-secreting epithelium in the vulva
408
What are skein's glands?
Female analogous to the prostate, lined by pseudostratifeid columnar epithelium
409
What epithelium lines the hymen?
Non-keratinising squamous epithelium
410
What is the clitoris?
Erectile tissue rich in blood vessels and nerves
411
What are the functions of the skin?
- Barrier to infection
- Waterproofing
- Thermoregulation
- Protection against trauma
- Protection against UV- light
- Vitamin D synthesis
- Sensation
412
What is the outermost layer of the skin?
The epidermis stratum corneum
413
What are the layers of the epidermis?
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum corneum
414
What are the two types of cells present in the stratum basale?
Basal epithelial cells (Stem cell population)
| Melanocytes (Produce melanin)
415
In which layer of the skin are melanocytes found?
The basal layer of the epidermis
416
What is the approximate density of melanocytes?
1000-2000 per mm^2
417
Where does melanin get transferred to after being synthesised?
To keratinocytes in melanosomes
418
What hormones trigger the production of melanin?
MSH and ACTH
419
What is the role of melanin?
To absorb ultraviolet light, protecting us from non-ionising radiation damage
420
What alters the colour of someone's skin?
The amount and type of melanin synthesised (NOT the number of melanocytes)
421
Which layer of the epidermis is the largest?
Stratum spinosum
422
What cells are present in the stratum spinosum?
- Plump, polygonal keratinocytes with prominant intracellular adhesion
- Langerhans cells- antigen recognition
- Merkel cells- Sensory
423
What cells are present in the stratum granulosum?
Flattened squames with an eosinophilic cytoplasm, containing haematoxophilic kerato-hyaline granules
424
In which layer of the skin is keratin synthesised?
The stratum granulosum
425
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)
426
What is the extra layer in the epidermis found between the stratum corneum and stratum granulosum at sites of abrasion?
Stratum lucidum
427
What are epidermal adnexae?
Downgrowths of the epidermis into the dermis
428
What is found within the epidermal adnexae?
Hair follicles
Sebaceous glands
Eccrine sweat glands
Apocrine sweat glands
429
Where are sebaceous glands found?
Accompanying hair follicles
430
What do sebaceous glands secrete?
Holocrine secretion (whole cells)- produces sebaceous secretion which lubricates and waterproofs hairs
431
Where are apocrine glands found?
Armpit, groin, genitals, around the anus, in the ear - accompanying hair follicles
432
Describe the histological appearance of apocrine glands
Simple, coiled, tubular glands, with an eosinophilic cytoplasm- with surface budding
433
What do apocrine glands secrete?
An apocrine secretion- elements of the cytoplasm of the cells- pheromones ??
434
What are the commonest type of sweat glands?
Eccrine glands
435
What do eccrine glands secrete?
An eccrine (merocrine- exocytosis) secretion- thin and watery
436
Described the histological appearance of eccrine glands
Coiled tubes, 2 cell layers thick- inner layer is secretory, outer layer is myoepithelial
437
Where are eccrine sweat glands found?
Everywhere
438
What are rete pegs/ridges?
Where the epidermis protrudes downwards into hte underlying dermis at the dermo-epidermal junction
439
What is the papillary dermis?
The space between the rete pegs
440
What is the thickest layer of the dermis?
The reticular dermis
441
Where are the blood vessels and nerves of the skin found?
The dermis
442
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
443
What can Meissner's corpuscles detect?
Fine touch
444
How long are meissner's corpuscles?
30-140 micrometres
445
What are meissner's corpuscles?
Encapsulated unmylenated nerve endings that detect fine touch
446
Where are meissner's corpuscles found?
In the dermal papillae (especially in hairless skin)
447
Describe the appearance of pacinian corpuscles
Large (1-4mm) long encapsulated sensory receptors- appear as concentric rings
448
Where pacinian corpuscles found?
In the deep dermis
449
What can pacinian corpuscles detect?
Vibration and tickle
450
What is the subcutis formed of?
Adipose tissue and fibrovascular septa
451
What are the roles of the subcutis?
Insulation
Shock-absorber
Food store
452
Where do all the ducts of the breast empty?
At the nipple
453
Describe the terminal duct lobular unit of the breast
Lobules arranged around a terminal duct, set in loose fibrous connective tissue
454
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)
455
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
456
What does the posterior pituitary store/secrete?
Oxytocin
| Antidiuretic hormone
457
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
458
What percentage of pituicytes are somatotrophs and what do they secrete?
50%
| Growth hormone
459
What percentage of pituicytes are lactotrophs and what do they secrete?
25%
| Prolactin
460
What percentage of pituicytes are corticotrophs and what do they secrete?
15-20%
| ACTH, alpha-MSH, beta-lipotrophin, beta-endorphin
461
What percentage of pituicytes are gonadotrophs and what do they secrete?
10%
| FSH and LH
462
What percentage of pituicytes are thyrotrophs and what do they secrete?
1%
| Thyroid stimulating hormone
463
What stain allows you to see the nests of pituicytes within the anterior pituitary?
Reticulin stain
464
Where are somatotrophs normally found within the anterior pituitary?
Primarily at the lateral wings, but can be found throughout
465
Describe the histological appearance of lactotrophs
Polygonal cells with cytoplasmic processes that wrap around other cells
466
Describe the histological appearance of thyrotrophs
Elongated cytoplasmic processes, that don't wrap around other cells
467
Describe the histological appearance and staining of gonadotrophs
Scattered round/oval cells that stain with either alpha subunit, beta LH or Beta FSH
468
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.
469
Where are corticotrophs most likely to be found within the anterior pituitary?
The median of the gland
470
What are susetentacular cells?
Supporting cells within the anterior pituitary that surround the normal follicles - S100 +ve
471
What does the pineal gland secrete?
Melatonin
472
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
473
What is brain sand?
Areas of accumulation of calcium within the pineal gland
474
What cells are present within the thyroid?
Follicular cells with colloid, and C cells
475
What hormones does the thyroid produce?
Thyroxine and calcitonin
476
What do thyroid follicular cells secrete?
Colloid and thyroxine
477
What do follicular C cells secrete?
Calcitonin
478
How many parathyroid glands are there usually?
4
479
What hormone does the parathyroid glands secrete?
Parathyroid hormone (PTH)
480
What are the three cell types present in the parathyroids?
Chief cells
Oxyphils
Adipocytes
481
Describe the histological appearance of the parathyroid chief cells
Small polygonal cells with scant cytoplasm. No calcium oxalate crystals (unlike thyroid)
482
What is the role of the parathyroid's chief cells?
To secrete PTH, which raises the serum calcium using the bone, kidney and gut
483
Describe the histological appearance of the parathyroid oxyphil cells
Large polygonal cells, that increase with age. Abundant eosinophilic cytoplasm that is finely granular.
484
Where are the islets of Langerhans most prevalent?
The pancreatic tail
485
Describe the histological appearance of the Islets of Langerhans
Large, pale staining balls of cells with a thin fibrous capsule
486
What are the four cell types within the endocrine pancreas?
Beta cells
Alpha cells
Delta cells
PP cells
487
What percentage of cells in the endocrine pancreas are beta cells and what do they secrete?
70%
| Insulin
488
What percentage of cells in the endocrine pancreas are alpha cells and what do they secrete?
20%
| Glucagon
489
What percentage of cells in the endocrine pancreas are delta cells and what do they secrete?
5-10%
| Somatostatin
490
What percentage of cells in the endocrine pancreas are PP cells and what do they secrete?
1-2%
| Pancreatic polypeptide
491
What are the three layers of the adrenal cortex (outside to inside)?
Zona glomerulosa
Zona fasciculata
Zona reticularis
492
What does the zona glomerulosa of the adrenal cortex secrete?
Mineralocorticoids - Aldosterone
493
What does the zona fasiculata of the adrenal cortex secrete?
Glococorticoids- Cortisol
494
What does the zona Reticularis of the adrenal cortex secrete?
Androgenic steroids
495
Which layer of the adrenal cortex is the thickest?
Zona fasciculata
496
Describe the appearance and staining of the adrenal medulla
Centre of the adrenal gland, with chromaffin cells- large, polyhedral
S100 +ve
497
What does the adrenal medulla secrete?
Adrenalin and noradrenalin
498
What cells are embryonic skeletal muscle cells derived from?
Myoblasts
499
What is a syncytium?
Multiple embryonic myoblasts fuse to form multi-celled syncytium
500
What is a myofibril?
Multiple sarcomeres joined end to end
501
What is the average diametre of a skeletal muscle fibre?
50-60 Micrometres
502
What is sarcoplasm?
Glycogen-rich cytoplasm in skeletal muscle
503
What is sarcolemma?
The cell membrane of a muscle cell
504
What is sarcoplasmic reticulum?
Endoplasmic reticulum in a muscle cell
505
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
506
Why is striated muscle striated?
The myofibrils are in register!!!!!!!
507
Which section of a sarcomere is dark?
The a-band (myosin)
508
Which section of a sarcomere is light?
The i-band (actin)
509
What are type 1 skeletal muscles?
Slow twitch fibres, rich in fibrillar ATPase - derive energy from oxidative phosphorylation, fatigue resistant
510
What are type 2 skeletal muscles?
Fast twitch fibres, either derive energy from oxidative phosphorylation (Fatigue resistant), or glycolysis alone (fatiguable)
511
Where are type 1 skeletal muscles fibres found?
Muscles for posture (fatigue resistant)
512
Where are type 2 skeletal muscle fibres found?
Muscles for short bursts of power
513
What are muscle spindles formed of ?
Intrafusal muscle fibres wrapped around by gamma efferent nerve fibres, and encased in a fibrocollagenous capsule
514
What is the role of muscle spindles?
To detect stretch and tension
515
What are the three types of connective tissue in skeletal muscle?
Endomysium, perimysium, epimysium
516
What is the role of endomysium in skeletal muscle?
Holds together individual muscle fibres
517
What is the role of perimysium in skeletal muscle?
Binds groups of fibres to form fasicles
518
What is the role of epimysium in skeletal muscle?
Binds fasicles together
519
What are the roles of sharpey's fibres?
Bind epimysium of muscle to periosteum of bone
520
What are sharpey's fibres made of?
Bundles of collagen
521
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
522
Where are tendons found?
In areas where small areas of muscles and bone are connected
e.g. rotator cuff muscles to the humerus
523
What are tendons made of?
Parallel bundles of collagen with intervening fibroblasts
524
What are the four types of cells present in bone?
Osteoprogenitor cells
Osteoblasts
Osteocytes
Osteoclasts
525
What is the extracellular matrix of the bone made of?
Collagen
| Calcium hydroxyapatite
526
What cell type are osteoblasts and osteocytes derived from?
Osteoprogenitor cells (embryonic mesenchyme)
527
What do osteoblasts secrete?
Osteoid (unmineralised bone)
528
How do osteocytes connect to surrounding cells?
Canaliculi
529
What cell type are osteocytes derived from?
Monocytes
530
Describe the histological appearance of osteoclasts
Large, multinucleated bones, sitting on the bone surface
531
What are Howship's lacunae?
Pits in the surface of bone which osteoclasts have absorbed
532
What is the structure of primary and secondary bone?
Primary- woven (haphazard osteoid)
| Secondary- lamellar (parallel sheets of osteoid, forms osteons)
533
What are the two methods of bone formation?
Membranous
| Endochondrial
534
What are the two different types of gross appearance of bone?
Spongy/cancellous
| Compact
535
What is osteoid rich in?
Type I collagen
Glycosaminoglycans
Proteoglycans
536
Where is woven bone commonly found?
Growing bone and fracture sites
537
Is woven bone weak or strong?
Weak
538
What is a haversian canal?
The centre of an osteon, containing blood vessels
539
Which bones form via intramembranous ossification?
The flat bones of the skull and some cortical bone shafts
540
When does intramembranous ossification begin in utero?
The second trimester
541
What are the four layers that form during endochondrial ossification?
Resting cartilage
Zone of hyperplasia
Zone of hypertrophy
Zone of ossification
542
Where is synovium found?
Lining the inside of the joint capsule
543
How many layers of synovial cells are within a joint capsule?
1-4 layers
544
What is the difference between type A and type B synovial cells?
Type A- phagocytes
| Type B- Rich in rER
