Digestion

Question 1

The 6 main parts of the digestive tract?

Answer 1

Oral cavity
Pharynx
Oesophagus
Stomach
Small intestine
Large intestine

Question 2

Name the accessory organs?

Answer 2

Oral cavity: salivary glands - teeth - tongue

Small intestine: Liver - gall bladder - pancreas

Question 3

The 6 major functions of the digestive tract?

Answer 3

Ingestion + mastication
Propulsion + mixing (deglutition = swallowing)
Secretion
Digestion
Absorption
Elimination

Question 4

The 4 layers of the digestive tract, inside to out?

Answer 4

Mucosa
Submucosa
Muscularis
Serosa (or adventia)

Question 5

Describe the 3 layers of the Mucosa?

Answer 5

Inner mucous epithelium - Moist stratified squamous in the mouth, pharynx, oesophagus and anal canal
Simple columnar epithelium in the rest

Lamina Propria - Loose connective tissue

Muscularis Mucosae - Outer layer of smooth muscle

Question 6

What are mechanoreceptors + where are they located?

Answer 6

Specialised cells involved in peristaltic reflexes in the mucosa

Question 7

What are chemoreceptors + where are they located?

Answer 7

Specialised cells that detect the chemical composition of food in the mucosa

Question 8

How do serosa and adventitia vary?

Answer 8

Serosa is connective tissue with a surface that consists of mesothelium
Adventitia consists of ordinary connective tissue in the shape of fibers that rests around the organ that the tissue supports

Question 9

What is the ENS, where is it located and what does it contain?

Answer 9

The enteric nervous system, consists of the submucosal and myenteric plexuses

Question 10

What are proteins, carbs and fats broken down into?

Answer 10

Protein - amino acids
Carbs - monosaccharides
Fats - fatty acids + glycerol

Question 11

describe glycosidic bonds

alpha, beta, 1,4 etc.

Answer 11

Bonds between 2 monosaccharides, forms a disaccharide
condensation reaction involving loss of OH hydroxyl group of one molecule and loss of H in another

alpha glycosidic linkage is when the ‘1’ monosaccharide’s anomeric OH group is below the plane of the glucose string.

beta glycosidic linkage is when the ‘1’ monosaccharide’s anomeric carbon OH group is above the plane, causing a zig zag bond

1,4 etc is between the numbered carbons involved in the bond

Question 12

What enzyme can break 1,4 linkage between glucose molecules

Answer 12

alpha-amylase

Cannot break the 1,6 linkages (branches) of the starch

Question 13

disaccharides’ individual molecules?
Maltose
Sucrose
Lactose

Answer 13

maltose - 2 glucose (1,4 linkage)
sucrose - glucose + fructose (1,2 linkage)
lactose - glucose + galactose (beta 1,4 linkage)

Question 14

Triglyceride contains?

How would a double bond in the acid affect it?

Answer 14

Glycerol backbone and three fatty acid chains

In solid form, the carbons in the acid are saturated

a double bond in the acid would mean the triglyceride was liquid like olive oil

Question 15

What does an amino acid consist of?

Answer 15

Amino group - NH3+
Carboxyl group - COO-
R-group - varies with each amino acid
top H

Question 16

what does the stomach lining secrete, what do they do?

Answer 16

Parietal cells secrete HCl and chief cells secrete Pepsinogen

HCl converts pepsinogen to pepsin

Pepsin breaks down proteins

Question 17

How does the pancreas contribute to the digestive system?

Answer 17

Secretes pancreatic juice that contains enzymes and sodium bicarbonate that neutralises the acidic chyme

Question 18

what are chylomicrons?

Answer 18

carrier proteins that transport fats through lymphatic system
formed from proteins and phospholipids

Question 19

Describe carbohydrate digestion

Answer 19

salivary amylase breaks down polysaccharides into disaccharide maltose
pancreatic amylase in intestine also breaks down starch into disaccharides maltose, sucrose and lactose
intestines then break disaccharides down into glucose, fructose, and galactose with maltase, sucrase and lactase

Question 20

triglyceride + lipase = ?

Answer 20

monoglyceride and 2 fatty acids

Question 21

Describe fat digestion

Answer 21

fat is emulsified by bile from gall bladder, occurs in the duodenum

pancreatic + intestinal lipase digests the emulsified fats into monoglyceride and fatty acids

Question 22

describe protein digestion

Answer 22

pepsin in stomach breaks down protein to large polypeptides
trypsin and chymotrypsin from pancreas breaks down polypeptide into short peptides and amino acids
dipeptidase and aminopeptidase breaks these down into amino acids

Question 23

Why does the body emulsify fats?

Answer 23

to increase their surface area, aid digestion

after digestion, lipids interact with bile salts again to form water friendly micelles, enabling them to diffuse across the cell membrane and enter the cell

Question 24

What occurs after micelle formation in context of fat absorption?

Answer 24

the lipids enter the ER
reassembled into triglycerides
coated with chlyomicrons
carried into the body by lymph system