50. Gastrointestinal Physiology

Question 1

What are the four functions of the digestive system?

Answer 1

Digestion
Secretion
Absorption
Motility

Question 2

Discuss the mucosal layers of the stomach?

Answer 2

(Mucosa)Epithelium- important
Lamina propria- connective tissue
Muscularis mucosae- smooth muscle

Submucosa- connective tissue
Muscularis externa- circular/longitudinal
Serosa/adventitia

Question 3

Explain the nervous system of the gut?

Answer 3

Myenteric plexus- controls motility, constricts

Submucosal plexus- large neural network

Question 4

What is found in the lamina propria?

Answer 4

Glands, bloods/lymph vessels

Question 5

What is found in the submucosa?

Answer 5

Contains neurones

Question 6

Explain the muscular layers of the GI tract

Answer 6

Inner-circular- constricts lumen
outer layer- longitudinal muscle-shortens tube
Inner oblique (stomach) churns stomach

Question 7

Explain the nervous innervation of the gut?

Answer 7

Autonomic- long and short enteric nervous system
Parasympathetic- vagus nerve
Sympathetic- splanchnic nerve

Question 8

What controls secretion and motility in the gut?

Answer 8

Parasympathetic increases secretion and increased motility

Question 9

What are the different types of carbohydrates?

Answer 9

Monosacharides (hexose 6C sugars)
Disacharides- to monosacharides
Polysaccharides

Question 10

Give examples of monosacharides

Answer 10

glucose
fructose
galactose

Question 11

Give examples of disacharrides

Answer 11

Lactose- glucose and galactose
Sucrose- glucose and sucrose
Maltose- glucose and glucose

Question 12

Give examples of polysaccharides

Answer 12

Starch- glucose monomers linked by a a1,4 glycosidic bond.
Cellulose- glucose monomers linked by b1,4 glycosidic bonds.
Glycogen- glucose monomers linked by a a1,4 glycosidic bond.

Question 13

What are the different ways that food can cross the membrane?

Answer 13

Transcellular
Paracellular
Vectorial transport

Question 14

How is glucose transported into cells?

Answer 14

SGLT1 transporter used to transfer glucose and sodium into the cell

Glucose transported out of the cell by GLUT-2
Sodium transported out of cell as potassium transported in
water comes with sodium

Question 15

How is fructose transported into cells?

Answer 15

GLUT-5 transports fructose into the cells

GLUT-2 transports fructose out of the cells

Question 16

What is the difference between proteins and peptides

Answer 16

Proteins- polymers of amino acids linked together by peptide bonds

Peptides- small proteins 3-10 amino acids in length= peptides

Question 17

What enzymes are involved in protein digestion?

Answer 17

Proteases/Peptidase

Question 18

What are the two ways proteins are digested?

Answer 18

Endopeptidases- cleave middle of proteins and splits in two

Exopeptidase- cleaves edges of proteins and makes amino acids.

Question 19

How are amino acids transported across the membrane?

Answer 19

SAAT1 transporter-

this replaces the SGLT1 transporter and the process is the exact same as glucose

Question 20

Explain the first part of dipeptide transportation (gut lumen to cell)

Answer 20

Dipeptide is pumped in via the PepT1 transporter (hydrogen also pumped in)

Hydrogen is then pumped out and sodium pumped in

Question 21

Why is there an acid microclimate around the apical membrane

Answer 21

Due to acid constantly being pumped in and out

Question 22

Explain the second part of dipeptide transportation

Answer 22

Sodium in and potassium out

No one knows how peptide gets out