Hemostasis, Clotting, and Thrombosis

• Hemostasis involves three phases that prevent blood loss from damaged vessels.

Hemostasis Phases

• Vascular spasm constricts blood vessels, limiting blood leakage from the injury.
• Platelet plug formation occurs when platelets adhere to exposed collagen, forming a temporary plug.
• Coagulation transforms blood into a gel through a fibrin mesh, reinforcing the plug.

Clot Breakdown (Fibrinolysis)

• Fibrinolysis dissolves blood clots utilizing plasmin.
• Plasminogen, an inactive enzyme, converts to plasmin by activators to initiate clot breakdown.
• Plasmin breaks down fibrin into smaller fragments.
• Macrophages then remove these fibrin fragments.

Undesirable Clotting (Thrombosis)

• Thrombus refers to a stationary clot within a blood vessel.
• Embolus describes a clot that travels in the bloodstream and can obstruct vessels.
• Thrombosis can lead to conditions such as deep vein thrombosis (DVT), pulmonary embolism (PE), stroke, and heart attack.
• Causes of undesirable clotting include blood stasis, hypercoagulability, and endothelial injury.
• Prevention and treatment involve medications (blood thinners), lifestyle adjustments, and compression therapy.

Digestive System

• The digestive system is comprised of the GI tract and accessory organs.
• Organs include the mouth, teeth, saliva, esophagus, stomach, small intestine, liver, gallbladder, pancreas, and large intestine.

Digestive Processes

• Ingestion involves the intake of food.
• Propulsion moves food along the GI tract.
• Mechanical digestion breaks food into smaller pieces.
• Chemical digestion breaks down food molecules with enzymes.
• Absorption transports nutrients into the blood or lymph.
• Excretion removes undigested waste.

Function of Bile

• Bile is a digestive fluid produced by the liver and stored in the gallbladder, playing a crucial role in fat digestion and absorption.
• Bile emulsifies fats by breaking large globules into smaller droplets using bile salts, increasing surface area for pancreatic lipase.
• The emulsification process enhances the digestion and absorption of dietary fats.
• Bile aids in fat absorption through the creation of micelles.
• Micelles are tiny fat droplets surrounded by bile salts that transport fats to the intestinal lining for absorption.
• Bile contains bilirubin, a byproduct of red blood cell breakdown, which gives feces its brown color.
• Bile helps eliminate cholesterol and toxins from the body.
• Bile is slightly alkaline and helps neutralize stomach acid in the small intestine, creating a suitable pH for pancreatic enzymes.
• Bile aids in the absorption of fat-soluble vitamins (A, D, E, K) by dissolving them in micelles for transport across the intestinal lining.
• Bile is released when fatty food enters the duodenum.
• Cholecystokinin (CCK) signals the gallbladder to release bile into the bile duct, which empties into the small intestine.

Hepatic Blood Flow

• The liver receives blood from the hepatic artery and the hepatic portal vein.
• The hepatic artery supplies oxygenated blood from the heart, accounting for about 25% of the liver’s blood supply.
• The hepatic portal vein supplies nutrient-rich, deoxygenated blood from the digestive organs, accounting for about 75% of the liver’s blood supply.
• Blood exits the liver through the hepatic veins into the inferior vena cava, which returns blood to the heart.

Pathway of Hepatic Blood Flow

• The hepatic artery branches from the celiac trunk and delivers oxygen-rich blood to hepatocytes
• The hepatic portal vein forms from the union of the superior mesenteric vein and the splenic vein.
• The hepatic portal vein carries nutrients, toxins, and hormones from the digestive tract for processing in the liver.
• Liver sinusoids are capillary-like structures in the liver where hepatic artery and portal vein blood mix.
• Kupffer cells (liver macrophages) in the sinusoids remove bacteria and toxins.
• Hepatocytes process nutrients, detoxify chemicals, and produce bile in the sinusoids.
• Processed blood drains into central veins, which merge into hepatic veins, and then empty into the inferior vena cava, returning blood to the heart.

Functions of Hepatic Blood Flow

• Nutrient processing regulates glucose, amino acids, and lipids.
• Detoxification removes drugs, alcohol, and toxins from the blood.
• Immune function involves Kupffer cells filtering pathogens.
• Bile production aids in digesting fats and removing waste.

Explore the three phases of hemostasis: vascular spasm, platelet plug formation, and coagulation. Learn about clot breakdown via fibrinolysis using plasmin, and understand the risks and causes of undesirable clotting (thrombosis), including DVT and PE.