GI System - 1 Flashcards
List 10 components of the alimentary canal.
Mouth Tongue Pharynx Oesophagus Stomach Small intestine Colon of large intestine Appendix Rectum Anus
How many layers does the gut wall have?
Four
What are the layers of the gut wall?
Mucosa (innermost)
Sub mucosa
Muscularis Externae
Serosae (outermost)
What are Peyer’s patches and where are they typically aggregated in the layers of the GI tract?
Group of lymph nodes forming a single layer in the lamina propria (part of mucosal membrane) of the distal ileum.
Sometimes present in jejunum
What structures are present in the gut wall submucosa?
Glands
Nerves
Blood vessels
All within this layer of connective tissue
What is the muscularis externae comprised of?
2 layers of smooth muscle
Outer longitudinal layer of smooth muscle
Inner circular layer of smooth muscle
How do luminal contents move along the gut?
Peristaltic wave action of the muscularis externae
Name 8 major functions of the GI tract.
Providing port of entry
Mechanical disruption
Temporary store of food
Chemical digestion
Kill pathogens in food
Move food along GI tract
Absorb nutrients from resultant solution
Remove residual waste
During digestion we want to convert our food into a solution that is…. (Name 3 characteristics)…
Relatively sterile
Neutral pH
Isotonic
List the accessory organs of the GI Tract
Liver
Gallbladder
Pancreas
Salivary Glands
What nay s arp resent I. Saliva
Amylase and lipase
How does saliva protect teeth?
Bacteria static (IgA)
High calcium
What is th name of the main mastication muscles?
Master muscles
Voluntary control of digestion is found where in the GI tract?
Upper end of oesophagus
How long does peristaltic transport take to move bonus through the oesophagus?
Approximately 8-9s
What is the innermost and outmost innervation of the oesophagus?
Submucosal plexus
Myenteric plexus
How is th stomach adapted to storage, initial disruption and disinfection?
- Food store
- Receptive relaxation so pressure does not rise
- Rhythmic contractions with rugae
- Secretes HCl and proteolytic enzymes e.g. Pepsinogen
- Secrete mucus to protect epithelium
- Produces hypertonic chyme by action of acid, enzymes and agitation
- Slowly delivers incompletely digested chyme to the duodenum
The Liver and Pancreas connects with which portion of the duodenum?
2nd Part
How is chyme’s hypertonic state dealt with in the duodenum?
Water is drawn in from the ECF to render the chyme isotonic
What structure releases bile?
What does bile consist of?
Liver
Water, alkali, bile salts
How is the gut adapted or absorption?
Gut is folded
Villi
Microvilli
All 3 act to increase surface area
What is the length and width of the small intestine?
22 feet (7 meters)
1 inch, 2.5 cm long
What is the surface area of the small intestine?
25 meters squared.
There is much folding especially in the proximal region of the duodenum
What are Plicae Circulares?
Circular folds of mucosa and submucosa which project into the gut lumen
Where does most of the active absorption take place in the small intestine?
At proximal duodenum
From beginning to end, what are the features of the large intestine?
Caecum Ascending colon Right hepatic flexure Transverse colon Left splenic flexure Descending colon Sigmoid colon Rectum
What epithelium is found in the colon of the large intestine?
Simple columnar
What do crypts of Lieberkuhn do?
Produces much mucus and provides cells to the surface
What is a function of the large intestine?
Continue water resorption
Contents await expulsion in the colon, NOT the rectum
How is defecation stimulated?
Contents await expulsion in colon but at times are rapidly expelled into rectum, stretching the rectum and giving the urge to defecate
Describe the balance sheet of the gut (produced)
1 kg ingested
- 5L of saliva in mouth
- 5L of gastric secretions
9L of water / alkali from Small Intestine
Total 14L
What is the balance sheet of the gut (dealt with)
Small intestine absorbs 12.5L
Large intestine absorbs 1.35L
0.15L excreted in faeces
What mechanisms ensure motility and secretion control of fluid balance in the gut?
Neural
Paracrine
Endocrine
Where is the GI system und somatic innervation?
At site of immediate ingestion and excretion:
Mouth and first third of oesophagus
Last sphincter of anus
What plexus eyes are formed in the GI tract and where are they located?
My enteric plexus - formed between the muscle layers of the gut wall
Submucosal plexus - beneath the mucosa
From serosa even to lumen, name the layers of the gut wall.
Serosa: epithelium & areolar connective tissue
Circular muscle Longitudinal muscle Submucosa Muscularis mucosae Lamina Propria Epithelium of Mucosa Lumen
What is another name for the Submucosal Plexus?
Plexus of Meissner
How is histamine involved in paracrine control of gut function?
Histamine acts locally to control the production of gastric acid.
List the 6 accessory digestive organs
Teeth Tongue Salivary glands Liver Gallbladder Pancreas
Name the 6 basic processes of the digestive system.
- Ingestion
- Secretion
- Mixing and Propulsion (Motility)
- Digestion
- Absorption
- Defecation
The layers of the GI tract are what?
4 - Mucosa
3 - Submucosa
2 - Muscularis
1 - Serosa
What is the rate of renewal of GI tract epithelial cells?
5 to 7 days. Rapid
Where can simple columnar be found in the GI tract?
What is its function?
Found in stomach and intestines.
Function: Absorption and Secretion
What is the function of tight junctions between neighbouring simple columnar cells?
Avoid or restrict leakage between the cells.
What are the endocrine cells of the GIT also called?
Enteroendocrine cells
What structure anatomically divides the anterior portion of the liver?
Falciform ligament
What is areolar connective tissue and what is it comprised of?
A mesh form of loose connective tissue.
Comprised of:
Collagen, Elastic and Reticulin Fibres
What type of tissue is the Lamina Propria of the GIT? What structures are found here?
Areolar connective tissue
Can find Blood Vessels, Lymphatic Vessels and cells of Mucosa Associated Lymphatic Tissue (MALT)
How is the stomach and small intestine’s mucous membrane surface area increased?
Thin layer of muscularis mucosae throws the mucous membrane into many small folds, increasing the surface area for digestion and absorption
What is the submucosa comprised of?
Areolar connective tissue
Blood & Lymphatic Vessels
Submucosal Plexus
Glands
Lymphatic tissue
Where is the myenteric plexus found?
Between the inner circular and outer longitudinal layers of smooth muscle.
Between the layers of the muscularis essentially
Where is skeletal muscle under voluntary control found in the GI tract?
Mouth
Pharynx
Superior and middle region of oesophagus
External anal sphincter
What is another name for the serosa of the GI tract portions suspended in the abdominopelvic cavity?
Visceral peritoneum
What is the serosa of the GIT comprised of?
Areolar connective tissue
Simple squamous epithelium (mesothelium).
What portion of the GI tract lacks a serosa?
What is in place of the serosa?
Oesophagus.
Single layer of areolar connective tissue called the adventitia forms that superficial layer of the oesophagus
