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Biomedicine > Lecture 7 - The Digestive System I > Flashcards

Lecture 7 - The Digestive System I Flashcards

1
Q

Expand on “You are what you eat”

A

You are what you digest
You are what you absorb
You are what you don’t excrete

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2
Q

Name 5 functions of saliva

A

DIGESTION - amylase
LUBRICATION
CLEANSING - of oral cavity & teeth
DEFENSE - presence of IgA & lysosomes
TASTE
BUFFER - for acidic foods (bicarbonate)
WASTE REMOVAL - eliminates urea/uric acid

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3
Q

What is the pH inside the stomach?

A

2 to 3

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4
Q

What prevents the contents of the stomach from refluxing into the oesophagus?

A

The lower oesophageal sphincter (aka the cardiac sphincter)

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5
Q

What are the six processes of digestion

A

1- Ingestion
2- Secretion - digestive juices
3- Mixing & propulsion - contraction, relaxation
4-Digestion - mechanical & chemical
5- Absorption - into blood & lymph
6- Elimination

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6
Q

What is the basic four-layer arrangement of tissues in the GIT?

A

1- Mucosa
2- Submucosa
3- Muscularis Externa
4- Serosa (peritoneum)

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7
Q

What is the GALT?

A

Mucosal-associated lymphoid tissue specifically found in the gut (hence Gut-Associated Lymphoid Tissue) makes up 25% of the intestinal mucosal mass and contains 70% of the body’s immune cells. It is a very important part of the body’s first line of defence.

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8
Q

What three layers comprise the Mucosa of the GIT?

A
  1. Epithelium
  2. Lamina Propria
  3. Muscularis Mucosa
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9
Q

What is MALT and where in the body can it be found?

A

Mucosal-Associated Lymphoid tissue which is a collection of immune cells and can be found in the Lamina Propria layer of the tonsils, oesophagus, small intestine, appendix, large intestine.

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10
Q

True or false: The peritoneum is the smallest serous membrane in the body

A

False

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11
Q

The peritoneum is supplied with many blood and ______ vessels and consists of a visceral and __________ layer. It provides a physical barrier to prevent local spread of __________.

A

lymph
parietal
infection

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12
Q

Define Ascites and name a possible cause

A

Ascites are an accumulation of fluid in the peritoneal cavity and could be caused by liver cirrhosis, heart failure, GIT malignancies, and pancreatitis.

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13
Q

Define Peritonitis and name two probable causes.

A

Peritonitis is an acute inflammation of the peritoneum and could be caused by bacterial infection, ruptured appendix, friction or surgical wounds.

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14
Q

What is the greater omentum?

A

It is the largest fold of the peritoneum which drapes over the transverse colon and small intestine like an apron. It stores adipose tissue (fat) and has many lymph nodes containing macrophages and plasma cells.

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15
Q

The lesser omentum is a pathway for _______ ________ entering the liver. It contains the hepatic _______ ____, common _______ artery, common ____ duct and lymph nodes.

A

blood vessels
portal vein
hepatic
bile

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16
Q

What is known as the ‘brain of the gut’?

A

The Enteric Nervous System

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17
Q

True or False: The Enteric Nervous System has only slightly fewer neurons than the spinal cord.

A

False. It has 100 million neurons - more than the spinal cord.

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18
Q

What regulatory effect does the Sympathetic Nervous system have on the Enteric Nervous System?

A

It decreases muscular activity (peristalsis) and glandular secretions

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19
Q

What are the two networks of the Enteric Nervous System called, where are they located and what is their function?

A
  1. Myenteric Plexus: sympathetic and parasympathetic nerve fibres located between the circular and longitudinal muscles of the muscularis. It controls the strength and frequency of muscle contraction (gut motility)
  2. Submucosal Plexus: The same two types of nerve fibres, situated within the submucosa which control digestive secretions and detect sensory information.
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20
Q

Name three accessory organs of the digestive system.

A

Salivary glands, pancreas, liver, gall bladder and biliary tract.

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21
Q

What percentage of the body’s immune system resides in the gut?

A

70%

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22
Q

What is the network of sympathetic and parasympathetic nerve fibres in the submucosa called and what does it control?

A

The submucosal plexus controls digestive secretions and detects sensory information.

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23
Q

What three types of neurons can be found in the enteric nervous system?

A

1- Motor neurons: in the myenteric plexus controls peristalsis and in the submucosal plexus controls secretions.
2- Sensory neurons: receive information about the mucosal environment (chemoreceptors and stretch receptors).
3- Interneurons: connects the two plexuses

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24
Q

Which parts of the digestive system contain skeletal muscle?

A

The mouth, pharynx, upper oesophagus and anal sphincter.

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25
Q

The vast majority of the GIT contains involuntary smooth muscle. What are the two layers that comprise this and what is their function?

A

The inner circular muscle and outer longitudinal muscle enable the mixing of food with digestive juices and propel food (bolus/chyme) through the digestive tract - peristalsis.

26
Q

What are Peyer’s patches and where can they be found?

A

Small masses of lymphatic tissue in the ileum region of the small intestine. They can be likened to the tonsils and their main function is the production of IgA.

27
Q

The GIT is supplied with arterial blood by branches of the abdominal _____, which includes the __________ arteries. Nutrient-rich blood is returned to circulation via the ______ system or directly from _____ veins.

A

aorta
mesenteric
portal
iliac

28
Q

What are the two sphincters of the stomach called and where are they situated?

A

The cardiac sphincter is at the top where the stomach meets the oesophagus, and the pyloric sphincter is at the bottom where it meets the duodenum.

29
Q

Name four functions of the oral cavity

A

Mastication
Speech
Taste
Swallowing

30
Q

Explain what is meant by peristalsis.

A

It is the wave of muscular contraction that propels food (bolus/chyme) along the digestive tract.

31
Q

How many teeth does an adult have?

A

32

32
Q

True or false: The parasympathetic nervous system stimulates the production of saliva

A

True

33
Q

Name two enzymes found in saliva and name the substances/cells they act on.

A

Amylase - Breaks down starches

Lysozomes - Breaks down bacterial cell walls

34
Q

How does the enteric nervous system in the stomach provide neural feedback?

A

Stretch receptors in the wall of the stomach get stimulated by food. Chemoreceptors monitor changes in pH. The activation of the submucosal plexus causes waves of peristalsis and gastric juice flow.

35
Q

What are the four main regions of the stomach?

A

The cardia, fundus, body and pyloric
{Stomach is a J-shaped organ; lesser and greater curvatures}

36
Q

Name the three types of exocrine cells in the stomach lining and the substances they secrete.

A

1- Parietal cells - Secretes Intrinsic Factor (for the absorption of Vit B12) and Hydrochloric acid (Activates Pepsinogen into Pepsin, acts as an anti-microbial, converts iron and calcium into more soluble form, activates bile and pancreatic juice flow)

2- Chief cells - Secretes Pepsinogen (protein digestion) and Gastric Lipase (fat digestion)

3- Goblet cells - Secretes mucus which protects the lining of the stomach from acid.

37
Q

Which hormones are secreted in the stomach?

A

Ghrelin, which stimulates hunger and Gastrin, which responds to stomach distention, stimulates gastric juice secretion and gastric motility (contractability).

38
Q

Describe the exocrine function of the pancreas

A

1.2 - 1.5l of clear Pancreatic juice is secreted into the duodenum every day. This consists of Sodium bicarbonate and water (to counter the acidity of chyme leaving the stomach), Protease enzymes for the digestion of proteins (Trypsin, chymotrypsin, ribonuclease, deoxyribonuclease), Pancreatic lipase for the digestion of fats, and Pancreatic amylase for the digestion of starches.

39
Q

What endocrine hormones are secreted into the blood by the pancreas?

A

Insulin, glucagon and somatostatin (growth-hormone-inhibiting hormone)

40
Q

How do the gallbladder and pancreas work together to enable digestion?

A

The gallbladder secretes bile, which breaks fats down into smaller particles, so that it can be acted upon by pancreatic lipase. Both of these secretions flow into the duodenum via the pancreatic duct and the common bile duct at the sphincter of Oddi.

41
Q

Bile is produced in the _____ by ___________ and stored in the ___________, which contracts to eject it when an individual has ingested ___.

A

liver
hepatocytes
gallbladder
fat

42
Q

Name three substances that can support and stimulate the gallbladder

A

Olive oil, curcumin and dandelion

43
Q

What can be done to correct low HCl in the stomach?

A

-Take Betaine HCl after the first bite of food
-Supplement Zinc, Vit B6 & B5
-Stimulate digestion all around through the use of digestive bitters or eating bitter greens at the start of a meal.

44
Q

Bile is composed of bile salts, ___________ and _________, which are formed mostly in the spleen.

A

cholesterol

bilirubin

45
Q

What is the ‘Ampulla of Vater’?

A

It is where the pancreatic duct and the common bile duct meet before entering the duodenum at the sphincter of Oddi

46
Q

Name the three parts of the small intestine and their main functions

A

1- Duodenum - The first 30cm of the small intestine where emulsification and digestion occurs
2- Jejunum - The next 2.5m where most of the absorption occurs
3- Ileum - The final 3.5m where Vitamin B12 is absorbed

47
Q

What are Villi and Microvilli and what is their most important function?

A

Villi are finger-like projections in the folds of the mucosal lining (formed by the muscularis mucosa) which contains lots of capillaries and lacteals (lymphatic capillaries). Microvilli are the tiny projections of each epithelial cell comprising the villi (known as the brush border). The main function of both is to increase the surface area of the small intestine in service to absorption.

48
Q

Brush border enzymes are attached to the __________ lining and include _______, _______ and _______, which break down sugars.

A

intestinal
maltase
sucrase
lactase

49
Q

Which brush border enzyme breaks down proteins?

A

Dipeptidase

50
Q

Which brush border enzymes break down DNA and RNA?

A

Nucleosidases and phosphatases

51
Q

The peptide hormone that is secreted by enteroendocrine cells in the duodenum in response to high fat or protein chyme.

A

Cholecystokinin (CCK)

52
Q

What percentage of absorption occurs in the small intestine?

A

90%

53
Q

What are Kupffer cells and where are they found?

A

They are phagocytic cells which remove foreign bodies from the blood and they are situated in the liver.

53
Q

Define detoxification

A

Detoxification is the process by which toxic substances are converted into non-toxic substances, allowing the body to excrete it

54
Q

True or False: The liver is the largest organ in the body

A

False.
It is the second largest, after the skin.

55
Q

Name 6 of the over 500 functions of the liver

A

1- Cleansing blood
2 - Detoxification
3- Bile production & storage
4- Haemolysis (Kupffer cells)
5- Synthesis of plasma proteins (blood clotting and coagulation factors)
6- Hormone homeostasis - deactivating all hormones
7- Metabolism of glucose, fats, amino acids
8- Heat production (thermogenesis)
9- Synthesis - Vit A, CoQ10 and Vit D activ.
10- Storage - Vitamins, Iron, copper, glycogen

56
Q

How does the liver metabolise

(a) carbohydrates
(b) fats
(c) proteins

A

(a) Excess glucose is converted into glycogen for storage and then converted back as needed
(b) Metabolises fat from storage as needed. Synthesises cholesterol and triglycerides
(c) Converts essential amino acids into non-essential amino acids. Removes nitrogen groups from amino acids to form urea for excretion. Breaks down nucleotides to form uric acid to be excreted.

57
Q

What are chylomicrons?

A

It is the molecule that is formed within the Golgi apparatus inside the small intestine epithelial cells from combining fatty globules with proteins, to then be absorbed into lacteals.

58
Q

Which enzymes are important in the Phase I transformation of lipophilic substances in the liver?

A

The CYP450 family of enzymes

59
Q

Why does liver detoxification require a good level of antioxidants?

A

Because lipophilic toxins are converted into more reactive substances in Phase I before being metabolised in the conjugation reactions of Phase II.

60
Q

What is a key anti-oxidant in Phase II liver detoxification?

A

Gluththione

Biomedicine (10 decks)

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