Lecture 18: Abdominal viscera Flashcards
What does the GI tract consist of?
Esophagus
Stomach
Small intestine
Large intestine (colon)
What is the esophagus? Role?
Long,muscular tube that carries food from the oral cavity to the stomach (peristalsis)
What does the esophagus extend through?
Extends through the posterior mediastinum, and passes through the diaphragm (at T10) to reach the stomach
What region of the abdomen is the stomach located in?
Left hypochondriac and epigastric regions
Underneath diaphragm and partially shielded by the ribs
Parts of the stomach
Cardia – area surrounding the opening of
the esophagus. Contains esophageal sphincter, which prevents acid from coming back up from stomach
Fundus – located beneath the left dome of
diaphragm (above the cardia). Where gas and other substances accumulate
Cardiac notch - angle between the
esophagus and fundus
Body – located between fundus and pyloric
antrum
Pyloric Antrum – funnel shaped region of
stomach between the body and pyloric canal
Pyloric canal – narrower than the antrum,
contains the pyloric sphincter (pylorus).
See figure
Internal surface of the stomach
The internal surface of the stomach is highly ridged. These mucosal folds are called rugae
Increase surface area of stomach, allowing absorption of nutrients and expansion of stomach to accommodate food
What is the role of the pyloric sphincter?
thick band of muscle
controls the passage of stomach contents into the duodenum
See figure
Parts of the small intestine
Duodenum
Jejunum
Ileum
How long is the small intestine in an adult?
Approximately 7 metres
Role of small intestine
Main site of nutrient absorption
Length of duodenum
25 cm
Shortest part of small intestine
Four parts of duodenum
1- Superior (1st):
lies anterolateral to the body of the L1 vertebra
2- Descending (2nd): descends along the right side of the L1- L3 vertebrae. Location of major duodenal papilla, entrance of bile duct and pancreatic duct
3-Horizontal (3rd): crosses the L3 vertebrae.
4-Ascending (4th): begins at the left of the L3 vertebrae, ascending to the superior border of the L2 vertebrae.
See figure
Location of the jejunum and the ileum
Suspended from the posterior abdominal wall by the mesentery, very mobile
How to distinguish between the jejunum and the ileum
No distinct border between the jejunum and ileum
Generally, the jejunum is found in the left upper quadrant, ileum in the right lower quadrant
See figure and table
Which parts of the duodenum are intraperitoneal and retroperitoneal
The superior part has an intraperitoneal part and a retroperitoneal part
Where does the large intestine extend from?
From the ileocecal junction to the anus (1.5 m long)
Parts of large intestine
Cecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
Anal canal
See figure
Role of large intestine
Reabsorbs water and electrolytes (waste management)
Distinguishing features of large intestine
Teniae coli (orange)
Haustra
Epiploic appendages (yellow)
What are the tenia coli?
3 longitudinal bands of smooth muscle
What are the haustra? How are they formed? Role?
Sacculations found along the length of the large intestine
Formed by the action of the teniae coli (like the elastic band on sweatpants!)
Help with reabsorption of water
What are the epiploic appendages?
Small peritoneal pouches filled with fat
Not sure what they do, everyone has them
What is the cecum? location?
First part of the large intestine
Continuous with the ascending
colon
Point where the ileum meets the
large intestine
What is the vermiform appendix? Location? Importance?
Blind-ending tube, worm-shaped!
Usually found posterior to the cecum (retrocecal)
Site of appendicitis!
See figure
What is the largest solid organ in the body?
The liver
Has the most vasculature
Functions of the liver
Major metabolic organ – fats, proteins and carbohydrates
Glycogen synthesis and storage
Production of bile (fat digestion)
Detoxification of blood (excretion of bilirubin, metabolism of alcohol and other drugs)
What is billirubin? Colour?
Product of heme metabolism
Excreted in the bile
Yellow
Jaundice = build up of bilirubin, something wrong with liver
What are the four lobes of the liver?
Right lobe
Left lobe
Quadrate lobe (next to gallbladder)
Caudate lobe (next to inferior vena cava)
Ligaments of the liver
Coronary ligament (attaches to diaphragm)
Falciform ligament (attaches to anterior abdominal wall)
What is the importance of the porta hepatis?
Door to the liver
Location of the portal vein, hepatic artery, and common hepatic duct
Trajectory of bile
Bile is produced in the liver and is secreted into the common hepatic duct
Gallbladder stores and concentrates bile
When it contracts, it expels bile through the cystic duct (bile can flow both ways), and into the common bile duct (cystic and hepatic duct join to form common bile duct)
Enters the duodenum where it helps emulsify fats
See figure
Shape and parts of pancreas
Flat, leaf-shaped, gland
Includes head, body,
and tail
Anatomical location of pancreas
Retroperitoneal
Tucked into a curve of the duodenum
See figure
Functions of pancreas
Endocrine: produces
hormones that regulate blood sugar – insulin, glucagon
Exocrine: produces digestive enzymes – trypsin, chymotrypsin (aka. pancreatic juice)
Pancreatic and bile duct meeting point
Pancreatic duct and the common bile duct meet and open into the duodenum at the duodenal papilla
See figure
Where is the spleen located?
Far upper left quadrant of the abdomen
Right against diaphragm
Shielded by the ribs
See figure
Functions of the spleen
Lymphatic organ -
filters blood to remove old erythrocytes
Immune organ – contains B and T lymphocytes
Stores about 230 ml of blood
What is the blood supply of the abdominal viscera?
3 major unpaired branches of the abdominal aorta:
Celiac trunk
Superior mesenteric artery
Inferior mesenteric artery
See figure
What are the organs supplied by the celiac trunk?
Stomach, spleen, liver, pancreas, part of duodenum
What are the organs supplied by the superior mesenteric artery?
remainder of duodenum, jejunum, ileum, cecum and appendix, ascending colon, part of transverse colon
What are the organs supplied by the inferior mesenteric artery?
remainder of transverse colon, descending colon, sigmoid colon, rectum
What are the branches of the celiac trunk?
See figure
3 main branches: left gastric artery, splenic artery, common hepatic artery
What are the branches of the superior mesenteric artery (small intestine)?
Inferior pancreaticoduodenal artery: Supplies pancreas and duodenum (distal to the duodenal papilla)
Jejunal and ileal arteries: form arcades (loops)within the mesentery
Vasa recta (straight) enter the intestinal wall
See figure
What are the branches of the superior mesenteric artery (large intestine)?
Ileocolic artery: distal ileum, cecum, appendix, ascending colon
Right colic artery: ascending colon
Middle colic artery: transverse colon (2/3 of it)
See figure
What are the branches of the inferior mesenteric artery?
Left colic artery: remaining 1/3 of transverse colon, descending colon
Sigmoid arteries: descending colon, sigmoid colon
Superior rectal artery: rectum
See figure
Systemic vs portal circulation
See table
Portal venous drainage
The superior mesenteric vein and splenic vein join to form the hepatic portal vein (large, 8 cm long)
Inferior mesenteric vein drains into splenic vein
Hepatic portal vein drains blood from the unpaired abdominal organs (stomach, spleen, pancreas, gallbladder, small intestine, large intestine) and carries it to the liver for processing of nutrients and removal of toxins
See figure
Why do we have the portal system?
Nutrients are absorbed quicker by the liver, so the portal system allows them to be distributed quicker than they would if there was only systemic
Ingested poisons and toxins would get to the heart and the brain if it weren’t for the portal system
