Digestive System

Question 1

1.

what are the main parts of Digestive System

Answer 1

Oesophagus
Stomach
large intestine
Small intestine
Rectum

Question 2

what is a GI tract?

Answer 2

a long tube called Alimentary Canal which extends from mouth to anus. has about 30 feets length. opens at both ends for food to move during process.

Question 3

What are Accessory Structures?

Answer 3

They are not part of the GI tract but they help in food processing.
- Teeth
- Tongue
- Salivary glands
- Liver
- Gall bladder
- Pancreas

Question 4

How many layers does GI tract have?

Answer 4

4 in total
Mucosa
sub mucosa
muscularis propria
adventita

Question 5

how many layers does smooth muscle have?

Answer 5

2 layers known as Inner and outer longitudinal layer
helps with peristalsis - rhythmic contractions to allow food to move down through gut.

Question 6

Neural innervation system of the gut has how many systems?

Answer 6

2 systems :
Enteric Nervous system - Submucosal Plexus and Myenteric Plexus
Autonomic nervous system - Parasympathetic and Sympathetic

Question 7

What parts of body are involved in Mechanical Digestion?

Answer 7

Masticulation (chewing) food + saliva and forms a bolus.
teeth
tongue
salivary glands
lingual glands

Question 8

What about Chemical Digestion?

Answer 8

Salivary glands produce salivary amylase = catalyses the hydrolysis of starch into sugars

Lingual - enzyme in the tongue that helps triglycerides and other lipids turn into fatty acids and diglycerides.

Question 9

How are Gastric Secretions regulated in the digestive system?

Question 10

What is the process for Deglutition?

Answer 10

has 3 phases - Oral, Pharyngeal and Oesophageal phase.

Oral Phase –
food is getting prepared into pellets (food bolus) into a suitable size so it can be passed from the front of the mouth to back of the mouth and into the oropharynx.
From the pharynx, the tongue and other pharynx muscles moves the bolus further.
Soft palate moves and elevate voluntarily so the food doesn’t enter into the nose. Cranial nerves – Trigeminal, Facial and hypoglossal nerves are involved.
Pharyngeal Phase
When the bolus reaches the pharynx
- Special sensory receptors activate the involuntary part of the swallowing
- Reflex gets mediated by the swallowing centre in the medulla
- Reflex causes the food to be further pushed back into the pharynx and oesophagus done by rhythmic but involuntary contractions of many muscles in the back of the mouth, pharynx and oesophagus.
- Critical part of the pharyngeal phase includes the involuntary closure of the larynx by the epiglottis and vocal cords. And the temporary inhibition of breathing. This is done so food doesn’t go down the wrong pipe into the trachea and the lungs. Protects lungs from injury and irritation of the lung tissue.
Oesophageal Phase –
Food leaves Pharynx and joins the oesophagus which a tube like muscular structure leading to the stomach with the help of its rhythmic contractions. Oesophagus has 2 sphincters known as the Upper and lower whose job is to stop the food from regurgitate towards the mouth. Sphincters are basically acting as a physical barrier for food.

Question 11

What are the functions of Stomach?

Answer 11

secretes gastrin in blood
mixes saliva, food and gastric juice to form chyme
serves as reservoir for food before released into small intestine
Secretes gastric juice that has HCL so (it kills bacteria and denatures proteins), pepsis, intrinsic factor and gastric lipase

Question 12

what are the gastric glands and cell types in the stomach?

Answer 12

Gastric glands and Cell types in the stomach –
1. Surface mucous cell – secretes mucous
2. Mucous neck cell – secretes mucus

3. Parietal cells – secretes hydrochloric acid and intrinsic factor, needed for absorption of vitamins B12 which is then used in red blood cells formation or erythropoiesis. HCL helps to kill microbes in food, denatures the protein and converts the pepsinogen into pepsin.
4. Chief cell – secretes pepsinogen and gastrin lipase. Pepsin (activated form) is used to break down protein into peptides. Gastrin lipase splits triglycerides into fatty acids and monoglycerides.

Question 13

What is the role of Small intestine?

Answer 13

most digestion and absorption takes place here,
has circular fold - It increases the surface area for the digestion and absorption in the small intestine. Circular fold (plicae circulares).

Question 14

What is the role of Intestinal Juice?

Answer 14

Intestinal juice helps provide a vehicle for absorption of substances from chyme as they encounter the villi.

Question 15

What are brush border enzymes for?

Answer 15

• Found on the surface of microvilli of absorptive cells
• Break down the food products

Question 16

What is pancreas responsible for?

Answer 16

Pancreas is a gland that lies posterior to the stomach, produces enzymes that digest Carbs, protein, fats and nucleic acids.
- Produces Sodium bicarbonate which buffers the stomach acid (alkaline)
- Empties its contents into the duodenum

Question 17

What Functions are done by liver and Gallbladder ?

Answer 17

The liver makes up the bile which is important in the emulsification of fats.
Gallbladder stores the bile until its needed.

Question 18

How does Colon Function?

Answer 18

1. Peristalsis, Haustral Churning and mass peristalsis drive content of colon into the rectum
2. Bacteria in large intestine converts proteins into amino acids
3. Break down amino acids
4. Produce some vitamin B and Vitamin K
5. Absorption of some water, ions and vitamins
6. Formation of faeces
7. Defaecation (emptying rectum)

Question 19

How does Chemical Digestion take place in the colon?

Answer 19

The last stages of digestion happens through a bacterial action where substances are further broken down by the bacteria. Through this process some of the vitamins are synthesised.
Absorption – the colon absorbs water, electrolytes and some vitamins

Question 20

What does Faeces consist of?

Answer 20

• water
• inorganic salts
• sloughed off epithelial cells
• bacteria
• products of bacterial decomposition
• undigested portions of food.

Question 21

what happens in bacterial activity?

Answer 21

Lumen is involved in the bacterial activity where undigested carbs, proteins and amino acids are broken down into products that can be thrown in the faeces or absorbed and detoxified by the liver. Synthesises certain B vitamins and vitamin K.

Question 22

What is the process for Defaecation Reflex?

Answer 22

• The rectal walls swell up
• Stretch receptor sends sensory nerve impulses towards sacral spinal cord.
• Motor impulses travel back towards the descending colon, sigmoid colon and rectum and anus.
• Longitudinal rectal Muscles starts to contract, and the internal anal sphincter opens up.
• If the external anal sphincter is voluntarily relaxed, defecation occurs, and the faeces are expelled.