Anatomy and Blood Supply of the Abdomen

• The abdomen is the region of the body between the thorax and the pelvis
• It contains several vital organs, including the stomach, small intestine, large intestine, liver, gallbladder, pancreas, spleen, kidneys, and adrenal glands
• The abdominal wall is composed of skin, fascia, muscles, and the parietal peritoneum
• The abdominal cavity is lined by the parietal peritoneum
• The visceral peritoneum covers the abdominal organs

Blood Supply

• The abdominal organs receive blood supply from the abdominal aorta and its branches
• The celiac artery supplies the stomach, liver, spleen, and part of the pancreas and duodenum
• The superior mesenteric artery supplies the small intestine (except the duodenum) and part of the large intestine
• The inferior mesenteric artery supplies the distal part of the large intestine and the rectum
• Venous drainage from the abdominal organs is primarily through the portal venous system, which drains into the liver
• The hepatic veins then drain blood from the liver into the inferior vena cava

Muscular Structure

• The abdominal wall consists of several muscles
  • Rectus abdominis flexes the vertebral column
  • External oblique flexes and rotates the vertebral column
  • Internal oblique flexes and rotates the vertebral column
  • Transversus abdominis compresses the abdomen
• These muscles support and protect the abdominal organs
• They also play a role in respiration, posture, and movements of the trunk

Organ Functions

• Stomach:
  • Stores food
  • Mixes food with gastric juices
  • Begins the digestion of proteins
• Small intestine:
  • Completes the digestion of carbohydrates, proteins, and fats
  • Absorbs nutrients
• Large intestine:
  • Absorbs water and electrolytes
  • Forms and stores feces
• Liver:
  • Produces bile
  • Metabolizes carbohydrates, proteins, and fats
  • Detoxifies harmful substances
  • Stores glycogen, vitamins, and minerals
• Gallbladder:
  • Stores and concentrates bile
• Pancreas:
  • Produces digestive enzymes
  • Secretes insulin and glucagon to regulate blood sugar levels
• Spleen:
  • Filters blood
  • Stores and produces lymphocytes
  • Destroys old or damaged red blood cells
• Kidneys:
  • Filter blood and produce urine
  • Regulate blood pressure and electrolyte balance
• Adrenal glands:
  • Produce hormones such as cortisol, aldosterone, and adrenaline

Common Disorders

• Appendicitis: Inflammation of the appendix, often requiring surgical removal
• Peptic ulcers: Sores in the lining of the stomach or duodenum, often caused by bacterial infection or NSAID use
• Gallstones: Hard deposits in the gallbladder, which can cause pain and inflammation
• Liver cirrhosis: Scarring of the liver, often caused by chronic alcohol abuse or hepatitis
• Pancreatitis: Inflammation of the pancreas, which can be acute or chronic
• Irritable bowel syndrome (IBS): A common disorder that affects the large intestine, causing abdominal pain, bloating, and changes in bowel habits
• Inflammatory bowel disease (IBD): Chronic inflammation of the digestive tract, including Crohn's disease and ulcerative colitis
• Hernias: Protrusion of an organ or tissue through a weak spot in the abdominal wall
• Kidney stones: Hard deposits in the kidneys, which can cause severe pain
• Urinary tract infections (UTIs): Infections of the bladder, urethra, or kidneys

Nervous System

• The abdomen receives innervation from both the somatic and autonomic nervous systems
• The somatic nervous system controls the voluntary muscles of the abdominal wall and provides sensory innervation from the skin
• The autonomic nervous system controls the involuntary functions of the abdominal organs
• The sympathetic nervous system generally inhibits digestive activity and increases blood flow to muscles
• The parasympathetic nervous system generally stimulates digestive activity and decreases heart rate
• The vagus nerve (cranial nerve X) provides parasympathetic innervation to most of the abdominal organs
• The splanchnic nerves carry sympathetic fibers to the abdominal organs
• Pain sensation from the abdominal organs is often referred to other areas of the body due to shared nerve pathways