BBS2041 cases Iris Donker
BBS2041 Human Intermediary Metabolism
Cases
1
,BBS2041 cases Iris Donker
Index
Case Page
Case 1: GI tract – “Faecal characteristics teach us a lot” 3
Case 2: Energy production – “Fuelling the human body” 18
Case 3: Fasting – “A survival holiday” 32
Case 4: Exercise – “The physiology of champions” 39
Case 5: Amino acid metabolism – “A pleasant way of body reinforcement” 48
Case 6: Vitamin B12 – “A steak a day keeps the doctor away?” 54
Case 7: Iron – “Iron: the magic bullet?” 67
Case 8: Energy expenditure – “Body composition and energy expenditure” 75
Also includes: Lecture 05: Principals of human energy metabolism + Practical 3:
Body composition
Case 9: Alcohol – “Alcohol: friend or foe?” 84
This summary is of course not a guarantee that you will pass the exam, but it will certainly guide you
in the right direction :)
If you have any questions or remarks don’t fear to shoot me a message!
2
,BBS2041 cases Iris Donker
Case 1 GI tract
Physiology of the GI tract
Anatomy of the digestive system
• Oral cavity
o Receptacle for food
o First stages of digestion begins → chewing and secreting
saliva, containing enzymes, by the 3 pairs of salivary glands:
▪ Sublingual glands (Under the tongue)
▪ Submandibular glands (under the mandible
(jawbone))
▪ Parotid glands (near the hinge of the jaw)
o The saliva contains amylase for carbohydrate digestion and lipase for fat digestion.
(digestion and the enzymes playing a role will be described more elaborately in the 3rd LG
about digestion).
o Stratified squamous cells
• Esophagus
o Narrow tube that travels though the thorax to the abdomen.
o Wall: 1/3 skeletal muscle → transition to 2/3 smooth muscle
• Stomach
o Just below the diaphragm the transition
between esophagus and stomach is.
o Bag-like organ that can hold as much as 2
litres of fluid when fully expanded.
o 3 sections:
▪ Upper fundus
▪ Central body
▪ Lower antrum
o Stomach continues digestion by mixing food
with acid and enzymes (HCl, pepsin, lipase)
to create chyme.
o Pylorus (gatekeeper)
▪ The opening between the stomach and small intestine and is guarded by the
pyloric valve (thickened band of smooth muscle that relaxes to allow only small
amounts of chyme into the small intestine at any one time).
▪ Integrated signals and feedback loops between the intestine and stomach
regulate the rate at which chyme enters the duodenum.
o Simple columnar epithelium
• Small intestine
o This is where most digestion takes place
o 3 sections:
▪ Duodenum
▪ Jejunum
3
, BBS2041 cases Iris Donker
▪ Ileum
o Digestion is carried out by intestinal enzymes (amylase, lipase, trypsin, chymotrypsin),
aided by exocrine secretions from two accessory glandular organs which enter the initial
part of the duodenum through ducts
▪ Pancreas + Liver → Sphincter of Oddi (tonically contracted) keeps pancreatic
fluid and bile from entering the small intestine except during a meal
o Nearly all digested nutrients and secreted fluids are absorbed in the small intestine. →
1.5L of chyme passes into the large intestine.
o Columnar epithelium
• Large intestine
o Colon (proximal part of large intestine) → watery
chyme is converted into semisolid feces as water and
electrolytes are absorbed out of the chyme and into
the ECF.
o Rectum (terminal part of large intestine) → distension
of the rectal wall triggers a defecation reflex.
• Anus → through where feces leave the GI tract
o Has an external anal sphincter of skeletal muscle
(voluntary control).
Gut = stomach until anus
Wall structure GI tract and stomach
The basic structure of the GI wall is similar in the stomach and intestines, although variations exist
from one section of the GI to another
1. Mucosa
o faces the lumen
o Consists of:
▪ Single layer of epithelial cells
- The most variable feature per section in the GI tract
a. Transporting epithelial cells (enterocytes in small intestine)
b. Endocrine cells
c. Exocrine cells
d. Stem cells
- Cell-to-cell junctions between these epithelial cells differ in GI
a. Stomach and colon → very tight
4
BBS2041 Human Intermediary Metabolism
Cases
1
,BBS2041 cases Iris Donker
Index
Case Page
Case 1: GI tract – “Faecal characteristics teach us a lot” 3
Case 2: Energy production – “Fuelling the human body” 18
Case 3: Fasting – “A survival holiday” 32
Case 4: Exercise – “The physiology of champions” 39
Case 5: Amino acid metabolism – “A pleasant way of body reinforcement” 48
Case 6: Vitamin B12 – “A steak a day keeps the doctor away?” 54
Case 7: Iron – “Iron: the magic bullet?” 67
Case 8: Energy expenditure – “Body composition and energy expenditure” 75
Also includes: Lecture 05: Principals of human energy metabolism + Practical 3:
Body composition
Case 9: Alcohol – “Alcohol: friend or foe?” 84
This summary is of course not a guarantee that you will pass the exam, but it will certainly guide you
in the right direction :)
If you have any questions or remarks don’t fear to shoot me a message!
2
,BBS2041 cases Iris Donker
Case 1 GI tract
Physiology of the GI tract
Anatomy of the digestive system
• Oral cavity
o Receptacle for food
o First stages of digestion begins → chewing and secreting
saliva, containing enzymes, by the 3 pairs of salivary glands:
▪ Sublingual glands (Under the tongue)
▪ Submandibular glands (under the mandible
(jawbone))
▪ Parotid glands (near the hinge of the jaw)
o The saliva contains amylase for carbohydrate digestion and lipase for fat digestion.
(digestion and the enzymes playing a role will be described more elaborately in the 3rd LG
about digestion).
o Stratified squamous cells
• Esophagus
o Narrow tube that travels though the thorax to the abdomen.
o Wall: 1/3 skeletal muscle → transition to 2/3 smooth muscle
• Stomach
o Just below the diaphragm the transition
between esophagus and stomach is.
o Bag-like organ that can hold as much as 2
litres of fluid when fully expanded.
o 3 sections:
▪ Upper fundus
▪ Central body
▪ Lower antrum
o Stomach continues digestion by mixing food
with acid and enzymes (HCl, pepsin, lipase)
to create chyme.
o Pylorus (gatekeeper)
▪ The opening between the stomach and small intestine and is guarded by the
pyloric valve (thickened band of smooth muscle that relaxes to allow only small
amounts of chyme into the small intestine at any one time).
▪ Integrated signals and feedback loops between the intestine and stomach
regulate the rate at which chyme enters the duodenum.
o Simple columnar epithelium
• Small intestine
o This is where most digestion takes place
o 3 sections:
▪ Duodenum
▪ Jejunum
3
, BBS2041 cases Iris Donker
▪ Ileum
o Digestion is carried out by intestinal enzymes (amylase, lipase, trypsin, chymotrypsin),
aided by exocrine secretions from two accessory glandular organs which enter the initial
part of the duodenum through ducts
▪ Pancreas + Liver → Sphincter of Oddi (tonically contracted) keeps pancreatic
fluid and bile from entering the small intestine except during a meal
o Nearly all digested nutrients and secreted fluids are absorbed in the small intestine. →
1.5L of chyme passes into the large intestine.
o Columnar epithelium
• Large intestine
o Colon (proximal part of large intestine) → watery
chyme is converted into semisolid feces as water and
electrolytes are absorbed out of the chyme and into
the ECF.
o Rectum (terminal part of large intestine) → distension
of the rectal wall triggers a defecation reflex.
• Anus → through where feces leave the GI tract
o Has an external anal sphincter of skeletal muscle
(voluntary control).
Gut = stomach until anus
Wall structure GI tract and stomach
The basic structure of the GI wall is similar in the stomach and intestines, although variations exist
from one section of the GI to another
1. Mucosa
o faces the lumen
o Consists of:
▪ Single layer of epithelial cells
- The most variable feature per section in the GI tract
a. Transporting epithelial cells (enterocytes in small intestine)
b. Endocrine cells
c. Exocrine cells
d. Stem cells
- Cell-to-cell junctions between these epithelial cells differ in GI
a. Stomach and colon → very tight
4
