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Physiology and Pharmacology > Lecture 19 > Flashcards

Lecture 19 Flashcards

1
Q

What does the gastrointestinal tract (GI) provide?

A

Continual supply of water, electrolytes, vitamins and nutrients

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2
Q

How is the GI tract part of the outside world?

A

Secrete digestive juices (to digest the food)
Circulate blood around the tracts to carry away the products of digestion
Move food through the tract
Absorb water, vitamins, electrolytes and the products of digestion

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3
Q

How is the function of the GI tract controlled?

A

By local, nervous and humoral systems

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4
Q

What is the GI tract designed to do?

A

To smash up food both physically and chemically, so it may be absorbed together with water

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5
Q

What is the upper GI tract comprised of?

A

Buccal cavity (mouth), oropharynx/oesophagus, stomach , duodenum

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6
Q

What is the small intestine?

A

Duodenum, jejunum, ileum

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7
Q

What is the Lower GI tract comprised of?

A

Caecum, rectum, anal canal

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8
Q

What is the function of the buccal cavity?

A

Mechanical breakdown of food and mixes with saliva “soft bolus” - can be swallowed

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9
Q

What is the function of the oropharynx/oesophagus?

A

Conveys food from mouth to stomach

Upper sphincter controls entry into oesophagus

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10
Q

What is the function of the stomach?

A

Elastic bag that holds masticated food, adds gastric acid and digestive enzymes
Acts as a “hopper” where digestion started in mouth continues and it adds HCl and digestive enzymes
Squirts small amounts or “chyme” into the duodenum

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11
Q

What is the function of the duodenum?

A

First portion of small intestine
Bulk of digestion
Digestive enzymes and intestinal juice secreted
Most digestion of chyme occurs in the duodenum

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12
Q

What is the function of the jejunum and ileum?

A

Digestive enzymes from pancreas and liver enter via pancreatic duct
Pancreatic enzymes and bile from the gall bladder enter the small intestine in response to the hormone cholecystokinin, which is produced in the small intestine in response to the presence of nutrients

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13
Q

What is the function of the caecum?

A

Absorbs fluids and salts remaining after intestinal digestion
Mixes with mucus
The internal wall is composed of a thick mucous membrane, through which water and salts are absorbed

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14
Q

What is the function of the rectum?

A

Electrolytes/water absorbed (Na, K, Cl)
Feces thickened and mucus added
Indigestible food ingredients are decomposed by anaerobic bacteria

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15
Q

What is the function of the anal canal?

A

Continence organ
Regulates defecation
Lubricates and transmits feces from rectum to outside world
The stool is thickened through water absorption and mixed with mucus

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16
Q

How does mastication occur in the buccal cavity?

A

Teeth and tongue mechanically break down food and the addition of saliva results in a smooth soft bolus of food, lubricated and readily swallowed

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17
Q

What are the muscles involved in mastication?

A

Masseter, temporalis, pterygoids

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18
Q

What is the buccal cavity innervated by?

A

V3 of trigeminal nerve (cranial nerve V)

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19
Q

What does saliva contain?

A

Alpha-amylase which begins breaking down starches in the bolus
Some people have more than others

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20
Q

Where does digestion begin?

A

In the buccal cavity
Where food enters the alimentary canal
Bounded on the outside by the lips and on the inside the oropharynx

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21
Q

Where is the oesophagus located?

A

Conduit between oropharynx and stomach

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22
Q

How long is the fibromuscular tube?

A

20-25cm long

23
Q

Where does the oesophagus pass through?

A

Passes posterior to the trachea and the heart (left atrium) pierces the diaphram and enters the fundus of the stomach

24
Q

What layer of muscles is the oesophagus made up of?

A

Mucosa and submucosa

and connective tissue

25
Q

What do the muscular layers do in the oesophagus?

A

Preforms peristaltic movements to push the bolus of food down into the stomach
- Peristalsis can push food into stomach against gravity

26
Q

What leads to Hiatus hernia?

A

When fat shrinks

  • stomach herniates into thoracic cavity
  • leads to pain
27
Q

What is the structure of the stomach?

A

Bag-like, dilated section of the GI tract which can hold about 1 L of food

28
Q

Where is the stomach?

A

Lies in upper left of abdominal cavity, against the diaphram

29
Q

What does the stomach do?

A

Releases proteases and HCl, former begins smashing up proteins, the latter is bactercidal
- Proteases work in low pH’s hence HCl is necessary for normal functioning

30
Q

How often does the stomach churn its contents through peristalsis to produce chyme?

A

Every 40-60 mins

  • Fluid passes through stomach to duodenum quicker than food
  • Stops bacteria from proliferating too much
    • Acid activates various enzymes as well
31
Q

What is chyme?

A

Enzyme mixed with food

32
Q

Where does the duodenum receive chyme from?

A

Pylorus contracts to send food into duodenum

Feedback between pylorus and duodenum to keep food moving down the tract effectively

33
Q

What structure does the duodenum have?

A

25-38cm C-shaped structure lying adjacent to the stomach

34
Q

Does enzymatic breakdown occur in the duodenum?

A

yes

35
Q

What is the main function of the duodenum?

A

Regulates the control of stomach emptying via hormones, secretin and cholecystokinin
- pyloric sphincter is regulated by feedback reponses

36
Q

Where does most of the absorption occur?

A

At the jejunum

37
Q

What is the structure of the jejunum?

A

Inner surface consists of finger-like villi projections which increase the surface area of the jejunum allowing or greater absorption of nutrients

38
Q

What is the pH of the jejunum?

A

pH>=7

39
Q

What is the function of the villi of the jejunum?

A

“brush border” made up of microvilli

40
Q

Is nutrient transport across epithelial cells passive or active?

A

Passive for sugar fructose but active for amino acids, small peptides, vitamins and most glucose

41
Q

What is the pH for the stomach?

A

pH 1

42
Q

How different are the jejunum and ileum?

A

subtle

  • the diameter of its lumen is smaler and has thinner walls than the jejunum
  • has more fat inside the mesentery
43
Q

What is the structure specific to the ileum?

A

Abundant Peyer’s patches encapsulated lymphiod modules that contain large number of cells of the immune system

44
Q

What does ileum absorb?

A

Vitamin B12, bile ducts and products of digestion not absorbed by the jejunum?

45
Q

What are the three functions of the large intestine (colon)?

A

Absorb the remaining water and electrolytes from indigestible food matter
Accept and stores food remains that were not digested in the small intestine
Eliminate solid waste (feces) from the body

46
Q

What is the structure of caecum?

A

Pouch-like structure that is considerable to be the beginning of the large intestine

47
Q

How does the caecum receive chyme?

A

The ileum pushes chyme into it through the ileo-caecal valve

48
Q

Is there a difference in the structure of caecum between herbivores and carnivores?

A

Yes; larger in herbivores where cellulose-digesting bacteria are housed
Smaller or even absent in carnivores and replaced by the appendix

49
Q

What is the main function of the rectum?

A

Temporary store for feces

The final part of the large intestine connecting to the anus

50
Q

What is the structure of the rectum similar to?

A

Sacrum

51
Q

Where does the end of the rectum expand into?

A

Rectal ampulla where feces is stored before defecation

52
Q

What does the stretching of rectal walls stimulate?

A

Stretch receptors - desire to defecate

53
Q

What happens when voluntary retention of feces pushes it back into the colon?

A

More water is extracted, making it harder and may lead to constipation

Physiology and Pharmacology (27 decks)

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