Anatomy, Histology and Control of GI tract

Question 1

what are the functions of the GI tract?

Answer 1

Secretion, digestion, absorption, motility, elimination, protection

Question 2

What is the GI tract?

Answer 2

continuous muscular digestive tube extends through thorax and abdomen

Question 3

What does GI tract do?

Answer 3

digest food mechanically and chemically into small molecules and absorbs the digested molecules through its lining into the blood

Question 4

What are the organs of the alimentary canal?

Answer 4

Mouth, pharynx, oesophagus, stomach, intestines - seperated by sphincters

Question 5

Where does large intestine terminate?

Answer 5

in anal canal

Question 6

What are accessory digestive organs?

Answer 6

Teeth, tongue, gallbladder, large digestive glands - salivary, liver and pancrease

Question 7

Where are the digestive glands and gallbladder?

Answer 7

in abdomen outside GI tract, connects via ducts

Question 8

What do accessory digestive glands produce?

Answer 8

variety of enzyme/fluid secretions contribute to breakdown of food stuff

Question 9

What is the basic structure of GI tract?

Answer 9

Serosa - muscularis externa - myenteric plexus - muscularis interna - submucosa plexus - submucosa

Question 10

What is shape of muscle in muscularis externa?

Answer 10

circular and longitudinal SM muscle

Question 11

Why does glandular mucosa stain dark?

Answer 11

Epithelial and CT nuclei it contracts

Question 12

Describe muscularis mucosa?

Answer 12

thin strip marks

Question 13

What does submucosa mainly contain?

Answer 13

Dense college fibres

Question 14

What does serosa have an edge of?

Answer 14

Mesothelium from near mesenteric attachment, adipose tissue and large blood vessels

Question 15

What local stimuli changes function of GI tract?

Answer 15

Stretch distension of tract wall
Concentration of solutes - osmolarity
acidity/alkaline PH
Concentration of nutrients - fats, peptides

Question 16

What does local stimuli act on?

Answer 16

Sensory receptors in mucosal layer of tract to initiate reflexes which act through muscles or glands

Question 17

What does signals from CNS change of GI function?

Answer 17

Anticipation of food, fear - not under voluntary control, performed by smooth muscles and glands

Question 18

What are 2 types of control on GI?

Answer 18

Nervous

Hormonal

Question 19

What is nervous control on GI?

Answer 19

Extrinsic - outside GI tract , via autonomic nerves from CNS - long reflexes
Intrinsic - solely within GI - via enteric nerves within plexuses - short reflexes

Question 20

What does parasympathetic nerves do on GI control?

Answer 20

Via vagus nerves, stimulate blood flow, motility, secretion, relaxes sphincters

Question 21

What does sympathetic nerves do on GI control?

Answer 21

inhibits blood flow, motility, secretion

contracts sphincters

Question 22

What does object in lumen do?

Answer 22

Activate sensory receptors of mucosa - send impulses to submucous plexes for secretions of fluid and mucus
Myenteric plexus - contract of muscles to push object

Question 23

Where are GI hormones secreted into?

Answer 23

Bloodstream

Question 24

Where are GI hormones produced?

Answer 24

By specialised cells called enterochromaffin cells spread through mucosal layer

Question 25

What do hormones produced do?

Answer 25

Regulate functions of tract itself or accessory organs - communicate with CNS

Question 26

What are the hormones?

Answer 26

peptides 20-40 AA in length

Question 27

How many peptide hormones in GI?

Answer 27

50 peptide hormones

Question 28

What does secretin do?

Answer 28

Secrete alkaline fluid from pancreas to duodenum