Biology Chapter 20: The Heart

The heart is located in the mediastinum, a region within the thoracic cavity.

Reduces friction between the pericardial membranes during heart contractions.

Another name for visceral pericardium is epicardium.

The myocardium forms the bulk of the heart wall.

Blood vessels enter and exit the heart at the base.

The coronary sulcus divides the atria and ventricles of the heart.

Blood in the pulmonary veins returns to the left atrium.

Cardiac veins empty into the coronary sinus, which then empties into the right atrium.

The aorta is the major artery that carries oxygenated blood from the left ventricle to the rest of the body.

The right side of the heart pumps deoxygenated blood to the lungs for oxygenation.

Papillary muscles contract to prevent the atrioventricular (AV) valves from prolapsing into the atria during ventricular contraction.

Blood from the superior vena cava flows into the right atrium of the heart.

Blood flows directly from the right ventricle into the pulmonary trunk.

The right ventricle connects to the pulmonary trunk, which carries blood to the lungs.

The sinoatrial (SA) node is the pacemaker of the heart, initiating and controlling the heart's rhythm.

The correct sequence for action potential conduction is: SA node, AV node, AV bundle, bundle branches, Purkinje fibers.

The AV node takes over as the pacemaker if the SA node fails, setting a slower heart rate.

The absolute refractory period is the timeframe during which the myocardium is completely unresponsive to any stimulus, regardless of its strength.

The QRS complex on an ECG represents ventricular depolarization, the electrical impulse that causes ventricular contraction.

The P wave in an ECG represents atrial depolarization, the electrical signal that triggers atrial contraction.

Ventricular systole refers to the contraction phase of the ventricles, during which blood is ejected from the heart.

During the ejection phase, blood is forcefully pumped out of the left ventricle through the aorta.

The first and second heart sounds are produced by the vibrations that occur when the heart valves close, signaling the beginning and end of each heartbeat.

An incompetent mitral valve allows blood to leak back into the left atrium from the left ventricle during ventricular systole.

Arteries have thicker walls than veins, especially the tunica media, which is responsible for muscle and elasticity.

The vasa vasorum are a network of tiny blood vessels that supply nutrients to the walls of larger arteries and veins.

Sympathetic nerve fibers innervating blood vessels primarily reside in the tunica media, the middle layer.

Arteriosclerosis involves the thickening of the tunica intima and loss of elasticity in the tunica media.

The subclavian, axillary, and brachial arteries form a continuous pathway supplying blood to the upper limb.

The celiac artery branches to supply the stomach and liver.

The brachiocephalic artery, left common carotid artery, and left subclavian artery directly branch from the aortic arch.

The abdominal aorta splits at L5 into two common iliac arteries, supplying the lower limbs.

The spleen can store a significant amount of blood, acting as a reservoir that can be released into circulation if needed.

Innate immunity provides a general, non-specific defense against pathogens, initiating the same response regardless of the specific pathogen encountered.

Complement proteins can directly attack pathogens by forming holes in their membranes, leading to their destruction.

Lysozyme is an enzyme found in bodily fluids that breaks down the cell walls of certain bacteria, hindering their growth.

Neutrophils are typically the first immune cells to leave the bloodstream and migrate to infected tissues, where they combat invading pathogens.

The inflammatory response aims to prevent the spread of infection by containing the invading pathogens and promoting healing.

Histamine, prostaglandins, and leukotrienes are chemicals released during inflammation, leading to increased blood vessel permeability, chemotaxis, and vasodilation.

Chemotaxis refers to the movement of leukocytes towards specific chemicals released during inflammation, guiding them to the site of infection.

The low pH (acidic environment) of the stomach is crucial for activating pepsin, an enzyme vital for protein digestion.

The enterogastric reflex, which slows down gastric emptying, can be triggered by several factors, including distention of the duodenal wall (stretching of the small intestine), the presence of food in the stomach, and increased pH in the duodenum (less acidic environment).

Chyme is the semiliquid mixture formed in the stomach from the breakdown of food by gastric juices.

The pyloric pump is a muscular action that controls the movement of chyme from the stomach into the small intestine through the partially closed pyloric opening.

The small intestine secretes various enzymes, including disaccharidases, which break down disaccharides into simpler sugars.

Pepsinogen, a precursor to the digestive enzyme pepsin, is activated in the stomach by the acidic environment (low pH).

Villi, microvilli, and plicae circulares are finger-like projections in the small intestine that significantly increase the surface area for absorption of nutrients.

The hepatopancreatic ampulla is formed by the union of the common bile duct (carrying bile from the liver) and the pancreatic duct (carrying pancreatic juice).