Digestive system I Flashcards
What is galt?
GALT is gut associated lymphoid tissue and contains 70% of immune system and 25% of the intestine
mucosal mass.
how many layers of peritoneum and what are they?
2 layers and they are parietal and visceral
what is peritoneal cavity?
Peritoneal cavity is the space between the parietal and visceral layer and has lubricating serous fluid
What is greater omentum and it’s functions?
It is the largest fold of the peritoneum and drapes over transverse colon and the small intestines like an apron.
It has 4 layers and is a double sheet that folds back on itself.
Functions are:
* Stores fat: Contains adipose tissue
which can greatly expand with
weight gain — the beer belly.
* Has many lymph nodes containing
macrophages and plasma cells
(which produce antibodies) to
combat infections of the GIT.
What is lesser omentum?
It is the peritoneal fold that suspends the stomach and duodenum from the liver.
* Pathway for blood vessels
entering the liver.
* The lesser omentum contains
the hepatic portal vein, common
hepatic artery, common bile duct
and lymph nodes.
17.
What is Enteric Nervous System?
It is the brain of the gut and extends from the oesophagus to the anus. Contains 100 milion neurons more than spinal cord.
* Functions independently but regulated by the autonomic
nervous system:
What are two plexuses (networks) of Enteric Nervous System?
Myentric plexus
* This contains a network of sympathetic and
parasympathetic nerve fibres between the
circular and longitudinal muscles of the
muscularis.
* Controls strength and frequency
of muscle contraction: gut motility.
Submucosal Plexus
* Network of sympathetic and
parasympathetic nerve fibres within the
submucosa — controls digestive secretions
and detects sensory information.
What are the types of neurons in enteric nervous system?
-Motor neurons- outgoing action/signal
-Sensory neurons- incoming signal receive information
about the mucosal environment
- Interneurons- connects two plexus- myentric and submucosal
What is epiglottis?
a flap of elastic cartilage which
prevents food entering the trachea.
epi- = above
glottis = tongue
What does lower oesophageal sphincter do?
The lower oesophageal sphincter acts as a seal
on the stomach to prevent reflux of stomach
contents into the oesophagus.
What are the three types of exocrine cell found in stomach and what are it’s functions?
Parietal cells: Intrinsic factor
(IF).
* IF is needed for vitamin B12 absorption.
Hydrochloric
acid (HCl).
Secretes H+ and Clseparately; combining
in the stomach.
* HCl: Activates pepsin, acts as an anti- microbial agent, iron ingested is converted into a soluble form, assists in
activating bile and pancreatic juice flow.
* Vitamin B6 and zinc used to make HCl.
Chief cells: Pepsinogen- * Protein and lipid digestion.
Gastric lipase.
* HCl converts pepsinogen to the active enzyme pepsin (digests protein).
Goblet cells : Mucus
* Mucus protects against acid.
What are the functions of stomach?
- Mixing chamber — churns up food.
- Holding reservoir — storage.
- Defence — non-specific defence from gastric acidity.
- Absorption (limited) — water, alcohol, drugs, i.e. aspirin.
- Digestion — mechanical but also chemical
digestion of proteins and lipids. - Iron — made more soluble with stomach acid.
- Satiation — tells you to stop eating
The hormones found in stomach?
- Ghrelin — stimulates hunger.
- Gastrin (produced by G cells) — responds to
stomach distension. Stimulates gastric juice
secretion and gastric motility.
List pancreatic enzymes and their functions
Pancreatic amylase: Breaks down starches into sugars
Pancreatic lipase: Lipid / fat digestion.
Trypsin: Protein digestion
Chymotrypsin: Protein digestion
Ribonuclease: Digest RNA
Deoxyribonuclease: Digest DNA
What are the three regions of small intestine?
Duodenum - emulsification and most digestion
occurs here (30cm).
Jejunem - most absorption occurs here (2.5m)
Illeum - vitamin B12 is absorbed (3.5m).
What is brush border enzyme?
- Enzymes attached to the intestinal
lining (not free in the lumen). - Include maltase, sucrase, lactase.
- Hence enzymatic digestion occurs
on absorptive cell surface. Release
when cells slough off.
What is cholecystokinin (CCK)?
Cholecystokinin (CCK) is a peptide hormone
that is secreted by enteroendrocrine cells
in the duodenum (small intestine). * CCK is released in response to high fat or
protein chyme entering the duodenum.
CCK performs the following functions: * Stimulates the pancreas to secrete
pancreatic enzymes (and hence
digest fat / protein / carbohydrates).
* Increases hepatic production of bile
and stimulates contraction of the
gall bladder (bile
à fat digestion).
* Mediates satiety (feeling of fullness).
Functions of small intestine
Functions:
* Movement / peristalsis of food.
* Digestion.
* Absorption of nutrients and
water.
* Hunger / satiety.
* Immunity — Peyer’s patches
and bacterial microflora.
What valve allows the flow of materials from the small to large intestine?
The ileocaecal valve allows one-way flow
of materials from the small to large intestine.
This valve can become faulty, allowing
large intestine microbes to overpopulate
in the small intestine (SIBO).
What are the four regions of large intestine?
Four regions:
1. Caecum — appendix is attached —
a twisted tube about 8cm in
length. Part of our immune
system: Contains macrophages,
lymphocytes, bacteria.
2. Colon — ascending, transverse,
descending regions.
3. Rectum.
4. Anal canal — mucous membrane
folds. Contains an internal and
external anal sphincter.
What cells remove foreign bodies from the cell?
Kupffer cells are phagocytic cells which
remove foreign bodies from the blood
(they are a type of white blood cell that
specialise in engulfing microbes).
What is hepatic first pass?
Hepatic first pass: All blood from the
GIT is transported to the liver (via the
portal vein) to be filtered / metabolised
before entering systemic circulation.
What are the functions of the liver?
- Cleansing blood of microbes.
- Detoxification — metabolising drugs, toxins, alcohol.
- Bile production and secretion.
- Haemolysis (Kupffer cells)
- Synthesis of plasma proteins — blood clotting and coagulation
factors. - Hormone homeostasis — deactivating all hormones.
- Metabolism of glucose (glycogen), fats (hepatocytes store
triglycerides) and amino acids. - Heat production — thermogenesis.
- Synthesis — vitamin A (from beta carotene), CoQ10 and
activation of vitamin D.
10.Storage — vitamins (A,D,E,K, B12), iron, copper, glycogen.
What are the major types of liver detoxification?
Two major classifications of chemical compounds:
1. Hydrophilic: Excreted in urine or bile.
2. Lipophilic: Must be chemically altered into
hydrophilic compounds to facilitate elimination
