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MEDSCI142 > Digestive System > Flashcards

Digestive System Flashcards

1
Q

What are the layers of the tooth from out to in (root and crown)

A

Root: Periodontal ligament, Cementum, Dentin, Pulp
Crown: Enamel, Dentin, Pulp

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2
Q

What is the structure, cells, and function of enamel

A

Cystalline rods or prisms of CaP & carbonate making it the hardest tissue in the body
Has no cells and nerves so lacks sensation and cannot be replaced in adulthood
in the crown only

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3
Q

What is the structure, cells and function of Dentin

A

This is a calcified connective tissue with higher hydroxyapatite content that gives tooth it’s shape.
- Has odontoblasts that are not scattered throughout but near to the pulp.

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4
Q

What is the structure, cells and function of Pulp

A

This is the soft tissue that contains the bv, nerves and lymphatics.
- These nerves contain mechanoreceptors that monitor how much force is on the tooth and stops the tooth getting damaged from excessive force

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5
Q

What is the structure, cells and function of Cementum and Periodontal ligament

A

The periodontal ligament has a large SA to secure the tooth root to the bone of the socket (alveolar bone) by attaching collagen fibres to the cementum.
- This has a very fast turnover.

Cementum is a calcified connective tissue covering the root of tooth.

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6
Q

What is the effect of vit C deficiency on teeth health

A

Vit c needed for synthesis of collagen so periodontal ligament rapid turnover not supported and teeth fall out.

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7
Q

What are the 3 papillae of the tongue

A

They are projections of the lamina propria

Fungiform - mushroom with 5 tastebuds each
Filiform - entire surface- no tastebuds but tactile receptors that increase friction
Valate - big, has moat and the most tastebuds, back of the tongue

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8
Q

Describe the 3 intrinsic muscles of the tongue

A

Longitudinal muscles cause shortening length of the tongue

The vertical muscles cause flattening of the tongue

The horizontal/ transverse muscles cause narrowing of the diameter of the tongue

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9
Q

What / Where are the 3 major salivary glands and which secretory cells do they have

A

Parotid : under the ear -Serous cells

Submandibular : mouth floor- mixed mucous and serous

Sublingual : underneath tongue: mostly mucous

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10
Q

Compare the composition and function of the serous cells secretion vs mucous cells secretion

A

Serous cells have dark staining granules of watery, enzyme rich secretion.

-Enzymes Amylase breaks down starchy debris around teeth and Lysozome kills bacteria

Whereas Mucous cells secrete a light staining viscous secretion which lubricates the food bolus.

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11
Q

What is the overall composition of saliva and what is the nerve stimulation for saliva secretion

A

Composition: water + mucus + enzymes

Stimulated by parasympathetic ANS by seeing, smelling, thinking about food

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12
Q

What are the 4 key roles of organs in the digestive system and where do they vary in along the gut tube

A

Digestion = chemical breakdown of ingested food into absorbable molecules. In the mouth, stomach, duodenum and small intestine. cecum by bacteria

Absorption= movement of nutrients from gut to blood/lymph. In the stomach (water ions drugs) DJ Ilieum, (majority) and large intestine

Secretion: saliva etc occurs along entire GI tract

Transport to do 1 and 2. occurs along entire GI tract

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13
Q

What are the 5 ways that secretion and transport occurring in the gut epithelium is increased by increasing SA ( from biggest to smallest modification)

A

Gross convolution: twisting to fit more tube in the same space

Luminal folds : Large circular folds, in intestines as plicae circularis or longitudinal rugae in stomach (core of submucosa, covering mucosa)

Projections toward the lumen (ie villus- core of lamina propria covering epithelium- microvilli core of cytoplasm)

Projections away from the lumen (ie glands)

Having more time: increases the amount of food can absorb

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14
Q

List the 4 layers of the gut tunic from the lumen to deep

A

Mucosa (mucous membrane)

Submucosa

Muscularis externa (external smooth muscle)

Serosa (visceral peritoneum or adventitia)

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15
Q

Describe the tissue component and function of Mucosa

A

Closest to the lumen is the epithelium for (secretion, absorption and/or protection)

Underneath is the Lamina Propria: a soft bed of loose connective tissue that carries nerves, capillaries and have defense cells.

Muscularis Mucosa: double layered smooth muscle (inner circular, outer longitudinal) that provides independent movement of mucosa from the external muscle coat.

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16
Q

Describe the tissue component and function of Submucosa

A

This is a Thick bed of loose connective tissue that carries larger bv, lymphatic vessels and nerves (eg. submucosal plexus for mucose and submucosa).
Function is to connect the mucosa to external muscle but allows some movement between the two.

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17
Q

Describe the tissue component and function of Muscularis externa

A

Two layers of smooth muscle :
1. An inner layer of circular muscle
2. an outer layer of longitudinal muscle
Work together to produce peristalsis and coordinated by the myenteric nerve plexus that occurs between the two muscle layers

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18
Q

What Nervous system controls the plexes in the 4 layers of the gut tube and what are its interactions with the ANS

A

The enteric nervous system controls the submucosal and myenteric nerve plexus and is stimuated by the parasympathetic nerve system of the ANS and inhibited by the sympathetic nerve system

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19
Q

Describe the tissue component and function of Serosa

A

This is the slippery outer covering of the gut tube made of connective tissue and then outermost layer of mesothelial cells that secrete serous fluid. (visceral peritoneum) if the structure is in contact with the body cavity.
For the oesophagus, the outermost connective tissue layer is the adventitia (organ next to organ).

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20
Q

What is the general appearance/location of the oesophagus

A

It is a 25cm long muscular tube from the pharynx to the stomach. Dorsal to the trachea. Has collapsed lumen when empty which stretches to accomodate food

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21
Q

What are the major functions of the oesophagus and what major differences in the oesophagus tunic layers reflect this

A

Function:
1. Protection: Epithelium:
This is stratified squamous epithelium for protection against abrasive fragments of food.
-gets regenerated by basal layers, renewed each week

  1. Transport: Has an additional layer to smooth muscle of skeletal muscle in the upper third of the oesophagus to allow rapid contraction and voluntary swallowing.
    - – Has a fibrous adventitia which attaches it to trachea etc
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22
Q

Describe the general structure of the stomach including 4 regions

A

J shaped bag with 1.5 litre capacity.
Has 4 regions:
1. Cardia: Entrance containing Mostly mucous glands
2. Fundus (top above cardia) and
3. Body : (main section) that both secrete acid, enzymes and mucous
4. Pylorus Exit with mostly mucous glands.

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23
Q

What are the interesting muscle features of the stomach (not related to differences in the tunic)

A

There is an thickening of the internal circular smooth muscle at the exit of the stomach called the Pyloric sphincter. This controls the rate and volume of chyme exiting.
The walls are also lined with transient longitudinal folds called rugae, only present when empty.

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24
Q

What are the major functions of the stomach and what major differences in the stomach tunic layers reflect this

A

Primary function is storage
Epithelium of mucosa form many pits lined with mucus secreting cells, and glastic glands which open into the gastric pits. This helps with the
1. Secretion of acid, enzymes and mucus making chyme

  1. Digestion of proteins by pepsin
  2. Absorption of water, ions, and some drugs
  3. Protection: against its own secretions and microbes
    There is the addition of an innermost oblique layer of smooth muscle to the Muscularis externa to generate mixing waves
  4. Transport
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25
Q

What are the cells in the gastric pit and neck of the stomach and what is their function

A

Surface mucous cells
-> they secrete insoluble alkaline mucus which protects the mucosa from acid and pepsin
Neck : Mucous neck cells : secrete soluble acid mucous at mealtimes

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26
Q

What are the cells in the gastric glands of the stomach (from lumen to base) and what is their function

A

Undifferentiated stem cells which divide to create new epithelium

Parietal cells that secrete H+ and Cl- to sterilise the food and acidify the environment –> allow activation of enzyme digesting protein. It also secretes intrinsic factor which is important for absorption of vit B12~ and therefore RBC haematopoesis.

Chief cells: secrete Pepsinogen and gastric lipase
Pepsinogen is converted into pepsin by the acid in the gland lumen.

Gastrin cells: release hormone gastrin into the blood stream which stimulates secretion of acid and pepsinogen, increases muscular contractions of the stomach and relaxes the pyloric sphincter

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27
Q

What stimulates gastrin cells and are they exocrine or enterendocrine

A

They are enteroendocrine and are stimulated by stomach distension and change in pH when you eat food

28
Q

What are the two cells of the gastric pit that produce products for digestion and how do they stop autodigestion

A

The parietal cells -produce the acid HCl and intrinsic factor. To stop autodigestion: secretes HCl as H+ and Cl- ions
The chief cells secrete pepsinogen and gastric lipase but it stop autodigestion: by secreting a precursor to the protein digesting Pepsin enzyme that is only activated in the lumen of the gland.
Also autodigestion is stopped by alkaline mucous of the surface mucous cells which protects from the acid and the pepsin

29
Q

List the main functions of the liver

A

Synthesis of bile salts for emulsifying lipids

Metabolism of carbs, protein and lipids (glycogen storage and release)

Phagocytosis of rbc, wbc and some bacteria.

Storage of vitamins/ minerals+ activation of vit D

detoxifying drugs

30
Q

What cells carry out the functions of the liver and what do they require to do this

A

Hepatocyte which are the epithelial cells from embryonic endoderm do all the functions.
They require:
1. access to nutrient laden blood drained from the intestinal wall
2. access to oxygenated blood from the systemic circuit
3. Access to ducts which drain bile to the gall bladder

31
Q

How are the hepatocytes placed in relation to the blood spaces around them

A

Hepatocytes are arranged in lins (plates) extending from the central vein of the lobule. There are sinusoidal capillaries in between them and they are very dilated (>1 RBC) and leaky.

32
Q

What is between the hepatocyte and the blood in the sinusoidal capillaries (from hepatocyte side) and the function of these features

A

hepatocyte microvilli-> for increasing SA for transport,

The lymph space of Disse (contains filtered lymph)

Endothelial cell of the sinusoid–> fenestrated to exclude RBC from blood plasma

33
Q

How are the hepatocytes placed in relation to the bile spaces around them

A

The bile produced by the hepatocytes go to Bile canaliculi which are small tunnels between the tight junctions of neighbouring hepatocytes. The canaliculi lead to ductules, ducts and then common hepatic duct

34
Q

Describe the structure of a liver lobule

A

This is hexagonal stack of plates of hepatocytes, with a central vein in the centre and branches of the hepatic artery and hepatic portal vein on the outer border. These feed towards the central vein. However the bile produced by the hepatocytes will drain away from central vein into a tributary of the central duct on the outer border.

35
Q

What does the hepatic portal vein carry vs hepatic artery

A

Hepatic portal vein carries nutrient laden deoxygenated blood from the small intestine whereas hepatic artery carries oxygenated blood from the heart

36
Q

What is the outer border of the liver lobule containing the blood vessels and bile ducts called

A

portal area

37
Q

What connective tissue separates liver lobules

A

interlobular septum

38
Q

What is the exocrine function of the pancreas

A

The pancreas makes precursors of digestive enzymes (that digest proteins, carbs, lipids and nucleic acids) in secretes them in an alkaline juice which goes to the duodenum through a duct system

39
Q

What is the endocrine function of the pancreas

A

Has islets of langerhans which secrete insulin and glucagon for glucose homeostasis

40
Q

Is the spleen part of the digestive system

A

no

41
Q

describe the path of the pancreatic juice from point of secretion to the main pancreatic duct

A

It originates from serous type secretory cells arranged in a unit called Acinus (leaf) opening to an intercalated duct (twig). These join interlobular ducts (small branches) which lead to the trunk (main pancreatic duct).

42
Q

What is the order of things added to the duodenum for digestion and where do they come from

A

Chyme from the stomach connects directly through pyloric sphincter

Bile from the liver is either released into the common bile duct from the gall bladder where it has been concentrated or just straight from the liver

Pancreatic juice containing precursors go through the main pancreatic duct

43
Q

Describe the 3 regions of the small intestine describe the main function of the small intestine

A

Duodenum

Jejunum

Ileum
Main function is the most digestion and absorption. Its upper end (duodenum) also receives secretions from the liver, pancreas as well as the chyme from stomach

44
Q

What are the differences in the gut tunics for the small intestine

A

Mucosa: is specialised to greatly increase surface are available for secretion

Submucosa just downstream of the pyloric sphincter contains Glands of Brunner which secrete HCO3 rich mucous which neutralises acidic chyme and buffers to optimise pH for pancreatic enzymes.

45
Q

What are the modifications done to increase surface area in the small intestine (big to small)

A

Gross convolutions
Plicae (circular folds that are permanent wrinkles.

Each plica has a core of submucosa covered in mucosa

Villi (made of lamina propria covered by epithelium

Microvilli (extensions of cell membrane making the brush border on individual absorptive cells).

46
Q

What are the epithelial cells in the villus of the small intestine and what do they do

A

Columnar absorptive cells (enterocytes) which absorb the molecules from digestion

Goblet cells: that secrete mucus

47
Q

What are the epithelial cells in the intestinal glands mucosa of the small intestine and what do they do

A

Undifferentiated cells (for generating new epithelium)

Enteroendocrine cells: secrete hormone secretin into the capillaries of the lamina propria

Paneth cells: secrete bactericidal enzyme lysozyme and phagocytose

48
Q

Where are the digested carbohydrates, proteins, water and electrolytes transported compared to lipids

A

They go to venules in the submucosa which are tributaries of the hepatic portal veins.

The lipids are transported by the lymphatic vessel (also goes to the submucosa) in each villi which eventually drain into the venous system

49
Q

How are the epithelial cells on the villus of the small intestine replaced

A

Cell division occurs deep in the intestinal glands then the entire sheet (except Paneth cells) moves slowly up the gland walls and up the sides of the villi because old cells are shed from the tip.

50
Q

What stimulates the release of secretin from what cell and what does it do

A

Secretin release from enteroendocrine cells is stimulated by arrival of acid chyme. It stimulates the release of pancreatic juice. Cholecystokinin from the same cells is released in response to amino acids and also stimulates pancreatic juice + bile release.

51
Q

What is special about the lymph vessel in villus of the small intestine

A

They are lacteal- meaning that Lymph is milked by contraction of the smooth muscle which shorten the villus. These smooth muscle fibres are in the lamina propria and arise from the muscularis mucosae

52
Q

List the 7 regions of the large intestine

A

Cecum, Ascending colon, transverse colon, descending colon, Sigmoidal colon, rectum, anus

53
Q

What are the main functions of the large intestine

A

Absorption of salts and water (but still less than small intestine)

Conversion of chyme into feces with remaining carbs fermented by bacteria

Production of some vitamins B&K which are absorbed

Secretion of mucus to lubricate feces

Defecation

54
Q

What controls the flow of chyme from the ileum into the cecum

A

ileocecal valve

55
Q

What is the cecum structure and function

A

Dilated pouch containing Bacteria (not enzymes) for digestion. Humans have none for digestion of cellulose

56
Q

What is the structure and function of the appendix

A

Vestigal worm like appendage of the cecum which contains lymphatic tissues

57
Q

What is the final composition of feces

A

Bacteria 30%
Undigested dietary fibre 30%
Cells shed from the intestinal lining and mucus

58
Q

What is the colour of the feces from

A

the bacterial decomposition of bilirubin

59
Q

What are the special features about the Mucosa of the large intestine

A

No villi but many intestinal glands

surface epithelial cells that are enterocytes (absorptive)

intestinal glands containing mostly goblet cells but not paneth (no more digestion)

Many clusters of lymphocytes in the lamina propria

cell renewal like small intestine- replaced every 5 days

60
Q

What are the special features about the Muscularis externa of large intestine

A

The outer longitudinal muscle is thickened in three strips. The strips called tenae coli contract to pull the intestinal tube into sac like pockets called haustra coli. Haustra change shape and position

61
Q

Describe the cells found in the mucosa of the colon intestinal glands (lumen to deep)

A

Columnar absorptive cells (enterocytes) which are absorbing water

Goblet cell: secreting mucus to lubricate the passage of the faeces and increase in frequency as you approach the anus

Undifferentiated cells: stem cells to form new epithelium

White blood cells in the lamina propria - lymphocytes that provide defense against invading bacteria from the colon lumen

62
Q

What are the main causes of diarrhoea and therefore reverse is constipation

A

Too much intestinal motility : too much peristalsis so transmission time is reduced and not able to reabsorb

Enterocytes not functioning : unable to reabsorb water

Cholera toxin: locks G protein in active phase and results in excess up regulation of Cl- ion channels

Colon cancer causing removal of parts of the colon

63
Q

What is between the rectum and anus

A

2cm of anal canal that is closed by 2 sphincters. The inner collar is smooth muscle and outer is skeletal muscle

64
Q

What causes defecation

A

Stretching of the rectal wall intiates a reflex contraction of the teniae coli in the descending colon and rectum.
Shortening of this part of the gut tube increases pressure on the rectum and causes the internal sphincter to relax (open). The outer voluntary muscle will then be relaxed voluntarily or if cant defecate then it will stay in contracted state and the defecation reflex subsides

65
Q

What epithelium is in the anus

A

It changes from glandular epithelium to stratified squamous which is sacrificial

MEDSCI142 (9 decks)

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