Anatomy Quiz on Abdominal Organs

Abdominal Cavity Organs

• The abdominal cavity is bounded by the abdominal walls, diaphragm, and pelvis
• The abdominopelvic cavity combines the abdominal and pelvic cavities, which are continuous
• The abdominal cavity contains most digestive organs, the spleen, kidneys, and ureters

Digestive Tract

• The abdominal viscera make up most of the digestive tract.
• The esophagus, stomach, liver, gallbladder, duodenum, jejunum, ileum, pancreas, transverse colon, ascending colon, descending colon, sigmoid colon, rectum, and anal canal are all part of the digestive tract.

Abdominal Quadrants

• The abdomen is divided into four quadrants by imaginary horizontal and vertical lines that cross at the umbilicus.
• Right Upper Quadrant (RUQ): Liver, Gallbladder, Pylorus, Duodenum, Hepatic flexure of colon, Head of pancreas.
• Left Upper Quadrant (LUQ): Spleen, Splenic flexure of colon, Stomach, Body & Tail of pancreas.
• Right Lower Quadrant (RLQ): Terminal ileum, Cecum, Appendix, Ascending colon, Right ovary.
• Left Lower Quadrant (LLQ): Descending colon, Sigmoid colon, Left ovary.

Abdominal Regions

• The abdomen can be divided into 9 regions:
• Epigastric
• Right Hypochondriac
• Left Hypochondriac
• Umbilical
• Right Lumbar
• Left Lumbar
• Hypogastric/Suprapubic
• Right Iliac/Inguinal
• Left Iliac/Inguinal

Peritoneum

• Parietal peritoneum lines the inside of the abdominopelvic cavity
• Visceral peritoneum covers the viscera, continuous with the parietal peritoneum
• Peritoneal cavity is the space between visceral and parietal peritoneum
  • Contains ~50 mL of peritoneal fluid
  • Closed in males, but has openings for female oocytes to pass from ovaries to fallopian tubes

Mesenteries

• Mesentery: A double layer of peritoneum that surrounds an organ and connects it to the abdominal wall
  • Provides pathways for nerves, vessels, and lymphatics

Peritoneum Ligaments

• Peritoneal ligaments: double layers of peritoneum that connect organs to each other or to the abdominal wall

Intraperitoneal vs. Retroperitoneal Organs

• Retroperitoneal organs: partially within, but primarily outside the peritoneal cavity (e.g., kidneys)
• Intraperitoneal organs: completely surrounded by peritoneum and within the peritoneal cavity (e.g., stomach)

Intraperitoneal Organs

• Organs enveloped in visceral peritoneum and connected to the abdominal wall by mesentery
• Liver
• Tail of pancreas
• Spleen
• Stomach
• Duodenum (1st part)
• Jejunum & Ileum
• Cecum
• Appendix
• Sigmoid colon
• Upper 1/3 of rectum

Retroperitoneal Organs

• Organs covered with parietal peritoneum on the anterior surface only
• Suprarenal glands
• Aorta/IVC
• Duodenum (2nd, 3rd, 4th parts)
• Pancreas (except tail)
• Ureters
• Colon (Ascending & Descending)
• Kidneys
• Esophagus
• Rectum

Liver

• Detoxifies substances
• Stores glycogen
• Produces hormones
• Synthesizes plasma proteins
• Produces bile
• Divided into 4 anatomical lobes: right, left, quadrate, and caudate
• Has a bare area that is in direct contact with the diaphragm

Liver Ligaments

• Anterior and posterior coronary ligaments
• Right and left triangular ligaments
• Falciform ligament
• Round ligament (ligamentum teres hepatis)

Hepatic Portal Vein

• 75-80% of blood coming from the GI tract goes to the liver through the hepatic portal vein.
• Formed by the union of the superior mesenteric vein and splenic vein,
• Terminates by branching to right and left.

Caval Venous System

• Drains venous blood from structures of posterior abdominal wall, kidneys, adrenal glands, gonads, pelvic structures, and lower limbs
• Blood bypasses the liver to enter the right atrium of the heart.
• Formed by the union of the left and right common iliac veins, and located posterior to the liver

Portal-Caval Anastomoses

• Anastomses between portal & caval veins help with circulation when there is liver/portal vein obstruction.
• Anastomoses occur throughout abdomen, including esophageal, superior/inferior rectal and paraumbilical veins.

Stomach

• The stomach stores food and initiates digestion.
• Divided into 4 regions:
  • Cardia
  • Fundus
  • Body
  • Pylorus

Stomach Ligaments

• Greater omentum: This double-layer peritoneum hangs off of the greater curvature(outer side) of the stomach.
  • Gastrosplenic ligament
  • Gastrophrenic ligament
  • Gastrocolic ligament
• Lesser omentum: This double-layer peritoneum runs to the Lesser curvature (inner side) of the stomach and attaches to the liver.
  • Hepatogastric ligament
  • Hepatoduodenal ligament

Small Intestine

• The small intestine is where most nutrient absorption occurs.
  • Divided into 3 sections: duodenum, jejunum, and ileum
• Duodenum: C-shaped, short (~1 ft)
• Jejunum: ~8 feet
• Ileum: ~12 feet

Small Intestine: Duodenum

• Superior part: short, mostly horizontal, anterolateral to body of L1
• Descending part: runs vertically along sides of L2 & L3, curves around head of pancreas, contains major duodenal papilla
• Inferior part: horizontal, crosses anterior to IVC & aorta, posterior to superior mesenteric artery (at level L3)
• Ascending part: begins to the left of L3

Jejunum & Ileum

• Jejunum: Primarily in the LUQ
• Ileum: Primarily in the RLQ

Jejunum vs. Ileum

• Features: plicae circulares, arterial arcades, and vasa recta are more pronounced in the jejunum.

Small Intestine: Mesentery

• Mesentery proper: a fan-shaped peritoneum that attaches the jejunum & ileum to the posterior abdominal wall

Pancreas

• Accessory digestive gland; posterior to stomach and between the duodenum & spleen
• Produces exocrine (pancreatic juice) & endocrine secretions (glucagon & insulin)
• Divided into: head, neck, body, tail

Pancreas: Ducts

• Main pancreatic duct merges with the common bile duct to form the hepatopancreatic ampulla
• Opens into descending duodenum at the major duodenal papilla
  • Accessory pancreatic duct(accessory duct): also found.

Large Intestine

• Absorbs water & electrolytes, produces and absorbs vitamins, & propels feces
• Includes: cecum (with appendix), ascending colon, transverse colon, descending colon, sigmoid colon, rectum, anal canal

Large Intestine characteristics

• Omental (epiploic) appendices
• Teniae coli
• Haustra

Kidneys

• Remove excess water, salts, and wastes from blood
• Lie retroperitoneally on posterior abdominal wall
• Located on either side of the vertebral column at the level of T12 - L3, Left is slightly higher
• Surrounded by a multilayered capsule including: Fibrous capsule, Perinephric fat, Renal fascia

Blood Supply (General)

• Foregut: esophagus, stomach, liver, gallbladder, pancreas, upper duodenum (supplied by celiac trunk)
• Midgut: lower duodenum, jejunum, ileum, cecum, appendix, ascending colon, proximal 2/3 of the transverse colon (supplied by superior mesenteric artery)
• Hindgut: distal 1/3 of the transverse colon, descending colon, sigmoid colon, rectum, upper anal canal (supplied by inferior mesenteric artery)

Celiac Trunk

• Arises from abdominal aorta at T12
• Branches include: left gastric artery, splenic artery, and common hepatic artery.

Superior Mesenteric Artery

• Arise from abdominal aorta at L1
• Branches supply the midgut including the: ileocolic artery, right colic artery, middle colic artery, intestinal arteries.

Inferior Mesenteric Artery

• Arise from abdominal aorta at L3
• Branches include: left colic artery, sigmoid arteries, superior rectal artery.

Abdominal Veins

• The veins of the abdomen drain blood from different parts of the gut including the foregut, midgut & hindgut.

Innervation (General)

• Sympathetic
  • Inhibits peristalsis
  • Constrict blood vessels in the GI tract
  • Contracts internal anal sphincter
  • Promotes breakdown of glycogen to glucose
  • Parasympathetic
    • Promotes peristalsis
    • Secretion of digestive juices
    • Inhibits internal anal sphincter muscles
    • Promotes building/conservation of glycogen
    • Increases bile secretion

Autonomic Nervous System/Plexuses

• Sympathetic & parasympathetic efferent and afferent fibers innervate abdominal viscera.
  • Sympathetic: arises from T1-L2 spinal cord levels
  • Parasympathetic: arises from cranial nerves (III, VII, IX, X) and S2-S4 spinal cord levels
  • Ganglia: parasympathetic ganglia near or within the walls of target organs; sympathetic ganglia prevertebral & paravertebral.

Splanchnic Nerves

• Splanchnic nerves are paired nerves that carry both visceral efferent (autonomic) & visceral afferent fibers.
  • Sympathetics: Cardiopulmonary, etc.
  • Parasympathetics: Pelvic

Parasympathetic Nervous System

• The nerve nuclei involved in parasympathetic innervation of the abdomen, are found brainstem cranial nerve nuclei (III, VII, IX, X) and within sacral spinal cord levels (S2-S4).
  • CN X (vagus nerve) is the primary parasympathetic nerve innervating the foregut and midgut portions of the gut system
  • Pelvic splanchnic nerves carry the parasympathetic fibers for hindgut and pelvic viscera