Exam 3 Review:  Chapter 23:  Liver Anatomy

liver - The large, reddish-brown, glandular digestive organ located in the upper right quadrant of the abdominal cavity beneath the diaphragm which is divided into three lobes, the right, left, and caudate; it synthesizes and secretes bile, is active in the formation of certain blood proteins and lipoproteins; plays a major role in the metabolism of carbohydrates, fats, and proteins; stores or detoxifies toxins; it receives blood from both the hepatic artery and the hepatic portal system.

liver lobes - The three major anatomical divisions of the liver; the right, left, and caudate lobes, which are separated by fissures and connective tissue ligaments.

falciform ligament - The anteroposterior fold of the parietal peritoneum attached to the under surface of the diaphragm and the sheath of the rectus muscle and along a line on the anterior and upper surfaces of the liver extending back from the notch on the anterior margin of the liver; it is a main support for the liver in the abdominal cavity.

ligamentum teres - A dense fibrous connective tissue cord resulting from the obliteration of the umbilical vein of the fetus and passing from the navel to the notch in the anterior border of the liver and along the undersurface of that organ.

coronary ligaments - Several folds of the parietal peritoneum attached to the under surface of the diaphragm and to the liver; they are supports for the liver in the abdominal cavity.

lobules - Small sections or subdivisions of the lobe of an organ; in the liver, the structural subunit which consists of roughly hexagonal arrangements of plates or cords of hepatocytes radiating outward from a central vein and separated from each other by radiating capillary sinusoids; each lobule is surrounded by a thin layer of dense fibrous connective tissue; the liver contains ~1,000,000 lobules.

central vein - The single large blood vessel in the middle of each lobule of the liver which runs from the apex to the base of the lobule, receives blood from the sinusoids, and empties into the sublobular veins from where the blood will eventually return to the inferior vena cava.

hepatocytes - The parenchymal (chief functional) cells of the liver organized into plates or cords radiating outward from the central vein of each liver lobule and separated from each other by radiating capillary sinusoids; they are polygonal in shape with a large oval nucleus and a granular cytoplasm; they carry out a wide variety of metabolic, endocrine, and secretory (exocrine) functions; they synthesize and secrete bile, synthesize and secrete certain blood proteins and lipoproteins; play a major role in the metabolism of carbohydrates, fats, and proteins; store or detoxify toxins, etc.

portal triad - A characteristic histological feature of the borders of liver lobules, consisting of one or more of each of the following structures, a branch of the hepatic artery bringing oxygenated blood to the hepatocytes, a branch of the hepatic portal vein bringing nutrient laden blood from the capillary beds of the stomach, small and large intestines, spleen, and pancreas, and an interlobar branch of the bile duct system.

sinusoid (capillary)  - The category of capillaries, primarily the capillaries in the liver, bone marrow, some endocrine glands and in lymphoid tissue, which lack pores = fenestrations but in which adjacent endothelial cells exhibit some wider intercellular gaps which permit some fluid exchange between the plasma and the tissue fluid by transfer between endothelial cells; they often have an irregular cross-section.

stellate reticuloendothelial cells - The fixed macrophages of the walls of the liver sinusoids which have long cytoplasmic projections, a large oval nucleus and their cytoplasm is commonly packed with fragments resulting from phagocytic action; they play a major role, along with the spleen, in clearing the blood of damaged RBCs and in removing immune (Ab-Ag) complexes from the blood.  aka - Kupffer cells

hepatic portal* circulation = hepatic portal* system - The separate pathway for a portion of the blood returned to the heart from certain the abdominal organs; the vessels involved are the hepatic portal vein and its branches (splenic vein, superior and inferior mesenteric veins and gastric vein and their smaller branches); venous blood from the capillary beds of the spleen, pancreas, stomach and intestines (large and small) is routed to the capillary beds of the liver where various compounds in the blood are processed or stored by the liver; after leaving the liver this blood is returned to the general venous return of the inferior vena cava.  [Note:  A portal system is a vascular arrangement in which blood from the capillaries of one organ is transported to the capillaries of another organ by a connecting vein or veins without returning to the heart.]

hepatic portal vein - The large blood vessel carrying blood from the capillary beds of the spleen, pancreas, stomach and intestines (large and small) to the liver where the nutrients carried by the blood are processed by the hepatocytes before passing into the systemic circulation.

enterohepatic circulation - A circular pathway in which molecules, particularly bile salts and bile acids, are recycled; the path is from the liver to the small intestine via the biliary tree, reabsorption from the chyme in the intestines into the hepatic portal circulation, and back to the liver.

List:

10.  the five organs whose venous blood is routed by the hepatic portal system to the liver and a reason why each of these organs has its venous blood routed to the liver.

Organ Reason(s) For Routing The Organ's Venous Blood To The Liver
Stomach (1) absorbed nutrients (minimal) will be processed and stored by the liver
(2) absorbed toxins (including ethanol and various other lipid-soluble drugs) can be detoxified, modified or stored by the liver
Small Intestine (1) absorbed nutrients (minimal) will be processed and stored by the liver
(2) absorbed toxins (including ethanol and various other lipid-soluble drugs) can be detoxified, modified or stored by the liver
Large Intestine (1) absorbed nutrients (minimal) will be processed and stored by the liver
(2) absorbed toxins (including ethanol and various other lipid-soluble drugs) can be detoxified, modified or stored by the liver
Pancreas insulin and glucagon, which have major regulatory control of carbohydrate metabolism by the liver can be routed directly to the liver to exert their control
Spleen bilirubin, derived from the heme groups of worn-out or damaged red blood cells, can be routed directly to the liver for further modification and excretion into the bile

Diagram and Label:

2. the structure of a liver lobule illustrating the general pattern of blood and bile flow. Identify the factors that increase bile secretion by the liver.

Blood Flow:  Oxygenated blood from the systemic circulation via the abdominal aorta and hepatic artery and deoxygenated blood from the stomach, small intestines, large intestine, pancreas, and spleen are delivered to the periphery of each liver lobule (at hepatic = portal triads); mix in the capillary sinusoids of the liver lobule and drain to the central vein which carries the hepatic venous blood out of the liver via the hepatic veins, then to the inferior vena cava and from there back to the right atrium of the heart.
Bile Flow:  Bile is synthesized by hepatocytes and secreted into bile canaliculi which drain away from the central vein and toward the periphery of each liver lobule (at hepatic = portal triads) where the bile is passed into the smaller vessels of the biliary tree and routed out of the liver via the common hepatic duct.
As chyme is passed from the pylorus to the duodenum, stretch receptors and chemoreceptors are stimulated.  (1) This sensory information is routed as visceral sensory information to the CNS and an autonomic reflex involving parasympathetic impulses carried on the Vagus Nerve (X) stimulate bile production by the liver and bile secretion from the gall bladder.  (2) This sensory information also influences intestinal enteroendocrine cells to release (a) secretin which is carried by hepatic portal drainage to the liver to stimulate bile production by the liver and (b) cholecystokinin (CCK) which is carried by hepatic portal drainage to the liver to stimulate bile secretion from the gall bladder.