GI Structure

Question 1

Digestion Def

Answer 1

Mechanically and enzymatically breaking down food into simpler chemical components for absorption

Question 2

6 Digestive Processes

Answer 2

Ingestion (Voluntary), motility (peristalsis), mechanically (chewing, churning, mixing), chemically (enzymatic degredation), absorption/secretion (kidney) and defecation (voluntary)

Question 3

4 layers of intestine

Answer 3

Mucosa (innermost), submucosa, mucosa propria and serosa (outermost)

Question 4

Mucosa Outline

Answer 4

Innermost layer, surrounding lumen. Has 3 layers

Question 5

3 layers of mucosa

Answer 5

epithelium (innermost, function absorption), lamina propria (connective tissue, regulates epithelium) and muscularis mucosa (smooth muscle, controls local movement and optimises epithelium and lamina propria contact)

Question 6

Submucosa Outline

Answer 6

Connective tissue containing blood + lymph vessels (nutrient transport), nerve fibers (absorption and secretion) and lymphoid vessels (immune system)

Question 7

Muscularis Outline

Answer 7

Controlling intestinal motility (peristalsis and segmentation). 2 layers: inner circular and outer longitudinal. At different points the circular layer thickens and thins creating sphincters that control food passage

Question 8

Serosa Outline

Answer 8

Connective tough tissue lubricated in mucus. Prevents abrasive contact with other organs periodontal cavity via lubricants

Question 9

GI Tract Thickness (thinnest to thickest)

Answer 9

Small intestine, colon and esophagus. Esophagus thickness is useful for peristalsis

Question 10

Epithelium Outline

Answer 10

Innermost cell sheet (continuous). Transports nutrients and forms a protective barrier. Characterized by tight junctions and functional polarity. 4 types

Question 11

4 Types of Epithelial Cells

Answer 11

Enterocytes, Goblet Cells, Paneth and enteroendocrine

Question 12

Stratified squamous characteristics

Answer 12

Sectretes mucus (protects against abrasion + wear and tear). Found in eosophagus, mouth and anal canal

Question 13

Simple Columnar

Answer 13

Allow absorption and secretion to occur

Question 14

How does secretion/absorption occur with large molecules

Answer 14

Protein transporters. Substances transported include: amino acids, peptides, water, sugars, fatty acids, cholesterol, water soluble vitamins and ions. Activity controlled by hormones and nurotransmitters

Question 15

Epithelial Barrier Outline

Answer 15

Lipid. Only allows lipophilic molecules through, hydrophilic must pass through transporter proteins

Question 16

Epithelial Tight Junctions Outline

Answer 16

Proteins that anchor cells together towards luminal (apical) side, creates a strong barrier as cells are continuos. Comprised of occulin, claudin and junctional adhesion molecule. Permeability controlled by signalling proteins

Question 17

Functional Polarity Outline

Answer 17

The control of the rate of absorption/secretion. Protein channels respond to changes in the enviorment opening/closing

Question 18

Goblet Cells Function

Answer 18

Secret mucus. Prevents abrasion and pathogen contact with organ surface. Thickness varies in intestines

Question 19

Enteric Tear Mechanism

Answer 19

Colloquial: diahorrea. Removes pathogens without causing infection

Question 20

Paneth Cells Outline

Answer 20

Secrete alpha defensins, destroying pathogens in the small intestines

Question 21

Enterocytes Outline

Answer 21

Secrete beta defensins, in the colon

Question 22

Immune Cells in Lamina Propria

Answer 22

Mast cells, neutrophils, macrophages, monocytes and dendretic cells. Engulf and breakdown pathogens. Release cytokines to stimulate bigger immune response

Question 23

What causes coeliac disease, IBS and intolerences

Answer 23

Incorrectly regulated immuno-epethelial reactions (over active immune system)

Question 24

2 types of intestinal smooth tissue in muscarinic

Answer 24

Circular (controls segmentation mixing and peristalsis) and longitudinal (peristalsis)

Question 25

Enteric Nervous System Components

Answer 25

Submucosal plexus (regulating epithelial functions) and myenteric plexus (regulates smooth muscle contractions). Connected to CNS via autonomic nervous system fibres (sensory, motor and internuerons)

Question 26

Parasympathetic Gut Innervation Outline

Answer 26

Vagus (upper GIT) and pelvic (lower GIT) nerves carry signals from ganglia within myenteric and submucosal plexuses. Stimulate GIT

Question 27

Sympathetic Gut Innervation Outline

Answer 27

thoraco-lumbar spine region carries signal from synampse in ganglia within myelinic and submucosa plexuses. Inhibit epithelial transport and motility

Question 28

Enteroendocrine Cells Outline

Answer 28

Type of epithelial cell that sense changes in enviorment. Release paracrine (local) and endocrine (far acting) hormones

Question 29

G cells outline

Answer 29

enteroendocrine cells in stomach. Release gastrin = increase in pepsinogen/HCl = increased motility

Question 30

S cells Outline

Answer 30

Enteroendocrine cells in intestine. Release secretin in response to HCl in lumen = decreased gastrin= increased luminal HCO3- secretion

Question 31

I cell Outline

Answer 31

Enteroendocrine cells in duodenum. Release cholyecytocholeton in response to nutrient = bialiary secretions = incraese pancreatic secretions

Question 32

L cells outline

Answer 32

enteroendocrine cells in ileum and colon. Release GLP1 = increase insulin secretion

Question 33

Cephalic Pase Outline

Answer 33

Autonomic Nervous Cells. Salivary, Gatric and pancreayiovc secretions. Enetro nervouis nsystem relaxing mescles in GI and increasing secretions