1 A: GI System Flashcards
What is the GI Tract?
An epithelial lined muscular tube about 30 ft i length
What are parts of the GI ?
- Mouth
- pharynx
- esophagus
- stomach
- small intestine (duodenum, jejunum, ileum)
- large intestine/ colon (cecum, ascending, transverse, descending & sigmoid colons)
- rectum
- anus
Why is the length of the GI half the length?
Due to muscle tone
What are the ACCESSORY DIGESTIVE ORGANS ?
Salivary glands, pancreas & biliary system (liver & gall bladder)
What is the basic functions of the GI tract?
1) Separate ingested food into essential nutrients & unnecssary wastes
2) Absorb the former while getting rid of the latter
To carry out these tasks what mechanisms has the GI tract developed?
1) Motility
2) Secretion
3) Digestion
4) Absorption
What is tone?
Smooth muscle in the walls of the GI tract maintinas a constant low level of contractions known as tone
(e.g “bowl sounds”)
Why is tone important?
Maintains a steady pressure on the contents of the GI tract as well as in prevents its walls from remaining permanently stretched following distention.
What are the 3 basic types of motility?
1) Propulsive movements or PERISTALSIS
2) Mixing movements or SEGMENTATION
3) TONIC CONTRACTIONS of sphincters or valves
What is the function of Peristalsis ?
Propulsive causes transport non-propulsive causes mixing
What is the site of Peristalsis ?
1) Esophagus 2) Stomach 3) Small intestine
What is the function of Rhythmic segmentation?
Mixing
What is the site of Rhythmic segmentation?
1) Small intestine 2) Large intestine
What is the function of Tonic contraction?
1) Blocking passage 2) Separation
What is the site of Tonic contraction ?
1) Gastrointestinal sphincters
How does Peristalsis work?
Propels contents forward throughout the GI tract at varying speeds.
***Completely dependent on involuntary contractions of smooth muscle
What are the different kinds of segmentation?
1) Regularly spaced
2) Isolated
3) Irregularly spaced
4) Weak regularly spaced
What does segmentation do ?
1) Promotes mechanical digestion of food
2) Facilitates absorption by exposing all portions of the intestinal contents to the absorbing surfaces of the GI tract
*****Dependent on involuntary contractions of smooth muscle
What do Sphincters do?
Tonic contractions of sphincters, w/ intermittent relaxation, also serve to regulate the movement of luminal contents
What is the relaxation of sphinters mediated by?
reflexes
*****completely dependent on INVOLUNTARY CONTRACTIONS OF SMOOTH MUSCLE (autonomic)
What are the GI sphincters WITHIN the GI TRACT?
1) Upper Esophageal Sphincter (UES)
2) Lower Esophageal Sphincter (LES)
3) Pyloric Sphincter
4) Ileocecal Sphincter
5) Internal Anal Sphincter
6) External Anal Sphincter
What are the GI sphincters INTO the GI TRACT?
1) Sphincter of Oddi
What does the Sphincter of Oddi do?
Regulates the movement of contents of the common BILE DUCT into DUODENUM
Do we have voluntary control of GI motility? Explain
Yes;
1) At the mouth thru the early portion of the esophagus (including the UES)
2) At the external anal sphincter
What are the activities involved in these two exceptions of voluntary movement?
Motility involves skeletal muscle rather than smooth muscle activity
What are some examples of voluntary movements done by skeletal muscle ?
1) chewing 2) swallowing 3) defecation
What is the motility accomplished by smooth muscle accomplished by ?
Smooth muscle thru the remainder of the tract which is controlled by involuntary mechanisms.
What does Secretion in the GI tract involve?
Process by which water, electrolytes, and proteins are exported out of cells
How much saliva, gastric juice, bile, pancreatic juice, intestinal secretions, and mucus does the body make a day?
TOTAL = 9 L of fluids
- 5 L saliva
- 5 gastric juice
- 5 L Bile
- 5 L pancreatic juice
- 0 L intestinal secretions
- 0 L mucus
***Variations in both ionic & molecular composition
What is digestion ?
The breakdown process whereby the structurally complex food stuffs of the diet are converted into smaller absorbable units
How does digestion occur ?
Mechanically via the aforementioned motility & chemically via enzymes
What is the underlying mechanism of most chemical digestion ?
Hydrolysis
Where are the enzymes secreted from that go into the GI tract?
1) Stomach
2) pancreas
3) The plasma membrane of enterocytes (brush border enzymes)
4) Epithelial cells that make up the mucosal surface of the GI tract
Where does digestion mainly occur?
Small intestine and Stomach
What does Absorption in the GI tract solve?
1) How to reclaim enormous volume of fluid (9L), entering or secreted into the lumen of the GI tract each day.
* ** 100 ml ends up in still and rest of it recycled
2) Recognizes specific nutrients, vitamins, electrolytes(water) and to absorb them effectively & efficiently (via active and passive transport)
What are the 4 basic quadrants ?
1) Right Upper
2) Left Upper
3) Right Lower
4) Left Lower
What are the GI organs in the Right upper quadrant (RUQ)
1) Liver: right lobe
2) Gallbladder
3) Duodenum: parts 1-3
4) Pancreas: head
5) Right kidney
6) R. colic (hepatic) flexure
7) Ascending colon: superior part
8) Transverse colon: right half
9) Stomach: pylorus
What are the GI organs in the Left upper quadrant (LUQ)
1) Liver: Left lobe
2) Spleen
3) Stomach
4) Jejunum & proximal ileum
5) Pancreas: body & tail
6) L. kidney
7) L. Colic (splenic) flexure
8) Transverse colon: left half
9) Descending colon: superior part
What are the GI organs in the Right lower quadrant (RLQ)
1) Cecum
2) Vermiform appendix
3) Most of ileum
4) Ascending colon: inferior part
What are the GI organs in the Left lower quadrant (LLQ)
1) Sigmoid colon
2) Descending colon: inferior part
What are the 9 Abdominal Pelvic regions?
1) Umbilical
2) R. Lateral (Lumbar)
3) L. Lateral (Lumbar)
4) Epigastric
5) R. Hypochondriac
6) L. Hypochondriac
7) Pubic
8) R. Inguinal (Grion)
9) L. Inguinal (Grion)
What is the largest of the ventral body cavities?
GI organs inside the abdominopelvic cavity
What is the peritoneum?
a slick serous membrane of the abdominopelvic cavity
What does the visceral peritoneum cover?
The external surfaces of digestive organs & is continuous w/ parietal peritoneum
What does the parietal peritoneum line?
The walls of the abdominopelvic cavity
What is between the 2 peritoneums?
The peritoneal cavity. a slit-like space containing peritoneal fluid secreted by the 2 membranes
What does the serous fluid lubricate? and what does it allow?
The mobile digestive organs, allowing them to glide easily across one another as they carry out activities.
What is Peritonitis? When does it occur?
Inflammation of the peritoneum
-Occurs when one suffers a piercing wound of the abdomen, a perforating ulcer, or a ruptured appendix.
What is Ascites ?
The condition characterized by the accumulation of peritoneal fluid (EDEMA in the abdomen)
What does the peritoneum contain?
Large folds that weave between the viscera
Unlike the pericardium and pleurae
What are 2 examples of the peritoneum? Where are they located?
1) The GREATER OMENTUM
- Hangs loosely from the transverse colon & small intestine
2) MESENTERY
-Found in between the small intestine & anchors it to the posterior abdominal wall
(more fat tissue, deep in belly )
