50. Gastrointestinal Physiology Flashcards
What are the four functions of the digestive system?
Digestion
Secretion
Absorption
Motility
Discuss the mucosal layers of the stomach?
(Mucosa)Epithelium- important
Lamina propria- connective tissue
Muscularis mucosae- smooth muscle
Submucosa- connective tissue
Muscularis externa- circular/longitudinal
Serosa/adventitia
Explain the nervous system of the gut?
Myenteric plexus- controls motility, constricts
Submucosal plexus- large neural network
What is found in the lamina propria?
Glands, bloods/lymph vessels
What is found in the submucosa?
Contains neurones
Explain the muscular layers of the GI tract
Inner-circular- constricts lumen outer layer- longitudinal muscle-shortens tube Inner oblique (stomach) churns stomach
Explain the nervous innervation of the gut?
Autonomic- long and short enteric nervous system
Parasympathetic- vagus nerve
Sympathetic- splanchnic nerve
What controls secretion and motility in the gut?
Parasympathetic increases secretion and increased motility
What are the different types of carbohydrates?
Monosacharides (hexose 6C sugars)
Disacharides- to monosacharides
Polysaccharides
Give examples of monosacharides
glucose
fructose
galactose
Give examples of disacharrides
Lactose- glucose and galactose
Sucrose- glucose and sucrose
Maltose- glucose and glucose
Give examples of polysaccharides
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.
What are the different ways that food can cross the membrane?
Transcellular
Paracellular
Vectorial transport
How is glucose transported into cells?
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
How is fructose transported into cells?
GLUT-5 transports fructose into the cells
GLUT-2 transports fructose out of the cells
What is the difference between proteins and peptides
Proteins- polymers of amino acids linked together by peptide bonds
Peptides- small proteins 3-10 amino acids in length= peptides
What enzymes are involved in protein digestion?
Proteases/Peptidase
What are the two ways proteins are digested?
Endopeptidases- cleave middle of proteins and splits in two
Exopeptidase- cleaves edges of proteins and makes amino acids.
How are amino acids transported across the membrane?
SAAT1 transporter-
this replaces the SGLT1 transporter and the process is the exact same as glucose
Explain the first part of dipeptide transportation (gut lumen to cell)
Dipeptide is pumped in via the PepT1 transporter (hydrogen also pumped in)
Hydrogen is then pumped out and sodium pumped in
Why is there an acid microclimate around the apical membrane
Due to acid constantly being pumped in and out
Explain the second part of dipeptide transportation
Sodium in and potassium out
No one knows how peptide gets out
