GHM L4 Flashcards
Describe the anatomy of the digestive system
- Mouth / oral cavity
- Tongue
- Salivary glands
- Pharnyx
- Spleen
- Stomach
- Liver
- Kidney
- Pancreas
- Small Intestine
- Large Intestine
- Gallbladder
- Anus
- Oesophagus
State the functions of the small intestine
- Completes digestion of food with aid of liver + pancreatic secretions
- Absorption of nutrients + minerals into body
Describe the structure of the small intestine
Ileum
Jejunum
Duodenum
Small intestine is long but due to muscle tone, is short in human stomach
What is “motility” in the small intestine?
Modes of contractions in the small intestine
- Segmentation
- Peristalsis
Describe segmentation
Mode of contraction found in small intestine, large intestine, predominates in small intestine
Non-adjescent alimentary tract organs contract + relax ALTERNATELY which allows this bidirectional movement of chyme
Bi-directional movement of chyme, for mixing not transport
Increases mixing + absorption
Involunary
Initiated by intrinsic pacemaker cells
Duodenum more active than ileum, slow propulsion
Describe peristalsis
Mode of contraction found in oesophagus, small intestine, large intestine + rectum
Contraction of circular + longitudinal smooth muscle in coordination to move chyme distally
Adjascent alimentary tract organs contract + relax alternately to move chyme distally along tract
Involuntary
Describe the functions of motilin
Motilin is released by duodenum + stimulates gastric emptying between meals
This stimulates peristaltic waves successively and distally
This leads to MCC - Migrating Motor Complex which is the “tummy rumble” - removal of indigestable food
MCC originates in stomach + duodenum
State the name of the valve between the small intestine and large intestine
Ileoceacal valve
State two factors which stimulate the opening of the ileoceacal valve
- Gastroileal REFLEX
- Gastrin secretion by parietal cells in stomach
(when terminal end of ileum under pressure)
What stimulates the release of motilin in the duodenum?
pH / change in pH
Describe how the small intestine is innervated
Sympathetic nerves:
- Splanchnic nerves
- Thoracic nerves
Parasympathetic Nerves:
- Vagus nerve
Describe how impulses are relayed in the small intestine
Impulses are relayed by
- Superior mesenteric plexus
- Celiac plexus
Describe what happens during parasympathetic excitation
Parasympathetic activation - rest & digest
- Increase digestive secretions, increase motility, increases salivation
- No sympathetic excitation
- Dilation of arteries in mesentery
Which artery supples blood to the small intestine
Superior mesenteric artery
Which veins drains blood from the small intestine
Superior mesenteric vein, which reaches the HEPATIC PORTAL SYSTEM
What factors increase blood flow to the intestines?
- Parasympathetic stimulation
- Feeding / taking in food
What factors constrict blood flow to the intestines?
- Sympathetic stimulation
What controls blood flow within the intestines?
- Glucose
- Local hormones
- Fatty acids
All REGULATED by ANS
State the function of the lesser omentum
Lesser omentum - attaches the liver to lesser curvature of stomach
What are the mesenteries of the abdominopelvic cavity?
- Greater omentum
- Transverse mesocolon
- Sigmoidal mesocolon
- Lesser omentum
- Mesentery
- Parietal peritoneum
- Visceral peritoneum
Describe the anatomy of the duodenum
Most short + straight section of small intestine
From pyloric sphincter to duodenal - jejunal junction
Retroperistoneal, static
Most active site of absorption
Connects to liver via lesser omentum
Connects to hepatopancreatic ampulla (bile duct + pancreatic duct)
C-shaped, wraps around pancreas
What is coeliac disease?
Disease of duodenum
Autoimmune disease
Caused by reaction to gliadin, a gluten protein
Involves tissue transglutaminase
State symptoms of coeliac disease
Grey, greasy, large stools
Anaemia, fatigue
Vitamin deficiency
Failure to thrive
Lactose intolerance
What diseases can coeliac disease get confused with?
- IBS - irritable bowel syndrome
- Wheat allergy
When is someone likely to get coeliac disease?
Onset infant onwards
Describe the structure and function of the ileum and jujenum
Specialised for absorption
Intraperitoneal
Suspended in loops from posterior abdominal wall
How is the surface area of the small intestine increased?
- Villi
- Circular folds (slow down chyme movement)
Describe the anatomy of a villus
- Absorptive cells
- Goblet cell
- Lacteal / lymphatic vessel
- Blood capillaries
- Microvilli
- Duodenal glands
- Enteroendocrine cells
- Intestinal crypt
State the function of goblet cells in villi
Produce mucus
State the function of absorptive cells
Enterocytes
Have microvilli
Where are goblet cells more commonly found?
More numerous in distill end of small intestine
Describe the structure and function of intestinal crypts
Tubular glands
The epithelial cells of intestinal crypts secrete intestinal juice
What stimulates the epithelial cells of the intestinal crypts to secrete intestinal juice?
Acidic chyme
Where are intestinal crypts more commonly found in small intestine?
Proximal end of small intestine (jejunum)
Describe intestinal juice and its function
pH 7.4 - 7.8
1-2 litres secreted daily
Contains molecular digested food products for absorption
Does not contain enzymes
What is the role of enteroendocrine cells?
Secrete enterogastrone hormones including
1. CCK (cholecystokinin) (release stimulated by fats + proteins)
2. Secretin - inhibit gastric acid, stimulates release of bicarbonates
Release T cells (intraepithelial lymphocytes), which releaee cytokines when exposed to antigens
Describe the location and function of paneth cells
Found deep in intestinal crypt
Secrete antimicrobial peptides:
-lysozymes
-defensins
Kill harmful bacteria, allow friendly bacteria to colonise
Describe small intestine cell renewal
Stem cell daughter cells differentiate into:
-absorptive cells
-enteroendocrine cells
-goblet cells
-paneth cells
Old cells removed by apoptosis
Aftet apoptosis, squammting cells shedd the epithelial layer of villi
Villi epithium replaced every 2-4 days
Describe the location of stem cells in the small intestine
Deep at the base of intestinal crypt
Desribe the location and function of the duodenal glands
Found in submucosas of duoednum
Produce alkaline mucos (contains bicarbonate)
to neutralise stomach acid
State the cause of a duodenal ulcer
Inadequate mucus production from duodenal glands
What is the alternative name for the duodenal gland?
Brunner’s gland
State 3 functions of the large intestine
- Reabsorption of water from indigested food
- Absorption of metabolites from bacteria
- Removal of faeces
Describe the positioning of the large intestine
Wraps around small intestine as three sides of a square
Extends from ileocaecal valve to anus
Describe the anatomy of the large intestine
- Transverse Colon
- Ascending colon
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal
- Vermiform appendix
- Cecum
Which arteries supply the large intestine with blood?
Superior mesenteric artery
Inferior mesenteric artery
Which veins drain the large intestine?
Inferioir mesenteric vein - splenic vein - superior mesenteric vein - hepatic portal system
Name the branches of superior mesenteric artery
RIIM
Right colic artery
Intestinal artery
Ileocolic artery
Middle colic artery
Name the branches of the inferior mesenteric artery
RS
Left colic artery
Superior rectal artery
Sigmoidal arteries
What is the function of the rectum?
Temporary storage of faeces
Describe why a patient may suffer from constipation
Defecation does not happen / delayed
Faeces returned to colon
More water absorption occurs
State the function of the rectal valve
Prevent faeces moving with flatus
Why may a patient suffer from haemarrhoids
Haemarrhoid veins inflammed
State the function of anul sinuses
Release mucus when compressed
Describe the anatomy of the rectum and anal canal
Rectal valve
Haemarrhoidal veins
Pectinate line
Anal sinuses
Which nerve fibres surround the pectinate line
Visceral sensory fibres - ANS
Somatic sensory fibres
Describe the mucosa of large intestine
Thick mucosa, lots of intestinal crypts, goblet cells
Colon + Rectum made of simple columnar epithelium
Anal canal - 3 types of epithelium:
Simple columnar epithelium
Stratified squammous epithelium
Stratified squamomous keratanised epithelium
No enzymatic secreting cells, no villi, no circular folds
What are “flora” of the large intestine
Symbiotic Bacteria
Describe symbiotic functions of bacteria in large intestine
Synthesis of vitmains B and K
Metabolises certain secretions - mucin
Ferments carbs (cellulose) producing flatus
List the contents of faeces
- Undigestable food
- Water
- Mucus
- Bacteria
Why is faeces brown?
Contains stercobilin - bile pigement
Produced as a product of haemoglobin breakdown
Without, faeces would be pale white
State the 2 types of motilities which occur in the large intestines
Mode of contractions
- Mass movement / contractions
- Pocket / haustral contractions
Describe mass movement in the large intestine
Slow, long distace
Involves large regions of the colon
Peristalsis
Dietry fibre aids this type of motility
Describe haustall contraction in the large intestine
“pocket movement”
Involves only one haustum
Slow, short distance
Segmentation, mixing of food, aids water reabsorption
Propelling food from one haustum to the next
Exactly where in the large intestine does haustal contraction take place
Ascending, transverse colon
When does mass movement / contraction take place in large intestine
After eating meal - this leads to gastroileal reflex which causes the motility
When does haustral contraction take place in large intestine
as a reaction to distension
