MI 262: Unit 5 (Abdomen)

Lumbar Spine

Forms posterior border of abdominal cavity; five vertebrae, largest vertebrae in size, do not contain transverse foramina and smallest vertebral foramina of all the spine

Diaphragm

Location: Originates from sternal process, costal cartilages, bone of ribs 7-12, upper lumbar vertebrae

Function: Forms a septum between the thoracic and abdominal cavities

Crura (Crus)

Muscular parts of the diaphragm that originate from the lumbar vertebrae and travel to central tendon on right and left sides of the vertebrae

Peritoneum 

Smooth, serous membrane divided into parietal and visceral peritoneums; secretes lubricating fluid that reduces friction between organs and supports organs holding them in place

Parietal Peritoneum

Lines abdominal cavity

Visceral Peritoneum

Lines the outside of the organs

Peritoneal Cavity 

Space between visceral and parietal peritoneum 

Mesentery

Double folded layer of peritoneum in posterior abdomen containing arteries, veins and nerves for intestines; attaches the intestines to the posterior abdominal wall

What is the primary site for fat storage in the body?

Mesentery

Retroperitoneal Space 

Space behind the peritoneal cavity adjacent to the posterior abdominal wall containing the kindeys, pancreas, distal duodenum, ascending colon and descending colon 

Stomach

Upper left side of the abdominal cavity; collapsible reservoir for food with an inner lining (rugae)

Parts of the Stomach

• Fundus

• Body

• Pylorus

Small Intestine 

Extends from the termination of the stomach to the large intestine (5-8 m in length); site of major part of digestion 

What are the parts of the small intestine?

• Duodenum (10 inches)

• Jejunum (9 feet)

• Ileum (11 feet)

Duodenum

First segment of the small intestine extending from pylorus to jejunum; “C” shaped around the head of the pancreas

What is the only part of the small intestine that lies within the peritoneum? 

Duodenum 

Jejunum

Second segment of small intestine extending from duodenum to ileum; usually lies in the umbilical region

Ileum

Longest segment of the small intestine; lies in the lower abdomen and pelvis terminating at the lower right quadrant of the abdomen (ileocecal valve)

Large Intestine 

Extends from the terminal ileum to the anus; 1.5 m in length (5-6 feet) 

Cecum

Right lower side of the abdomen posterior to the peritoneum; first segment of the large intestine

Appendix

Smaller opening at the end of the cecum

Ascending Colon 

Continuous with the cecum along the right lateral abdomen located retroperitoneal; ends at the right hepatic flexure, upper part lies anterior to the right kidney 

Hepatic Flexure

Right upper side of the abdomen next to the liver; connects the ascending and transverse segments of the colon

Transverse Colon

Passes across upper abdomen in the middle region usually lying adjacent to the abdominal wall; leads from hepatic flexure to the splenic flexure

Splenic Flexure 

Bends downwards where transverse colon ends; connects transverse and descending colon 

What flexure in the colon sits higher?

Splenic

Descending Colon

Goes from the splenic flexure to pelvic inlet; joins the sigmoid colon and is fixed in position

Liver

Largest gland of the body lying in the upper right abdominal cavity

Lobes of the Liver 

• Right 

• Left 

• Quadrate 

• Caudate

Porta Hepatis

Transverse fissure, slit on the inferior surface of the right liver lobe; the place where portal vein, hepatic artery, lymphatics and nerves enter the liver

What is the “hilum” of the liver?

Porta hepatis

Left Liver Lobe 

Separated from right lobe by the ligamentum teres, lies anterior to the body of the stomach 

Ligamentum Teres

Connects the liver to the umbilicus

Right Liver Lobe

Largest lobe, sits lateral to the gallbladder

Falciform Ligament 

Attachment of liver to anterior wall of abdomen 

Caudate Liver Lobe

Small, posterior lobe; extends IVC to porta hepatis

Quadrate Liver Lobe

Small, anterior lobe between gallbaldder and ligamentum teres

Hepatic Ducts 

Exit the liver at the porta hepatis; joins to form the common hepatic duct 

Gallbladder

Beneath the liver; reservoir for bile to be produced by the liver

Cystic Duct

Carries bile from the gallbladder to the common hepatic duct

Common Bile Duct 

Posterior to the superior duodenum and beside the head of the pancreas; formed by the cystic duct and the common hepatic duct to transport bile from the gallbladder and liver to the duodenum

Spleen 

Soft, lymphatic organ located in the upper left side of the abdomen; acts primarily as a filter for blod and plays a role with the immune system and red blood cells 

Pancreas

Posterior to the stomach and lies transversely; collection of glandular tissue

Endocrine Function of Pancreas

Insulin/Glucagon

Exocrine Function of Pancreas 

Digestive enzymes 

Pancreas Head

Lies with the curvature of the duodenum

Pancreas Body

Posterior to stomach; anterior to left kidney

Pancreas Tail 

Extending toward the surface of the spleen 

Pancreatic Duct

Runs along inside of the pancreas; joins with the common bile duct and enters the duodenum at sphincter of Odi

Kidneys

Bean shaped organs centered around L1; fluid and waste products are filtered from the blood to form urine; urine collects in the renal pelvis and drains into the ureters, many anomalies may occur in shape and location, retroperitoneal

Ureters 

Retroperitoneal; originate from the renal pelvis of the kindey extending down along the psoas muscles; drain urine downward into bladder, one ureter for each kidney

Adrenal Glands (Suprarenal Glands) 

On the top pole of the kidney; triangular shaped, soft, glandular organ

Endocrine Glands

Produce epinephrine and norepinephrine

Abdominal Aorta

Continuation of thoracic aorta; travels from diaphragm to pelvis (retroperitoneal) on the left side of vertebral bodies; includes many different branches to supply blood to various areas within the body, terminates at left and right common iliac arteries (L4)

Superior Mesenteric Artery

Originates from abdominal aorta extending down; supplies blood to the small intestine and first half of the large intestine (ascending, right half of transverse)

Inferior Mesenteric Artery

Originates from aorta in mid-lumbar region; supplies blood to the left half of large intestine and some of rectum

Renal Arteries

Just below SMA; supply blood to the kidneys; right renal artery is longer, travels behind IVC to the right kidney

Common Iliac Arteries 

Bilateral arteries arising from the abdominal aorta (L4); bifurcate into left and right internal and external arteries 

Inferior Vena Cava

Found on the right side of the heart, anterior to esophagus and descending aorta formed by the union of right and left common iliac veins (L5); drains most of lower half of the body into the right atrium

Renal Veins

Left vein is longer, crosses in front of aorta to IVC; drains blood from the kidneys emptying into the IVC

Common Iliac Veins (Right and Left) 

Arise at the juncture of left and right internal and external iliac veins anterior to L5-S1 joint space exending a short distance to join around L4, more posterior and inferior than iliac arteries; drrains venous blood from lower limbs and pelvis into the IVC 

Psoas Muscles

Originate from the transverse processes of L1-L5 inserting on the lesser trochanter of the femur on either sides, forms part of the posterior abdominal wall; round structure on either side of vertebral column useful in finding the ureters

Rectus Abdominus

Muscles lining either side of the anterior abdominal wall; originates at pubic symphysis and iliac crest, inserts on cartilage of 5th-7th ribs and xiphoid process