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Gastrointestinal System > Lecture 6.2: The Intestines > Flashcards

Lecture 6.2: The Intestines Flashcards

1
Q

What are the 3 parts of small intestine?

A

Duodenum
Jejunum
Ileum

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2
Q

How long is the Duodenum?

A

25cm

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3
Q

How long is the Jejunum?

A

2.5m

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4
Q

How long is the Ileum?

A

3.5m

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5
Q

What are the 4 parts of the large intestine?

A

Cecum
Ascending Colon
Transverse Colon
Descending Colon

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6
Q

Cells of the Mucosa (5)

A
  • Enterocytes
  • Goblet Cells
  • Paneth Cells
  • Stem Cells
  • Enteroendocrine Cells
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7
Q

What is the role of Enterocytes?

A

Absorption via microvilli (brush border)

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8
Q

What is the role of Goblet Cells?

A

Secrete mucus

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9
Q

What is the role of Paneth Cells?

A

Secrete defensins
Protect against infection and regulate the gut microflora

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10
Q

What is the role of Stem Cells?

A

Undifferentiated
New source of cells – turnover of cells~ 5days

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11
Q

What is the role of Enteroendocrine Cells?

A

In the crypts
Secrete a range of neuroactive compounds

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12
Q

Why are the 3 things intestinal motility is needed for to achieve?

A
  • Mixing of luminal contents
  • Ensuring that luminal contents contact with absorptive
    surfaces
  • Ensuring forward movement of luminal contents
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13
Q

What is Segmentation? What is its role?

A
  • Mixing and exposure to absorptive surfaces
  • A discontinuous, alternate contraction and relaxation
    of small intestine
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14
Q

What is Peristalsis? What is its role?

A
  • Propulsion of liminal contents towards the anus
  • Longitudinal followed shortly after by circular
    contraction, longitudinal relaxes before circular muscle
    – slow but steady wins the race!
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15
Q

Glucose then transported out of enterocyte via which GLUT transporter?

A

GLUT2

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16
Q

How is Fructose absorbed?

A

Via sodium independent facilitated diffusion via the GLUT5 carrier

17
Q

Uptake of amino acids and peptides, what transport systems have been identified? (5)

A
  • Neutral amino acids and methionine
  • Cationic amino acids (arginine, histidine, lysine)
  • Acidic amino acids (glutamate, aspartate)
  • Proline
  • Glycine
18
Q

In what part of the small intestine are protein products principally absorbed?

A

Duodenum and Jejunum

19
Q

How are lipids absorbed from the intestines?

A
  • Pancreatic lipase results in the production of
    monoglycerides and FFAs
  • These aggregate (with bile salts and phospholipids) to
    form micelles
  • The micellar core (non-polar) also contains cholesterol
    and fat soluble vitamins
  • Micelle ‘enters’ the brush border and contents diffuse
    passively into the enterocytes (bile salts remain
    outside – join the EHC)
  • Inside enterocytes TGs are reformed in the SER –
    aggregate to form chylomicrons
  • These leave via exocytosis and ultimately enter
    lacteals of villi which drain into venous circulation
19
Q

How are lipids absorbed from the intestines?

A
  • Pancreatic lipase results in the production of
    monoglycerides and FFAs
  • These aggregate (with bile salts and phospholipids) to
    form micelles
  • The micellar core (non-polar) also contains cholesterol
    and fat soluble vitamins
  • Micelle ‘enters’ the brush border and contents diffuse
    passively into the enterocytes (bile salts remain
    outside – join the EHC)
  • Inside enterocytes TGs are reformed in the SER –
    aggregate to form chylomicrons
  • These leave via exocytosis and ultimately enter lacteals
    of villi which drain into venous circulation
20
Q

What 2 oxidation states does iron exist in in the body?

A

Fe2+ (ferrous) and Fe3+ (ferric)

21
Q

What reduces reduces Fe3+ to Fe2+? What effect does this have?

A
  • Vitamin C
  • It is less likely to form insoluble complexes
22
Q

What reduces Fe3+ in the duodenum?

A

Reduced by the brush border enzyme ferric oxidoreductase

23
Q

Fe2+ is taken up via the …… transporter

A

DMT1

24
Q

How does iron leave the intestines?

A
  • Leaves via the basolateral transporter ferroportin
    (converted to Fe3+ and binds to transferrin in blood) * Removed from blood via RME
  • Binds to apoferritin to form ferritin
25
Q

What transporters facilitate calcium uptake in the intestines?

A

Enter down a concentration gradient via TRPV5 and TRPV6 channels

26
Q

How does calcium leave the intestines?

A
  • Inside, Ca2+ binds to calbindin
  • Moves to basolateral membrane and exists via a Ca2+
    ATPase pump (sodium-calcium exchanger NCX1,
    plasma membrane calcium exchanger PMCA1b)
27
Q

B12 is released from….by pancreatic proteases

A

Haptocorrin

28
Q

Poor absorption of vitamin B12 can be due to? (4)

A
  • Stomach damage
  • Autoimmune damage to secreting cells
  • Gastritis/peptic ulceration
  • Terminal ileum removed
29
Q

Effects of B12 malabsorption

A

Leads to Pernicious anaemia - Red cell production compromised

30
Q

What are Haustrations?

A

Small pouches caused by sacculation, which give the colon its segmented appearance

31
Q

Process of Defecation (7 Steps)

A
  • Stretch of the rectum initiates impulses in pelvic
    cholinergic nerves
  • These transferred to the sacral spinal cord
  • Subsequent transmission to higher centres allows the
    decision to defecate (or not)
  • This is done by voluntarily relaxing the external anal
    sphincter
  • The external anal sphincter is made of smooth muscle
    • this relaxes as a response to distension
  • Breathe in, closure of the glottis, increased
    intrathoracic and abdominal pressure
  • Relaxation of pelvic floor muscles – faeces expelled
32
Q

What is Transmural Inflammation?

A

Inflammation that causes the bowel wall to thicken and in some cases (but not all) the lumen to narrow

33
Q

What are Bowel Adhesions?

A

They are irregular bands of scar tissue that form between two structures that are normally not bound together

34
Q

What is the Erythrocyte Sedimentation Rate (ESR)?

A
  • An ESR is a blood test that that can show if you have
    inflammation in your body
  • If an ESR test shows that your red blood cells sink
    faster than normal, it may mean you have a medical
    condition causing inflammation

Gastrointestinal System (22 decks)

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