Abdominal Wall Muscles and Sheath

Abdominal Wall Muscles and Sheath

• The external oblique muscle is the most superficial of the abdominal oblique muscles
• The anterior rectus sheath is a connective tissue structure and is formed by the aponeuroses of the external and internal oblique muscles, enclosing the front of the rectus abdominis muscles
• The internal oblique muscle is the deepest of the abdominal oblique muscles
• The rectus sheath is a connective tissue structure that encloses the right and left sides of the rectus abdominis muscle, and is formed by the aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles
• Rectus abdominis muscle is found beneath the rectus sheath
• The belly button is also known as the umbilicus
• The linea alba is a connective tissue that runs from the pubis to the xiphoid process
• The transversus abdominis muscle is the deepest of the external and internal oblique muscles
• This muscle runs transversely/horizontally, and can be considered a "waist trainer"
• The posterior rectus sheath is a connective tissue structure that forms the posterior covering of the rectus abdominis muscle
• It is made up of the aponeuroses of the internal oblique and transversus abdominis muscles
• Order of abdominal cut: External Oblique M. → Internal Oblique M. → Transversus Abdominis M
• Order of abdominal cut: Anterior Rectus Sheath → Rectus Sheath → Posterior Rectus Sheath

Inguinal Canal

• The inguinal ligament forms the floor of the inguinal canal
• The round ligament runs through the inguinal canal in females
• The spermatic cord runs through the inguinal canal in males

Conditions Within the Inguinal Canal:

• If an inguinal hernia is indirect, it will travel through the wall lateral to the epigastric vessels
• It will follow the path of the inguinal canal
• If an inguinal hernia is direct, it will travel through the wall medially to the epigastric vessels
• It will protrude through the abdominal wall directly, and the inguinal canal

Basic Functions of the Organs

• Lungs serve to oxygenate blood
• Heart serves to pump blood
• Esophagus helps to push food down
• Stomach chemically digests food
• Pancreas produces insulin to regulates blood sugar
• Spleen removes old or damaged red blood cells from circulation
• Liver produces bile
• Gallbladder stores bile
• Small intestine absorbs the most nutrients in the digestive system
• Large intestine produces B and K vitamins through bacterial cells and storage of feces
• Rectum holds fecal matter
• Suprarenal/Adrenal glands produces adrenaline
• Kidney produces urine
• Ureters are tubes that help carry urine
• Bladder stores urine

Esophagus & Stomach

• The esophagus goes through the esophageal hiatus in the diaphragm
• The lower esophageal sphincter controls the passage of food from the esophagus into the stomach, preventing acid reflux
• The region of the stomach where the esophagus connects and food enters is the cardia
• The fundus is the part of the stomach that often stores undigested food and gas
• The pyloric sphincter is a muscular valve controls the passage of digested food from the stomach into the small intestine
• Gastric rugae are the folds in the stomach lining that allow it to expand when full
• The lesser omentum connects the lesser curvature of the stomach to the liver
• The space behind the lesser omentum and stomach is the omental bursa

Liver & Gallbladder

• The liver has 4 lobes
• The right lobe is larger than the left
• The gallbladder lies between the quadrate and right lobes
• The falciform ligament is on the anterior side of the liver, helping to suspend it and connect it to the front of the abdomen
• The round ligament is on the inferior side of the liver
• The 3 veins that branch off the inferior vena cava and go into the liver are the right hepatic, middle hepatic, and left hepatic veins
• These all come off of common
• The gallbladder is a small, pear-shaped organ under the liver responsible for storing and concentrating bile
• The cystic duct carries bile from the gallbladder to the common bile duct
• The right and left hepatic ducts drain into the common hepatic duct

Flow of Bile

• If bile is needed immediately for digestion: Liver → Right and Left Hepatic Duct → Common Hepatic → Common Bile Duct → Duodenum
• If bile is not needed immediately for digestion: Liver → Right and Left Hepatic Duct → Common Hepatic Duct → Cystic Duct → Gallbladder → Cystic Duct → Common Bile Duct → Duodenum

Spleen

• The spleen is between the 9th, 10th, and 11th ribs
• The spleen is part of the immune system
• The spleen fights germs in the blood
• The splenic artery branches off the celiac trunk
• The splenic vein drains into the portal vein

Pancreas & Duodenum

• The pancreas is behind the stomach and plays a critical role in digestion by releasing enzymes
• The main pancreatic duct carries digestive enzymes to the small intestine
• The pancreas has exocrine and endocrine glands
• The main pancreatic duct joins with the common bile duct before emptying into the duodenum
• The duodenum is where the small intestine starts
• The duodenum is also known to be "C’ shaped
• When the accessory pancreatic duct empties into the duodenum, it is known as the minor duodenal papilla
• The major duodenal papilla is the location where the main pancreatic duct and the common bile duct join together and empty into the duodenum
• The duodenum is responsible for receiving bile from the liver and pancreas to aid in digestion
• The minor duodenal papilla is superior to the major duodenal papilla

Kidney

• There are 2 kidneys
• The suprarenal gland is superior to the kidney
• The right kidney sits lower since the liver is on top
• The left renal vein is longer
• There are 3 layers to the kidney
• The renal pyramid is found in the renal medulla and plays a role in urine formation
• The renal pelvis collects urine and directs it into the ureter
• The ureter is a structure helps to carries urine to the bladder

Layers of the Kidney

• Renal capsule: the outermost layer and is composed of a thin fibrous membrane
• Renal cortex: the middle layer and is located under the capsule, and contains nephrons that are responsible for filtering blood and producing urine
• Renal medulla: is the inner layer that contains renal pyramids

Small and Large Intestine

• The greater omentum is the large, fatty apron-like structure that hangs down from the stomach and covers the intestines
• The order in the small intestine is: duodenum → jejunum → ileum
• The mesentery is a structure that holds the small intestine in place and contains blood vessels and nerves
• The jejunum is more superior
• The jejunum is where there is the most absorption
• The ileum is where there is the least absorption
• The jejunum’s circular folds are thicker and wider
• The ileum’s circular folds are small and thin
• The small intestine is medial to the large intestine
• The mesocolon anchors the colon to the abdominal wall and provides support and stability in the large intestine
• The order in the large intestine is: cecum → ascending → transverse → descending → sigmoid → rectum
• The ileocecal junction is where the ileum and cecum connects
• The appendix hangs off the cecum and it serves as reservoir for good bacteria and contains immune cells
• The haustra helps increase surface area in the large intestine

Colon

• The Tenia coli is a longitudinal smooth muscle band that helps with movement in the large intestine
• The flexure between the transverse colon and the descending colon is called the left colic flexure
• The large intestine is lateral to the small intestine

Nerves

• C3-C5 are the roots of the phrenic nerve
• T1-T11 are the roots of the intercostal nerves
• S2-S4 are the roots of the pudendal nerves
• T1-L2 are the roots of the sympathetic trunk
• The vagus nerve innervates the left colic flexure
• S2-S4 are the roots of the pelvic splanchnic nerves

Sacral Autonomic Nerves

• Parasympathetic nerves stimulate urination, defecation, and erection
• Sympathetic nerves inhibit urination, defecation, and control ejaculation

Pudendal Nerve Distribution

• Sensory or motor innervation: Penis/Clitoris, Anus and lower anal canal, External Anal Sphincter, Perineum, labia majora/scrotum, and Perineal Muscle
• The visceral is superior to the pectinate line
• The inferior mesenteric artery supplies pectinate line
• The rectal artery supplies the inferno part of pectinate line
• The Internal iliac artery supplies the inferio part of pectinate line
• The Inferior vena cava drain of the interior part of pectinate line