Abdominal Anatomy and Viscera Overview

What are the 9 regions of the abdomen?

Right hypochondrium, Epigastric, Left hypochondrium, Right lumbar (lateral), Umbilical, Left lumbar (lateral), Right inguinal/iliac, Pubic (hypogastric), Left inguinal/iliac.

What planes delineate the 9 abdominal regions?

4 planes: 2 sagittal (midclavicular and semilunar lines) and 2 transverse (subcostal and transtubercular planes).

What is the significance of the transpyloric plane?

It is a horizontal line through the L1 vertebra, key for locating the 8th costal cartilage.

What are the key organs present in the Right Upper Quadrant?

Liver (right lobe), Gallbladder, Stomach (pylorus), Duodenum (parts 1-3), Pancreas (head), Right suprarenal gland, Right Kidney, Right colic (hepatic) flexure, Ascending colon (superior part), Transverse colon (right half).

What are the key organs present in the Left Upper Quadrant?

Liver (left lobe), Spleen, Stomach, Jejunum and proximal ileum, Pancreas (body and tail), Left suprarenal gland, Left kidney, Left colic (splenic) flexure, Descending colon (superior part), Transverse colon (left half).

What are the key organs present in the Right Lower Quadrant?

Cecum, Appendix, Ileum (most of), Ascending colon (inferior part), Right ovary, Right uterine tube, Right ureter (abdominal part), Right spermatic cord (abdominal part), Uterus (if enlarged), Urinary bladder (if full).

What are the key organs present in the Left Lower Quadrant?

Sigmoid colon, Descending colon (inferior part), Left ovary, Left uterine tube, Left ureter (abdominal part), Left spermatic cord (abdominal part), Uterus (if enlarged), Urinary bladder (if full).

What are the borders of the anterolateral abdominal wall?

Superior: Cartilages of 7th to 10th ribs, Xiphoid process of sternum; Inferior: Inguinal ligament, superior margins of the pelvic girdle.

How many layers compose the abdominal wall, and what are they?

8 layers: Skin, Superficial fascia (Camper and Scarpa fascia), Investing superficial fascia (External oblique), Investing intermediate fascia (Internal oblique), Investing deep fascia (Transversus Abdominis), Endoabdominal fascia, Extraperitoneal fat, Peritoneum.

What are the three paired flat muscles of the abdominal wall?

External oblique, Internal oblique, Transversus abdominis.

What are the two paired vertical muscles of the abdominal wall?

Rectus abdominis, Pyramidalis.

What is the clinical significance of the abdominal regions and quadrants?

They help in describing the location of organs, pain, or pathologies.

What is the function of the inguinal canal?

It is a passage for structures such as the spermatic cord in males and the round ligament in females.

What is the role of the peritoneum in the abdominal cavity?

It is a serous membrane that lines the abdominal cavity and covers the abdominal organs.

What is the neurovasculature associated with the abdominal wall?

It includes the lower intercostal nerves, subcostal nerve, iliohypogastric nerve, and ilioinguinal nerve.

What is the lymphatic drainage pattern of the abdominal wall?

Lymphatic drainage primarily follows the venous drainage patterns, with lymph nodes located along major blood vessels.

What is the significance of the rectus sheath?

It provides support and protection to the rectus abdominis muscle and contains the neurovasculature.

What is the function of the abdominal muscles?

They assist in movements such as flexion, rotation, and stabilization of the trunk.

What is the role of the extraperitoneal fat?

It provides cushioning and insulation for the abdominal organs.

What are the potential clinical implications of abdominal wall hernias?

They can lead to pain, obstruction, or strangulation of abdominal contents.

What is the significance of the abdominal fascia layers?

They provide structural support, compartmentalization, and protection for the abdominal organs.

What are the origins of the External Oblique muscle?

External surfaces of 5th-12th ribs.

Where does the External Oblique muscle insert?

Linea alba, Pubic tubercle, Lateral lip of iliac crest.

What is the innervation of the External Oblique muscle?

T7-T11 spinal nerves and Subcostal nerve.

What are the main actions of the External Oblique muscle?

Compress abdominal contents; Both muscles flex trunk; Each bends trunk to the same side; Each rotates trunk to the opposite side.

What is the origin of the Internal Oblique muscle?

Thoracolumbar fascia, Anterior 2/3 of iliac crest, Connective tissue deep to lateral 1/3 of inguinal ligament.

Where does the Internal Oblique muscle insert?

Inferior borders of 10th-12th ribs, Linea alba, Pecten pubis via conjoint tendon.

What is the innervation of the Internal Oblique muscle?

T6-T12 and L1 spinal nerves.

What are the main actions of the Internal Oblique muscle?

Compress abdominal contents; Both muscles flex trunk; Each bends trunk and turns the anterior part of the abdomen to the same side.

What is the origin of the Transversus Abdominis muscle?

Internal surfaces of 7th-12th costal cartilages, Thoracolumbar fascia, Iliac crest, Connective tissue deep to lateral 1/3 of inguinal ligament.

Where does the Transversus Abdominis muscle insert?

Linea alba, aponeurosis of internal oblique, Pubic crest, Pecten pubis via conjoint tendon.

What is the innervation of the Transversus Abdominis muscle?

T6-T12 and L1 spinal nerves.

What is the main action of the Transversus Abdominis muscle?

Compress abdominal contents.

What is the origin of the Rectus Abdominis muscle?

Pubic symphysis and Pubic crest.

Where does the Rectus Abdominis muscle insert?

Xiphoid process and 5th-7th costal cartilages.

What is the innervation of the Rectus Abdominis muscle?

T6-T12 spinal nerves.

What are the main actions of the Rectus Abdominis muscle?

Compress abdominal contents; Flex lumbar vertebrae; Controls tilt of pelvis.

What is the origin of the Pyramidalis muscle?

Front of pubis and Pubic symphysis.

Where does the Pyramidalis muscle insert?

Linea alba.

What is the innervation of the Pyramidalis muscle?

T12 spinal nerve.

What is the main action of the Pyramidalis muscle?

Tenses the linea alba.

What is the Rectus Sheath?

A strong, incomplete fibrous compartment enclosing the rectus abdominis and pyramidalis, containing epigastric arteries/veins, lymphatics, and thoraco-abdominal nerves (T7-T12).

What is the significance of the Arcuate line?

It marks the transition in the posterior rectus sheath composition, located one third distance from the umbilicus to the pubic crest.

What is the function of the Linea Alba?

Interlacing fibers of the anterior and posterior layers of the rectus sheath that separates the bilateral rectus sheaths.

What is the Umbilical Ring?

The area in the middle of the linea alba beneath the umbilicus where all layers of the anterolateral abdominal wall fuse.

What are the main arteries supplying the abdominal wall?

Superior and Inferior Epigastric arteries, Musculophrenic, 10th & 11th posterior intercostal, Subcostal, Deep and Superficial Circumflex Iliac, Superficial Epigastric arteries.

What are the potential sites for hernias in the abdominal wall?

Supravesical fossa, Medial inguinal fossa (inguinal triangle), Lateral inguinal fossa.

What is the Inguinal Region?

Also known as the groin, it extends between the anterior superior iliac spine and pubic tubercle.

What is the Inguinal ligament?

The inferior margin of the external oblique aponeurosis, forming part of the bilaminar flexor retinaculum of the hip joint along with the iliopubic tract.

Describe the Inguinal Canal.

An oblique passage 4cm long directed inferomedially, lying parallel and superior to the medial half of the inguinal ligament.

What is the Deep (internal) inguinal ring?

An oval structure that is larger in males than females, an evagination in the transversalis fascia, located superior to the middle of the inguinal ligament and lateral to the inferior epigastric artery.

What is the Superficial (external) inguinal ring?

A triangular slit in the external oblique aponeurosis, superolateral to the pubic tubercle.

What are the boundaries of the Inguinal Canal?

Posterior wall: Transversalis fascia; Anterior wall: Internal oblique & lateral crus; Roof: Transversalis fascia; Floor: Iliopubic tract.

What contents are found in the Inguinal Canal for both males and females?

Ilioinguinal nerve, sympathetic nerves, and lymphatics.

What additional contents are found in the male Inguinal Canal?

Spermatic cord, including vas deferens, testicular artery, artery to vas deferens, cremasteric artery, pampiniform plexus, genital branch of genitofemoral nerve, and extraperitoneal fat.

What additional contents are found in the female Inguinal Canal?

Round ligament of the uterus.

What is an abdominal hernia?

An abnormal protrusion of a structure through tissues that normally contain it.

Where are abdominal hernias most commonly found?

Inguinal, femoral, umbilical, and epigastric regions.

What is an Indirect Inguinal Hernia?

A hernia where abdominal structures protrude through the inguinal canal, passing through deep and superficial rings, and is more common in young males.

What predisposes someone to an Indirect Inguinal Hernia?

Embryological descent of the testis with persistent processus vaginalis.

How does an Indirect Inguinal Hernia relate to the inferior epigastric vessels?

It is lateral to the neck of the hernia sac.

What is a Direct Inguinal Hernia?

A hernia that occurs due to weakness or defect of the transversalis fascia, placed over the body of the pubis without passing through the deep ring.

How does a Direct Inguinal Hernia relate to the inferior epigastric vessels?

It is medial to the neck of the hernia sac.

What is a Femoral Hernia?

A hernia located below and lateral to the pubic tubercle, more common in females.

What anatomical features minimize herniation in the inguinal region?

Obliquity of the canal, strong anterior and posterior walls, compression during abdominal muscle contraction, and the cremasteric muscle action.

What is the Peritoneum?

A continuous, transparent serous membrane lining the abdominopelvic cavity and investing viscera.

What are the two layers of the Peritoneum?

Parietal Peritoneum, which lines the abdominopelvic wall & diaphragm, and Visceral Peritoneum, which lines the outer surface of most viscera.

What is the function of the mesothelium in the Peritoneum?

It secretes serous fluid for lubrication.

What is Ascites?

An abnormal collection of free fluid in the peritoneal cavity.

What is Paracentesis Abdominis?

A procedure for draining ascitic fluid.

What is a potential pathway of infection in females related to the Peritoneum?

Communication with the exterior through the uterine tubes.

What is the mesentery?

A double layer of peritoneum that invaginates by an organ, providing neurovascular communications and containing connective tissue, vessels, nerves, and fat.

What is the significance of the small intestine mesentery?

It is specifically known as 'the mesentery'.

What is the greater omentum?

A 4-layered peritoneal fold that hangs like an apron from the greater curvature of the stomach and limits infection spread by moving to sites of infection.

What does the lesser omentum connect?

It connects the lesser curvature of the stomach and proximal duodenum to the liver.

What is contained in the free edge of the lesser omentum?

The portal triad, which includes the portal vein, common bile duct, and hepatic artery.

What are peritoneal ligaments?

Double layers of peritoneum connecting organs to other organs or to the abdominal wall.

Name two examples of peritoneal ligaments.

Falciform ligament and hepatoduodenal ligament.

What are peritoneal folds?

Reflections of peritoneum raised by underlying vessels, ducts, or obliterated fetal vessels.

What are peritoneal recesses/fossae?

Blind pouches of peritoneum that are potential sites for hernia or strangulation of the intestine and can spread pathological fluid.

What are the compartments of the abdominal cavity?

The transverse mesocolon divides the cavity into supracolic and infracolic compartments.

What does the supracolic compartment contain?

The stomach, liver, and spleen.

What is Morrison's pouch?

The commonest site of subphrenic abscess and accumulation of fluid or pus, located in the right subhepatic space.

What does the infracolic compartment contain?

The small intestine and ascending/descending colon.

What are paracolic gutters?

Grooves allowing free communication between supracolic and infracolic compartments.

What are the two divisions of the peritoneal cavity?

The greater sac (main part) and the lesser sac (omental bursa).

Where is the lesser sac located?

It lies posterior to the stomach and lesser omentum, allowing free movement of the stomach.

What is the omental foramen?

A communication between the greater sac and the omental bursa, located posterior to the free edge of the lesser omentum.

What is the rectouterine pouch of Douglas?

The most dependent part of the peritoneal cavity in standing position and of the pelvic cavity in supine position in females.

What are intraperitoneal organs?

Organs almost completely covered with visceral peritoneum, such as the stomach, liver, and spleen.

What are secondary retroperitoneal organs?

Organs that were originally intraperitoneal but adhered to the abdominal wall during development, like the duodenum and pancreas.

What are primary retroperitoneal organs?

Organs that lie between the parietal peritoneum and the posterior abdominal wall, having parietal peritoneum only on their anterior surfaces, such as the kidneys and ureters.

What is the length of the esophagus?

25-30 cm long.

Where does the abdominal part of the esophagus end?

At the cardial orifice of the stomach at T11.

What is the narrowest point of the esophagus?

The cervical constriction at C6.

What anatomical structures cause the thoracic constriction of the esophagus?

The aortic arch (T4) and left main bronchus (T5/T6).

Where does the esophagus pass through the diaphragm?

At the esophageal hiatus (T10).

What are the arterial supplies to the abdominal part of the esophagus?

Left gastric artery (from coeliac trunk) and left inferior phrenic artery.

How does the venous drainage of the abdominal part of the esophagus occur?

It drains into the azygos vein and left gastric vein.

What lymph nodes are involved in the lymphatic drainage of the esophagus?

Left gastric nodes and coeliac nodes.