Large Intestine

Question 1

What is the structure of the large intestine?

Answer 1

Four layered wall

Question 2

What is the function of the large intestine?

Answer 2

Absorption (water and electrolytes out of colon into blood volume
Defecation
DIgestion (b vitamins and vitamin K)

Question 3

What epithelium is the large intestine?

Answer 3

Stratified squamous epithelium

Question 4

How is the large intestine unique?

Answer 4

Chief parietal cells

Question 5

What is the enteric nerve supply of the large intestine?

Answer 5

Intrinsic nerves that supply the caecum -> anal canal
Consists of submucosal and myenteric plexuses

Question 6

What is the parasympathetic nervous supply of the large intestine?

Answer 6

CNX vagus until the left colic flexure
Pelvic splanchnic nerves S2-4 supply the remainder

Question 7

What is the sympathetic nervous supply of the large intestine?

Answer 7

Abdominopelvic splanchnic nerves T10-L2

Question 8

Is the large intestine supplied by visceral afferent fibres?

Answer 8

Yes

Question 9

What supplies the anal canal inferior to the pectinate line?

Answer 9

Somatic motor and sensory from pudendal nerve S2-S4
- Sensitive to pain, touch, temperature

Question 10

What is the digestive role of the large intestine?

Answer 10

Enteric bacteria ferment some indigestible carbohydrates and mucin (component of mucus)
Produces short-chain fatty acids (absorbed)
Fermentation also produces gases (-500ml/day) e.g. CH4 dimethyl sulfide
Bacteria also involved in vitamin synthesis e.g. B, K

Question 11

What is the role of the large intestine in absorption?

Answer 11

Most remaining water, electrolytes (largely NaCl) vitamins produced by bacteria

Question 12

What is the role of the large intestine in propulsion?

Answer 12

Haustral contractions and mass movement propel faeces towards rectum
Passage eased by mucous (globlet cells)

Question 13

What is the last role of the large intestine?

Answer 13

Defecation

Question 14

What is the arterial supply of the large intestine?

Answer 14

Branches of the superior mesenteric artery
- Caecum and appendix
- Ascending colon
- Part of the transverse colon
Branches of the inferior mesenteric artery
- Part of the transverse colon
- Descending, sigmoid, rectum

Question 15

What is the venus drainage of the large intestine?

Answer 15

70% via portal vein –> liver
Tributaries of the superior mesenteric vein
- Caecum and appendix
- Ascending and transverse colon
Tributaries of the inferior mesenteric vein -> splenic vein
- Descending, sigmoid colon, rectum

Question 16

What are varicose veins in the rectum referred to?

Answer 16

Haemorrhoids

Question 17

What are three features unique to the colon?

Answer 17

Teniae coli
- Longitudinal m. layer of the mscularis is arranged as three separate, thickened bands
- Extend from caecum to beginning of rectum
Haustra
- Muscular tone puckers colonic wall into pocket-like sacs called haustra (segmented appearance)
Omental (epiploic) appendices
- Small, fatty projections of the omentum that hang from the surface of the colin

Question 18

What type of mucosa is found in the large intestine?

Answer 18

Simple columnar epithelium

Question 19

What is the difference between large intestine and small intestine?

Answer 19

Large intestine does not have: circular folds, villi or brush border

Question 20

What does the large intestine have that the small intestine and stomach do not?

Answer 20

Goblet cells

Question 21

What is the role of goblet cells in the large intestine?

Answer 21

For protection against pathogens and helps faeces move through
Yellowy white and stringy

Question 22

What is special about the stomach?

Answer 22

Inner oblique layer

Question 23

What is special about the small intestine?

Answer 23

Villi and microvilli

Question 24

What is special about the large intestine?

Answer 24

Goblet cells

Question 25

What is dysbiosis?

Answer 25

Maladaptive imbalance of microbiome

Question 26

What is a microbiome?

Answer 26

Genetic material of all the cells in the microbiota

Question 27

What happens to the microbiota when the environment is too acidic?

Answer 27

Hard for biome to colonise in the stomach and small intestine

Question 28

What is the relationship of mother to baby during birth and breastfeeding in regards to microbiome?

Answer 28

Natural birth passes on mother's microbiome Breast milk = microbiome from mother = antibodies

Question 29

Where is the microbiome most abundant?

Answer 29

In large intestine

Question 30

What factors impact the ability of microbiota to have stable colonisation?

Answer 30

Acidic environments Bile Pancreatic juice Peristalsis

Question 31

What are factors that contribute to an individual's microbiota?

Answer 31

birth mother's health Birth vaginal/caesarean Infant milk Rural/urban living Diet Medications Stress levels Smoker

Question 32

What constitutes a health gut microbiome?

Answer 32

Diverse range of good bacteria Stability of microbiome = "good" bacteria keep "bad" bacteria in check Resistance to stress related change (e.g. antibiotic, infections)

Question 33

What vitamins are the gut microbiome important for digesting?

Answer 33

Synthesis of B vitamins and vitamin K

Question 34

What are the main roles of microbiota?

Answer 34

Synthesising vitamins Processing/digesting complex polysaccharides Synthesis of essential amino acids Glucose and cholesterol metabolism

Question 35

Why has research exploring the gut microbiome and health grown in recent years?

Answer 35

Increased availability and decreased costs of gene sequencing

Question 36

What diseases can be caused by disturbances/imbalances of the gut microbiome?

Answer 36

Inflammatory bowel disease IBS Diabetes RA/AS/Psoriatic arthritis