GI

Question 1

What are the 4 functions of the GI tract

Answer 1

Digestion, Secretion, Absorption, and Motility

Question 2

Structure of the GI tract wall

Answer 2

Apical layer is the Mucosa, then submucosa, then muscularis externa, then serosa

Question 3

Layers of the Mucosa

Answer 3

Epithelium, lamina propria, muscularis muscoa

Question 4

Function of lamina propria

Answer 4

Connective tissue through which small blood vessels, lymphatic vessels, and nerve fibers pass

Question 5

Function of Muscularis Mucosa

Answer 5

Smooth muscle involved in movement of villi

Question 6

What is the submucosa

Answer 6

It is the second connective tissue layer. Blood and lymph vessels that have branches that penetrate into BOTH the mucosa above and the muscularis externa below.
Also contains submucosal plexus - Network of neurons that innervate both the Muscosa and Muscularis Externa.

Question 7

Describe muscularis externa

Answer 7

3 layers- the circular muscles, myenteric plexus, and the longitudinal muscle. These smooth muscles provide the forces for mixing and moving the GI content. The Myenteric plexus is innervated by ANS, have nerve fibers that project to submucosal plexus

Question 8

Serosa

Answer 8

Thin layer of connective tissue that connects to Abdominal Cavity via thin sheets of connective tissue.

Question 9

Goblet Cells

Answer 9

Interspersed between epithelial cells and secretes mucus

Question 10

How is fat absorbed?

Answer 10

Blind-ended lymph vessels called LACTEALS - Eventually enters bloods through the thoracic duct

Question 11

Digestion by numbers

Answer 11

Amount of fluid ingested - 1200 mL, FLUID SECRETIONS BY GI 7000 Ml, AMOUNT EXCRETED IN FECES 100ML

Question 12

Carb absorption

Answer 12

250-300g - 2/3 starch rest lactose and sucrose
some digested by salivary amylase most digested by pancreatic amylaseto produce maltose and glucose polymers. Sucose and Lactose is only ingested
Sucrose Lactose and Maltose as well as well as slightly bigger polymers are broken down into monosaccharides by enzymes on brushborder

Question 13

How is Fructose Absorbed

Answer 13

Facilitated diffusion via glucose transporters to both enter and leave epithelial cell

Question 14

How is glucose absorbed

Answer 14

BY SECONDARY ATIVE TRANSPORT COUPLED WITH Na-Glu transporter
SGLT -
Leaves cell by GLUT

Question 15

Proteins

Answer 15

60-90g/d
Digested by pepsin and pancreatic enzymes - trypsin and chymotrypsin
Peptide fragments can be broken at carboxyl terminal via pancreatic enzymes and at amino terminal at the brushborder
Di and Tri peptides are brought into the cell via secondary active transport coupled with H - peptide transproters
Specified transporter for each amino acid bring them in via Na- AA transporter
Small Peptides exit basolateral side via facilitated diffusion transporters.

Question 16

How is fat absorbed

Answer 16

70-100g/d
Mostly digested by pancreatic lipase which breaks triglycerides to 2 free fatty acids and one monoglyceride
Fats must be emulsified
Diffused into the cell - Reporm to triglycerides in ER - aggregate and coated with amphipathic molecule.
After being processed by Golgi they are relased into interstitial fluid, called Chylomicrons

Question 17

Requirements for emulsification

Answer 17

Mechanical disruption of large droplets into smaller droplets
An emulsifying agent such as phospholipids and bile salts secreted in bile

Question 18

Form of fat that enters interstitial fluid from epithelial cells that synthesize the triglycerides

Answer 18

Chylomicrons - They are passed into lacteals

Question 19

Fat soluble vitamins

Answer 19

A D E K

Question 20

How are vitamin solublevitamins absorbed

Answer 20

Diffusion or mediated transport

Question 21

How is B12 absorbed

Answer 21

Must bind to intrinsic factor made by parietal cells in stomach

Question 22

Malabsorption

Answer 22

Decrease in ability to absorb fat soluble vitamins

Question 23

Celiac disease

Answer 23

Autoimmune mediated loss of intestinal surface due to sensitivity of wheat proteins known as gluten

Question 24

Pernicious anemia

Answer 24

Defficiency of b12 causes anemia - Caused by failure to produce intrinsic factor due to autoimmune attack of parietal cells of stomach, loss of part of stomach or small intestine

Question 25

Most abundant substance in chyme

Answer 25

Water 8 L , 1.5L moves to large intestine, osmotic gradient established due to absorbed solutes that creates osmotic pressure to diffuse water into the celsl

Question 26

Iron

Answer 26

Has a carrier protein and a storage protein

Question 27

Regulations of gastrointestinal processes

Answer 27

Things that stimulate processing - Chyme acidity, osmoalrity, concentration, distention
Receptors are mechanoreceptors, chemoreceptors, osmoreceptors
Effectors are muscles in tract wall and exocrine glands

Question 28

Enteric Nervous system

Answer 28

Local autonomic nervous system
Myenteric plexus influences smooth muscle contraction
Submucosal plexus influences secretory activities
ANS also influences

Question 29

Short Reflexes - Receptors to plexuses to effector cells

Answer 29

Long reflexes- - Receptors to CNS and back