Digestion & Intestinal Absorption Flashcards

1
Q

Primary functions of digestive system

A
  • Digestion
  • Absorption
  • Secretion
  • Motility
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2
Q
  • Contain endocrine and exocrine cells
  • Detect nutrients and secrete hormones
  • Where nutrients absorbed
A

Epithelium

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3
Q
  • Loose connective tissue

- Provide support

A

Lavria Propria

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4
Q
  • Layer of smooth muscle

- Helps with motility

A

Muscularis Mucosa

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5
Q

Point at which CHOs and amino acids enter circulation

A

Blood and lymphatic vessels

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6
Q

Network of neurons for control of muscular activity

A

Submucosal plexus

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7
Q

Contraction narrows lumen

A

Circular muscle

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8
Q
  • Innervated autonomically

- Connected submuscal plexus

A

Myenteric externa

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9
Q

Contraction shortens tract

A

Longitudinal muscle

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10
Q

Mucosa

A
  • Epithelium
  • Lavria propria
  • Muscularis mucosa
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11
Q

Submucosa

A
  • Blood and lymphatic vessels

- Submucosal plexus

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12
Q

Muscularis Externa

A
  • Circular muscle
  • Myenteric externa
  • Longitudinal muscle
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13
Q
  • Connective tissue surrounding outer surface of tract

- Sheets of connective tissue connect it to abdominal wall and hold GI tract in place

A

Serosa

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14
Q

Gastrointestinal Wall

A
  • Mucosa
  • Submucosa
  • Muscularis externa
  • Serosa
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15
Q

Digestion phases

A
1 - Cephalic phase
2 - Mouth
3 - Saliva
4 - Pharynx
5 - Oesophagus
6 - Epiglottis
7 - Sphincters
8 - Peristalsis
9 - Stomach
10 - Small intestine
11 - Colon
12 - Rectum
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16
Q
  • Brain’s anticipation of food
  • Saliva production increases - parasympathetic
  • Stimulation of gastric juice secretion & insulin secretion
A

Cephalic phase

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17
Q
  • Mechanical breakdown
  • Mixing of food with saliva
  • Salivary amylase - CHO
  • Antibacterial action
A

Mouth

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18
Q
  • Bicarbonate - neutralise acid
  • Mucus - lubricates and protects from abrasion
  • Salivary amylase - CHO
  • Lysozyme - destroy bacteria
A

Saliva

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19
Q

Prevent aspiration into trachea

A

Epiglottis closes

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20
Q

Prevent air and stomach contents entering oesophagus

A

Sphincters at bottom of pharynx and opening to stomach

21
Q
  • Food moves towards stomach due to progressive muscular contraction
  • Compresses lumen and forces food along
A

Peristalsis

22
Q
  • Mechanical breakdown of food into chyme
  • Secretion of HCl - kill bacteria
  • Peptin begins protein digestion
  • Gastric lipase - digestion of fat
  • Temporary storage site
A

Stomach

23
Q
  • Chemical digestion all nutrients - pancreatic and brush border enzymes
  • Absorption of end-products, water, ions, vitamins
  • Secretion of hormones
  • Secretion of bicarbonate-rich fluid
A

Small intestine

24
Q
  • Absorption of ions and water
  • Transformation of chyme into faeces
  • Storage of faeces
A

Colon

25
Q

Pancreas

A
  • Secretion of pancreatic juice
  • Proteases
  • Pancreatic lipase
26
Q

Gall Bladder

A

Storage and concentration of bile

27
Q

Liver

A
  • Secretion of bile
    * Bile salts
    * Phospholipids
    * HCO3
  • Processing of absorbed nutrients
28
Q

Presence of CHO in GI tract is an important factor for insulin secretion

A

Incretin Effect

29
Q
  • Stimulated by nutrients in small intestine
  • Secreted by K cells in duodenum & jejunum
  • Stimulates insulin secretion
A

GIP

30
Q
  • Stimulated by nutrients in small intestine
  • Secreted by L cells in ileum
  • Promotes insulin release
  • Inhibits glucagon release
  • Delays gastric emptying
  • Suppresses appetite & energy intake
A

GLP-1

31
Q

Fat

A
  • 100,000 kcal
  • 12kg adipose tissue
  • 300g muscle triglyceride
  • 4.4g in blood
32
Q

Carbohydrate

A
  • > 3200 kcal
  • 350-700g muscle glycogen
  • 5g in blood as glucose and lactate
33
Q
  • Increases whole body utilisation
  • Maximum rate = 105g/h
  • Reduces gut discomfort
  • Improves performance
A

Sucrose

34
Q

Stomach

A
  • Mucus cells
  • Parletal cells
  • Chief cells
  • Enterochromaffin-like cells
  • D cells
35
Q

Alkaline solution released with mucus to protect stomach lining

A

Mucus cells

36
Q

Intrinsic factor necessary for Vitamin B12 absorption

A

Parletal cells

37
Q
  • Secretes pepsinogen

- Pepsinogen activated by acidic environment

A

Chief cells

38
Q

Release histamine to stimulate HCl secretion

A

Enterochromaffin-like cells

39
Q

Secrete somatostatin

A

D cells

40
Q
  • Secreted in gastric pit as pepsinogen
  • Activated by acidic environment
  • Breakdown proteins into 2-4 amino acids
  • Feedback loops prevent self-digestion
A

Activation of pepsin

41
Q
  • Stimulation by acetylcholine
  • Gastrin released, stimulates release of histamine, stimulates HCl production
  • When high HCl, somatostatin released. Inhibits histamine, ECL cell and G cell
  • Enterogastric reflex
    * Pylous detects food enters intestine
    * Stimulates negative feedback loop
A

HCl Production

42
Q

Fat digestion

A
1 - Emulsified
2 - Hydrolysed by lipase
3 - Temporarily stored as micelles
4 - Transported into epithelial cells
5 - Re-esterified to triglycerides
6 - Packaged as chylomicron
7 - Transferred into lymphatic system, then bloodstream
43
Q

Protein digestion

A

1 - Protein digested by pancreatic proteases & peptidases
2 - Small peptides absorbed via H dependent transport / amino acid enter via Na dependent transport protein
3 - Peptides broken down into amino acids
4 - Amino acids transported into blood

44
Q
  • Rhythmic contraction of longitudinal muscles
  • Greater mixing of material
  • Net flow through small intestine
A

Segmentation in small intestine

45
Q
  • Segmentation increased in ileum with gastric emptying

- After majority absorbed, peristalsis increases

A

Gastroileal reflex

46
Q
  • Moves undigested material to large intestine

- Prevents bacteria remaining too long

A

Migrating Myoelectric Complex (MMC)

47
Q

Small intestine motility

A
  • Segmentation
  • Gastroileal reflex
  • MMC
48
Q
  • Primary storage of material prior to defecation
  • Some digestion
  • Fluid absorption concentrates faetal matter
A

Large intestine

49
Q

Large intestine motility

A
  • Ileocecal sphincter
  • Segmentation
  • Intense contraction across transverse colon