Microanatomy Flashcards
(110 cards)
1
Q
4 tunics of the digestive system
A
Mucosa
Submucosa
Muscularis externa
Adventitia/Serosa
2
Q
3 layers of mucosa
A
Epithelium
Lamina propria
Muscularis mucosae
3
Q
Adventitia
A
Outermost connective tissue between two adjacent structures
4
Q
Serosa
A
Slippery outer covering for the gut tube between structure and body cavity
5
Q
Mesothelium
A
Layer of serosa attached to organs that produces serous fluid
6
Q
Epithelium fuction
A
Protection (physical and chemical)
Secretion
Absorption
7
Q
Lamina propria function
A
Supportive tissue that allows nutrients to diffuse to avascular epithelium
Both functional and structural support
8
Q
Muscularis mucosae is only found in:
A
Smooth muscle
9
Q
Muscularis muscosae function
A
Provides movement to mucosa independent of peristalsis at a microcellular level
10
Q
Submucosa function
A
Functional and structural support to mucosa
11
Q
2 layers of muscularis externa
A
Inner circular
Outer longitudinal
12
Q
Muscularis externa function
A
Generates peristaltic movement
13
Q
Intraperitoneal organs are covered with:
A
Serosa, lined with a single thin squamous layer of mesothelium
14
Q
Mesothelium is also known as:
A
Visceral peritoneum
15
Q
Retroperitoneal organs are covered with:
A
Adventitia on the posterior surface and mesothelium on the anterior surface
16
Q
Ascites
A
Inappropriate drainage of serous fluid creates pressure, discomfort, abdominal swelling and distortion of visceral organs
17
Q
Peritonitis
A
Physical damage, chemical irritation and bacterial invasion leads to inflammation which interferes with normal functioning
18
Q
Amylase
A
Salivary enzyme that digests carbohydrates
19
Q
Parotid salivary glands
A
Found at upper back of mouth
Only serous acina
Produces 25% of saliva
20
Q
Sublingual salivary glands
A
Found in lower gum underneath teeth
Mixed, but predominantly mucus acina
Produces 5% of saliva
21
Q
Submandibular salivary glands
A
Found in lower jaw
Both mucus and serous acina
Produces 70% of saliva
22
Q
Serous acina produce a _____ secretion
A
Watery
23
Q
Mucus acina produce a _____ secretion
A
Viscous
24
Q
Serous acina features
A
Stain dark due to zymogen granules
Nuclei are centrally located and round
Visible myoepithelial cells
25
Myoepithelial cells
Found in both mucus and serous acina
| Contract and squeeze secretions into surrounding ducts
26
Zymogen granules contain:
Digestive enzymes such as amylase
27
Mucus acina features
Don't pick up stain very well
Nuclei peripheral and squished
Contain myoepithelial cells but very squished to the periphery and hard to see
Contain mucus granules
28
Striated duct features
Intralobular
Lots of mitochondria giving a striated appearance
Generate HCO3- and K+
29
Composition of saliva
```
99% water
Mucins
Bicarbonate ions
Lysozyme
Lactoferrin
Immunoglobulin A
Amylase
Lipase
Haptocorrin
Kallikrein
```
30
Role of mucins
Carbohydrate-rich glycoproteins that provide lubrication and prevents bacterial adhesion
31
Role of bicarbonate in the mouth
Counteracts acidic bacterial secretions and protects from acidic vomit
32
Role of lysozyme
Breaks down bacterial cell walls
33
Role of lactoferrin
Defence against iron dependent bacteria
34
Role of immunoglobulin A in the mouth
Important first line of defence in mucus membranes
35
Role of amylase
Active in pH of 4 - 11
| Breaks down carbs in the mouth
36
Role of lipase
Optimal pH of 4
| Breaks down fats in the mouth
37
Role of haptocorrin
Binds B12 and protects it from acidic stomach environment so it can be absorbed later
38
Role of kallikrein
Serine protease that increases blood flow
39
Xerostomia
Dry mouth
| Can be caused by mumps, salivary duct stones, salivary gland tumours, sjogrens syndrome and medications
40
Hypersalivation
Also known as water brash
| Associated with many medical conditions, medications and toxins
41
Area of digestive tract with a dense adventitia
Oesophagus
Density means not a lot of room for expansion or compression
Everywhere except for 1-2 cm between diaphragm and stomach because this is a retroperiotoneal area
42
Function of oesophagus
Rapid transport of food bolus to stomach through peristaltic contractions.
Straight tube about 25 cm long with thick muscular walls and a protective lining.
Collapsed outline with folds of submucosa when empty, stretched out as food descends to stomach
43
Epithelium of oesophagus
Thick sacrificial stratified squamous epithelium, non-keratinised in humans. Transitions into simple cuboidal/columnar as it approaches stomach.
44
Muscularis mucosae of oesophagus
Absent/rare near upper oesophagus but developed near stomach. Longitudinal smooth muscle and elastic network.
Allows independent movement and folding of mucosa which aids absorption and digestion when needed.
45
Muscularis externa of oesophagus
Thick inner and outer coats not always regularly circular and longitudinal.
Skeletal muscle present at pharyngeal end, smooth muscle only at gastric end.
Upper and lower sphincters. No obvious muscle thickening but some increase in inner muscle coat for tonal contraction.
46
Achalsia
Aperistalsis of the oesophagus
| Failure of lower oesophagul sphincter to relax while swallowing
47
Gastro-oesophageal disease
Acid reflux causing heartburn and dysphagia
48
Barrets oesophagus
Repeated exposure to stomach acid causes cellular shift in lower oesophagus from stratified squamous epithelia to simple columnar epithelia with Goblet cells which can increase susceptibility to oesophageal cancer
49
4 areas of stomach
Cardia
Fundus
Body
Pylorus
50
3 muscular layers of stomach
Innermost oblique
Inner circular
Outer longitudinal
51
Cardiac glands secrete:
Mucus
52
Parietal glands (from fundus and body) secrete:
HCl
Intrinsic factor
Pepsinogen
Somatostatin
53
Pyloric glands secrete:
Pepsinogen
Mucus
Gastrin
Somatostatin
54
Rugae
Transient stomach folds
| Visible when empty but not when full due to stretching
55
Cells of the stomach
```
Simple columnar mucus cells
Mucus neck cells
Undifferentiated stem cells
Parietal cells
Chief cells
Enteroendocrine cells
```
56
Simple columnar mucus cells of stomach
Secrete insoluble alkaline glycoproteins to form a protective mucus bicarbonate barrier, preventing autodigestion
57
Mucus neck cells of gastric glands
Secrete soluble acidic glycoproteins when food is present
58
Parietal cells
Secrete H+ and Cl- to combine in the lumen
HCl sterilises food and acidifies environment, vital for pepsinogen activation
Also secretes intrinsic factor which enables vitamin B12 absorption
59
Chief cells
Secretes pepsinogen from zymogen granules into lumen. Acidity from HCl activates pepsinogen which is cleaved into pepsin
60
Pepsin
Endopeptidase that breaks down proteins into peptides
61
3 types of enteroendocrine cells in the stomach
G cells
D cells
ECL cells
62
G cells
Secrete gastrin which targets parietal and ECL cells
63
ECL cells
Enterochromaffin-like cells
| Secrete histamine
64
D cells
Secrete somatostatin
65
Somatostatin
Inhibits insulin and glucagon secretion
66
3 phases of gastric acid secretion
Cephalic
Gastric
Intestinal
67
Cephalic phase
Occurs at sight/thought of food
PSNS (vagus nerve) stimulation causes ACh and gastrin releasing peptide
Innervate parietal, enteroendocrine, chief and mucus cells
68
Gastric phase
Occurs at arrival of food in stomach
Stimulate stretch and chemoreceptors causing reflexive muscularis contraction
Amino acids and high pH detected by enteroendocrine cells which release gastrin, acting on parietal and chief cells
69
Intestinal phase
Chyme enters duodenum which stimulates duodenal gastrin release and weakly stimulates acid production
70
Cells of the small intestine
```
Columnar absorptive cells (enterocytes)
Goblet cells
Enteroendocrine cells
Undifferentiated cells
Paneth cells
```
71
Enterocytes
Columnar absorptive cells
Microvilli brush border to increase surface area
Membrane studded with digestive enzymes e.g. glycosidases, enterokinases and enteropepsidases
Glycocalyx coat which selectively attracts and repels molecules
72
Goblet cells
Secrete mucus
No microvilli brush border
Mucinogen granules fill apical cytoplasm
Basal nucleus
73
Enteroendocrine cells
Usually release secretions basolaterally into capillaries
| Secretory granules release CCK, serotonin and somatostatin
74
Serotonin actions on small intestine
Increases peristalsis
| Increases intestinal secretions
75
Somatostatin actions
Increased absorption
Increased smooth muscle contraction
Gastrin inhibition
76
CCK actions
Contracts gallbladder
Inhibits gastrin in the stomach
Releases pancreatic enzymes
77
Secretin actions
Released bicarbonate from pancreas and bile
| Inhibits gastrin in stomach
78
CCK stimulation
Fatty acids and amino acids
79
Secretin stimulation
Acidic chyme
80
Paneth cells
TNF-alpha, lysozyme and defensin secretions
81
TNF-alpha
Produces inflammation in response to bacteria and parasites
82
Defensins
Increases ion channels in cell membranes of invading organisms and increases permeability
83
Brunners glands
Only present in duodenum
| Secrete bicarbonate rich mucus
84
Peyers patches
Lymphocyte aggregates found in ileum
Macroscopically visible
Core of B lymphocytes with M cells on the outside
85
Plicae circularis
Circular folds projecting into the lumen of the small intestine
86
Area of the small intestine with the most plicae circularis
Jejunum
87
Main functions of the colon
Reabsorb fluids and vitamins
| Compact feces
88
Caecum
Sac at the beginning of colon that collects and stores arriving materials from the ileocaecal valve and begins the process of compaction
89
Appendix
Slender, hollow tube dominated by lymphoid nodules
90
Mucosa of colon
Smooth, no plicae of villi
Numerous mucosal glands
Dominated by columnar absorptive cells and Goblet cells
91
Intestinal/mucosal glands are also called:
Crypts of Lieberkuhn
92
Columnar absorptive cells of colon
Absorb water and electrolytes
| Absorb vitamins produced by bacteria (B and K)
93
Goblet cell presentation in colon
Become more numerous further down the colon due to increased dehydration of feces requiring more mucus for easy passing
94
Lamina propria of colon
Dense layer of collagen immediately below surface epithelium
| Numerous lymphatic nodules extending down into submucosa
95
Muscularis externa of colon
Circular and longitudinal muscle layers
| Longitudinal muscle layer thickened into three bands called teniae coli
96
Teniae coli
Allow segments of colon to contract independently, pulling it into haustra coli pockets
97
Colon coverings
Adventitia on posterior surface
| Serosa everywhere else
98
Oesophagus germ cells
Located at basal epithelium, migrate up to surface
| Replaced every few days
99
Stomach germ cells
Located near neck of gastric glands, migrate both up and down
Superficial cells replaced every few days, deeper cells less often
100
Small intestine germ cells
Located in the lower crypts of Lieberkuhn, migrate both up and down
Superficial cells replaced every few days, deeper cells less often
101
Large intestine germ cells
Located in lower crypts of Lieberkuhn, migrate up to surface
| Replaced every few days
102
Hepatic lobule
Anatomical hexagonal subunit of liver
103
Liver acinus
Functional division of liver - rhombus shape where blood flows to opposite corners towards central veins
104
Portal lobule
Triangle formed by 3 central veins. Bile flows from central veins towards portal space - opposite direction to blood flow
105
Hepatocytes
Cells of the liver that make up a hepatic lobule. Cells and sinusoids radiate out away from central vein
106
Sinusoid
Very leaky capillary that supplies mixed blood to hepatocytes, then collected by central vein in the middle
Can fit more than one red blood cell through lumen at once
107
Kupffer cells
Specialised macrophages in the liver lining the walls of the sinusoids
Prevent obstruction and provide antibacterial defence
108
Endothelium in liver
Leaky, fenestrated cells that line the sinusoids
| Also have intercellular openings
109
Fat storing cells in liver (pericytes)
Located between endothelial basement membrane and neighbouring hepatocytes
When quiescent - vit A metabolism
When activated - scar tissue formation
110
Bile canaliculi
Membranous infoldings form channels between hepatocytes which drain to bile ductules then into the bile duct in the portal space for gallbladder storage
