Blood, Vessels, Heart Anatomy Final Study Guide PDF

Main Components of Blood - (37-54% of blood is RBC, WBC, and platelets Carries O2 and some CO2 Defends against toxins and pathogens) ​ Fluid CT, located within veins, arteries, capillaries, and organs, (e.g., heart and spleen) ​ Men have on average 5-6 L and women have 4-5 L of blood...

Main Components of Blood - (37-54% of blood is RBC, WBC, and platelets Carries O2 and some CO2 Defends against toxins and pathogens) ​ Fluid CT, located within veins, arteries, capillaries, and organs, (e.g., heart and spleen) ​ Men have on average 5-6 L and women have 4-5 L of blood ​ Red Blood Cells ​ White Blood Cells ​ Platelets ​ Plasma is 37-54% of blood, transports plasma proteins, electrolytes ​ key functions include of Blood - ○​ Transportation of dissolved gasses, nutrients, hormones, enzymes, metabolic wastes, etc ○​ Buffering and regulation of pH, temperature, osmolarity ○​ Defense against toxins, pathogens, and dead/damaged body tissue ○​ Clotting Red Blood Cell Structure - Benefit of this structure: ​ Permits rapid diffusion ​ Strong and flexible ​ Stacks easily ​ RBC have very few organelles, Therefore, damage cannot be fixed and lifespan is short Hemoglobin - ​ Primary protein of red blood cells that carries oxygen and some CO2 ​ Protein is called a Globular protein ​ Made up of four polypeptide chains (2 alpha 2 beta chains) ​ Each chain contains a heme group, which includes an iron (Fe²⁺) ion that can bind to one molecule of oxygen (O₂) ​ Function: Hemoglobin is essential for carrying oxygen from the lungs to tissues and facilitating the transport of carbon dioxide from tissues back to the lungs Oxyhemoglobin VS Carbaminohemoglobin - ​ Oxyhemoglobin: Hemoglobin bound to oxygen. ​ Formation: Forms when oxygen binds to the iron (Fe²⁺) in the heme group of hemoglobin in the lungs. ​ Function: Transports oxygen from the lungs to tissues. ​ Color: Bright red, giving oxygen-rich blood its characteristic color ​ Carbaminohemoglobin: Hemoglobin bound to carbon dioxide (CO₂). ​ Formation: Forms when carbon dioxide binds to the amino groups of the globin (protein) part of hemoglobin in tissues. ​ Function: Transports about 20-30% of carbon dioxide from tissues back to the lungs for exhalation. ​ Color: Darker red, contributing to the darker color of deoxygenated blood Pulmonary Circuit - 1.​ Deoxygenated blood enters the right atrium of the heart from the inferior 1.​ Blood flows from the right atrium into the right ventricle through the tricuspid valve. 1.​ The right ventricle pumps deoxygenated blood into the pulmonary trunk during contraction.  2.​ The pulmonary trunk splits into the left and right pulmonary arteries, which carry deoxygenated blood to the lungs. 3.​ In the lungs, the pulmonary arteries branch into lobar arteries, which further divide into smaller arterioles and capillary beds where gas exchange occurs—carbon dioxide is released, and oxygen is absorbed. 1.​ Oxygenated blood returns to the left atrium of the heart via the pulmonary veins. ****In the pulmonary circuit, arteries carry deoxygenated blood to the lungs, while veins carry oxygenated bloodback to the heart. Left Ulnar Vein to left Ulnar Artery - 1.​ Left ulnar vein (in the forearm) carries deoxygenated blood. 2.​ It drains into the left brachial vein. 3.​ The left brachial vein joins the left axillary vein. 4.​ The left axillary vein becomes the left subclavian vein. 5.​ The blood travels to the superior vena cava and enters the right atrium of the heart. 6.​ Blood is pumped from the right ventricle to the lungs for oxygenation. 7.​ Oxygenated blood returns to the left atrium and is pumped to the left ventricle. 8.​ Blood is then pumped from the left ventricle through the aorta. 9.​ The left subclavian artery branches from the aorta. 10.​The left subclavian artery becomes the left axillary artery. 11.​The left axillary artery continues as the left brachial artery. 12.​The left brachial artery divides into the left radial and left ulnar arteries Layers of the Blood Vessels - 1.​ Tunica Externa (Adventitia) ​ Structure: The outermost layer of a blood vessel, made up mostly of dense irregular connective tissue ​ Components: contains collagen fibers (for strength and support) and elastin fibers (for flexibility) ​ Function: This layer anchors the blood vessel to nearby tissues and provides structural support. It also houses blood vessels (called vasa vasorum) that supply the vessel itself with oxygen and nutrients 2. Tunica Media ​ Structure: The middle layer, made up mostly of smooth muscle and elastic fibers ​ Muscle Type: The smooth muscle in this layer allows the vessel to contract (vasoconstriction) or relax (vasodilation), which helps regulate blood pressure and flow ​ Function: The smooth muscle controls the diameter of the blood vessel, allowing the vessel to adjust its size based on the body's needs (e.g., more blood to muscles during exercise) ​ Elastic Fibers allow the vessel to stretch and recoil with each heartbeat, especially in arteries. 3. Tunica Intima  ​ Structure: The innermost layer, which is a thin layer of epithelium that line the lumen (inside) of the vessel ​ Type of Epithelium: It consists of simple squamous epithelium, which provides a smooth surface for blood flow. ​ Function: minimizes friction as blood flows through the vessel Elastic Arteries (e.g., aorta, brachiocephalic trunk, pulmonary trunk) - Function: primary function of elastic arteries is to maintain a steady blood flow despite the intermittent pumping of the heart, and to protect smaller arteries from excessive pressure changes ​ Large lumen (inside of artery) ​ Tolerates high pressure change during cardiac cycle ​ Recoil during diastole (relaxation phase of the heart) to propel blood forward ​ Tunica (the same/normal) ​ Media (more elastic fibers than usual to accommodate for high pressure changes) ​ Intima (thicker than usual to provide additional structural support to withstand high pressure changes) Muscular Arteries (e.g., radial, ulnar, brachial, femoral arteries) - Function: primary function of muscular arteries is to distribute blood efficiently by controlling the volume of blood reaching various organs and tissues through adjustments in the diameter of the vessel ​ Tunica media is thicker, greater amount of smooth muscle and less elastic CT ​ The increased smooth muscle allows muscular arteries to control blood flow through vasoconstriction and vasodilation. ​ The reduced elastic tissue reflects their function of controlling blood distribution rather than handling high-volume, high-pressure fluctuations. ​ The thicker walls are needed for strength and to support the artery’s role in maintaining consistent and directed blood flow ​ Vessel diameter under control of autonomic nervous system ​ Normal Tunica Externa ​ Normal Tunica Intima Arterioles - ​ Innervated by sympathetic nervous system during stress or exercise to prioritize blood flow to critical areas like muscle ​ Also adjust their size based on local needs, e.g., oxygen levels of waste build-up in tissue ​ Regulates blood flow between arteries and capillaries by responding to local conditions, e.g., if tissue needs more oxygen, nutrients, or waste removal ​ Tunica is usual ​ Tunica externa is thinner because arterioles are generally smaller ​ Tunica media has less or "patchy" smooth muscle which allows arterioles to adjust their size based on needs of the tissue Capillaries - ​ Smallest and most delicate vessel ​ Only vessel where nutrients, oxygen, and waste products can move between the blood and surrounding tissues ​ No tunica externa or media ​ Tunica intima is very thin and made of single layer of simple squamous epithelium, their thin walls make it easier for nutrients, oxygen, and waste to pass between the blood and tissue ​ single layer of cells minimizes the distance substances have to travel, speeding up the exchange process Types of Capillaries: 1.​ Continuous Capillaries - ​ Structure: Endothelial cells are tightly connected by tight junctions and have small gaps (intracellular clefts)between cells. ​ Function: Allows exchange of small molecules (like water, ions, and gases) while blocking larger molecules. ​ Location: Found in most tissues, such as the skin, muscles, and lungs 1.​ Fenestrated Capillaries - ​ Structure: Endothelial cells have pores (fenestrations) in addition to intracellular clefts. ​ Function: Permits faster and greater exchange of fluids and small solutes like nutrients and hormones. ​ Location: Found in areas needing rapid exchange, such as the glomerulus in kidneys, intestines, and endocrine glands 1.​ Sinusoid Capillaries - ​ Structure: Have large fenestrations and wide, irregular shapes, allowing even large substances like proteins and cells to pass through. ​ Function: Facilitates the exchange of large molecules, such as proteins and blood cells. ​ Location: Found in the liver, spleen, and bone marrow where large-scale filtering and recycling occur Veins & Venules - Venules: ​ Thin media and externa, usual intima Function: ​ Collect blood from capillaries and transport it to veins. ​ Low-pressure vessels designed to facilitate blood return Veins: ​ Tunica Externa: Thickest layer, composed of dense irregular connective tissue, elastic and collagen fibres, providing structural support ​ Tunica Media: Thin layer of smooth muscle  ​ Lumen (Tunica Intima): Large diameter, allowing veins to store large volumes of blood (about 60-70% of total blood volume) ​ Valves: Present in many veins, especially in limbs, to prevent backflow and ensure one-way blood movement toward the heart Function: ​ Serve as blood reservoirs due to their capacity to hold a significant volume of blood. ​ Return deoxygenated blood to the heart under low pressure Mechanisms of Venous Return (against gravity) - ​ Skeletal m. pump: muscle contractions compress veins, especially in the limbs, pushing blood upward toward the heart. The venous valves prevent backflow, ensuring unidirectional blood flow. This mechanism is particularly effective during physical activity, as muscle contractions increase. ​ Venous valves: Prevent blood from flowing backward ​ Changes in thoracic pressure: assists venous return to the heart by using pressure changes during breathing: during inhalation, the diaphragm contracts, increasing abdominal pressure and decreasing thoracic pressure, creating a gradient that pushes blood from abdominal veins toward the thoracic veins. During exhalation, the diaphragm relaxes, and venous valves prevent backflow, ensuring continuous blood flow toward the heart. This mechanism is vital for moving blood against gravity, particularly from the lower body ​ Think of it like a squeeze toy: when you inhale, the "squeeze" in the abdomen pushes blood upward, and when you exhale, the relaxation allows the next "squeeze" to occur, keeping blood moving in one direction. Precapillary Sphincters - ​ Type of Tissue: Composed of smooth muscle encircling the entrance of capillaries. ​ Microscopic Appearance: Thin, circular muscle layer located at the junction of arterioles and capillaries ​ Function: regulate and distribute blood flow efficiently based on tissue needs Capillaries - ​ Smallest and most delicate vessel ​ Only vessel where nutrients, oxygen, and waste products can move between the blood and surrounding tissues ​ No tunica externa or media ​ Tunica intima is very thin and made of single layer of simple squamous epithelium, their thin walls make it easier for nutrients, oxygen, and waste to pass between the blood and tissue ​ single layer of cells minimizes the distance substances have to travel, speeding up the exchange process Types of Capillaries: 1.​ Continuous Capillaries -  ​ Structure: Endothelial cells are tightly connected by tight junctions and have small gaps (intercellular clefts)between cells. ​ Function: Allows exchange of small molecules (like water, ions, and gases) while blocking larger molecules. ​ Location: Found in most tissues, such as the skin, muscles, and lungs 1.​ Fenestrated Capillaries - ​ Structure: Endothelial cells have pores (fenestrations) in addition to intercellular clefts. ​ Function: Permits faster and greater exchange of fluids and small solutes like nutrients and hormones. ​ Location: Found in areas needing rapid exchange, such as the glomerulus in kidneys, intestines, and endocrine glands 1.​ Sinusoid Capillaries - ​ Structure: Have large fenestrations and wide, irregular shapes, allowing even large substances like proteins and cells to pass through. ​ Function: Facilitates the exchange of large molecules, such as proteins and blood cells. ​ Location: Found in the liver, spleen, and bone marrow where large-scale filtering and recycling occur Muscular Artery VS Muscular Vein - Functional Features: Muscular Artery ​ Role: Distribute oxygenated blood from elastic arteries (e.g., aorta) to smaller arterioles and tissues ​ Pressure: Operates under high pressure due to proximity to the heart ​ Vasoconstriction/Dilation: Smooth muscle regulates blood flow and pressure via vasoconstriction or vasodilation Muscular Vein ​ Role: Return deoxygenated blood from tissues to the heart ​ Pressure: Operates under low pressure ​ Assistance in flow: Valves and surrounding skeletal muscle contractions help propel blood against gravity Structural Features: Muscular Artery ​ Epithelium: Endothelium (simple squamous epithelium) in the tunica intima. ​ Tunica Intima: Contains an internal elastic lamina separating it from the tunica media. ​ Tunica Media: Well-developed, thick, with multiple layers of smooth muscle cells and some elastic fibers. ​ Tunica Externa (Adventitia): Relatively thin compared to the media, composed of connective tissue with collagen and elastic fibers. ​ Lumen Shape: Round and consistent in cross-section due to wall thickness. Muscular Vein  ​ Epithelium: Endothelium (simple squamous epithelium) in the tunica intima. ​ Tunica Intima: No elastic lamina. ​ Tunica Media: Thin, with fewer layers of smooth muscle cells and minimal elastic fibers. ​ Tunica Externa (Adventitia): Dominant layer, thick, composed of connective tissue with collagen fibers. ​ Valves: Present, particularly in veins of the lower limbs, to prevent backflow. ​ Lumen Shape: Irregular or collapsed due to thin walls and low pressure Layers and Spaces of the Pericardial Sac - 1.​ Fibrous Pericardium ​ Tissue: Dense irregular connective tissue. ​ Location: Outermost layer, fused to the diaphragm, chest wall, and great vessels. ​ Function: Provides structural support, anchors the heart in place, and prevents overexpansion of the heart 1.​ Serous Pericardium ○​ Tissue: Continuous double-layered serous membrane Two layers: -​ Parietal Layer of Serous Pericardium ○​ Tissue: Serous membrane. ○​ Location: Fused to the inner surface of the fibrous pericardium. ○​ Function: Produces serous fluid to reduce friction between layers -​ Visceral Layer of Serous Pericardium (Epicardium) ○​ Tissue: Serous membrane that adheres directly to the surface of the heart. ○​ Function: Provides a protective covering for the heart and participates in producing serous fluid 1.​ Pericardial Cavity ○​ Content: Contains serous fluid.  ○​ Function: Acts as a lubricant, reducing friction between the parietal and visceral layers of the serous pericardium during heart movements Understand flow of blood through the heart - 1.​ [start] Deoxygenated blood returns from the body through the superior and inferior vena cava into the right atrium → 2.​ Blood moves from the right atrium to the right ventricle through the tricuspid valve → 3.​ The right ventricle pumps blood through the pulmonary valve into the pulmonary trunk and pulmonary arteries to the lungs for oxygenation → 4.​ Oxygenated blood returns from the lungs to the left atrium via the pulmonary veins → 5.​ Blood flows from the left atrium to the left ventricle through the bicuspid valve → 6.​ The left ventricle pumps oxygenated blood through the aortic valve into the aorta to supply the body [finish] Conducting Pathway - 1.​ SA Node (Sinoatrial Node) ​ Function: Initiates the signal for the heart to contract (pacemaker of the heart) ​ Location: In the right atrium near the superior vena cava 1.​ Internodal Pathways ​ Function: Conducting cells that propagate the electrical signal through both atria to the AV node 1.​ AV Node (Atrioventricular Node) ​ Function: Receives the signal from the atria and causes a brief delay, allowing the atria to fully contract before the ventricles contract ​ Location: In the interatrial septum near the right atrium 1.​ AV Bundle (Bundle of His) ​ Function: Transmits the electrical signal from the AV node to the ventricles ​ Location: Located in the interventricular septum, splits into the right and left bundle branches 1.​ Bundle Branches ​ Function: Carries the electrical impulse down the interventricular septum to the apex of the heart 1.​ Purkinje Fibres ​ Function: Conducting fibres that distribute the electrical impulse to the ventricular myocardium, ensuring coordinated contraction of the ventricles ​ Location: Spread throughout the ventricles Tissue of the Heart - 1. Epicardium (or Visceral Pericardium) ​ Tissue Composition: Loose areolar connective tissue + adipose tissue. ​ Function: ○​ Forms the protective outermost layer of the heart. ○​ Cushions the heart with fat.  ○​ Houses blood vessels and nerves supplying the heart. 2. Myocardium ​ Tissue Composition: ○​ Cardiac muscle cells: Responsible for contraction. ○​ Dense irregular connective tissue (cardiac skeleton): Anchors cardiac muscle fibers and maintains structural integrity. ○​ Blood vessels and nerves: Supply the myocardium with oxygen and nutrients. ​ Function: ○​ Powers the heart's pumping action. ○​ The cardiac skeleton provides structural support, prevents overstretching, and isolates electrical impulses within the heart. 3. Endocardium ​ Tissue Composition: Simple squamous epithelial tissue (endothelium). ​ Function: ○​ Provides a smooth, frictionless lining for the heart chambers and valves. ○​ Minimizes resistance and turbulence in blood flow. ○​ Prevents clot formation through its non-thrombogenic surface. ​ ***Advantage: The thin, smooth surface ensures efficient and uninterrupted blood flow Coronary Arteries - Origins: Coronary arteries arise directly from the aortic sinuses 1.​ Right Coronary Artery (RCA) ○​ Originates from the right aortic sinus (an outpouching in the ascending aorta). 2.​ Left Coronary Artery (LCA) ○​ Originates from the left aortic sinus (also in the ascending aorta). Phase of Maximum Blood Flow: ​ Diastole: Most coronary blood flow occurs during ventricular relaxation (diastole) because: 1.​ During systole, the contraction of the myocardium compresses the coronary vessels, reducing blood flow. 2.​ During diastole, the myocardium relaxes, allowing coronary vessels to dilate and fill with blood Coronary Sinus Function: ​ Collects deoxygenated blood from the heart's myocardium (via the cardiac veins) and returns it to the right atrium. Location: ​ Found on the posterior aspect of the heart, running along the coronary sulcus between the left atrium and left ventricle. ​ Drains into: The right atrium, near the opening of the inferior vena cava Internal Heart Features - (right atrium) ​ Orifices of Superior and Inferior Vena Cava: Entry points for deoxygenated blood from the body into the right atrium ​ Orifice of the Coronary Sinus: Entry for deoxygenated blood from the heart muscle into the right atrium ​ Fossa Ovalis: A remnant of fetal circulation ​ Sites of the Sinoatrial Node (cardiac pacemaker): initiates heartbeat and Atrioventricular node: Receives signal from the SA node and relays it to the ventricles (left atrium) ​ Orifices (usually 4) of the incoming pulmonary veins: Four openings where oxygenated blood from the lungs enters the left atrium (right ventricle) ​ Tricuspid valve (or right atrioventricular valve): Prevents backflow of blood from the right ventricle to the right atrium ​ Opening of the pulmonary trunk with its pulmonary semilunar valve: Allows blood to flow from the right ventricle to the lungs (left ventricle) ​ Bicuspid (or left atrioventricular or mitral) valve with its two cusps: Prevents backflow from the left ventricle to the left atrium ​ Orifice of aorta with its aortic semilunar valve: Directs oxygenated blood from the left ventricle to the body ​ Aorta with its three branches coming off the aortic arch: Brachiocephalic artery - 1st branch: Supplies blood to the right arm and right side of head and neck Left common carotid artery - 2nd branch: Supplies blood to the left side of the head and neck Left subclavian artery - 3rd branch: Supplies blood to the left arm ​ ***Why are the left ventricle walls thicker than the right? → the left ventricle is responsible for pumping blood through the whole systemic circulatory system External Heart Features - ​ Superior & Inferior Vena Cava: Bring deoxygenated blood from the body to the right atrium ​ Aorta: Carries oxygenated blood from the left ventricle to the body ​ Pulmonary Trunk: Transports deoxygenated blood from the right ventricle to the lungs ​ Apex of Heart: The pointed end of the heart, mainly the left ventricle, which helps in pumping blood ​ Right Auricle: Small, ear-like extension of the right atrium that helps hold extra blood ​ Left Auricle: Small, ear-like extension of the left atrium that helps hold extra blood ​ Pericardial Sac:  - composed of the parietal pericardium -Fibrous pericardium: outer layer of dense connective tissue abundant with collagen fibres ​ Coronary Sulcus: surface landmark showing separation between the atria and ventricles ​ Right Coronary Artery - sits in the coronary sulcus on the right side; supplies blood to the right side of the heart muscle ​ Coronary Sinus: an enlarged vessel receiving the deoxygenated blood from the heart muscle and returns it to the right atrium ​ Anterior Interventricular Sulcus: surface landmark showing the separation between the right and left ventricles; arteries and veins lie within it ​ Left Coronary Artery: arises from the aorta and provides the oxygenated blood supply for the heart muscles Cardiac Muscle - Structure: striated, short, centrally placed individual nuclei, and branching cells, intercalated discs and gap junctions connect the cells for synchronized contractions Function: involuntary, with autorhythmic pacemaker cells that maintain a rhythmic heartbeat without nervous stimulation Location: found only within the heart Papillary Muscles: ​ Structure: Cone-shaped projections of cardiac muscle in the ventricular walls. ​ Function: ○​ Contract during ventricular systole (when ventricles contract). ○​ Pull on chordae tendineae to prevent AV valves (tricuspid and mitral) from inverting into atria. ○​ Prevent valve regurgitation (backflow of blood). Chordae Tendineae: ​ Structure: Fibrous connective tissue cords that connect papillary muscles to the edges of AV valve cusps. ○​ Composed of dense connective tissue rich in collagen (strong and flexible). ​ Function: ○​ Act as "tethers" to stabilize valve cusps. ○​ Maintain tension during ventricular contraction, ensuring valve closure and preventing backflow into the atria. Papillary Muscles + Chordae Tendineae Interplay: ​ Work as a unit during ventricular systole: ○​ Papillary muscles contract → chordae tendineae tighten → valve cusps remain securely closed. Key Points: 1.​ Papillary muscles contract only during systole to stabilize AV valves.  2.​ Chordae tendineae prevent valve prolapse by tethering cusps to papillary muscles. 3.​ Damage to either structure → valve regurgitation and potential heart failure Pacemaker and Contractile Cells - ​ Pacemaker cells (e.g., in the Sinoatrial node) generate action potentials that stimulate the heart to beat ​ These cells lack contractile proteins (actin and myosin), which is why they don’t contract like other cardiac muscle cells ​ Atrioventricular node is a secondary pacemaker and The SA node is the primary pacemaker ​ Contractile cells (found in the atria and ventricles) contain the necessary proteins for contraction and are responsible for the mechanical pumping action of the heart Definitions: -​ Systole refers to the phase when the heart contracts (either atrial or ventricular). -​ Diastole refers to the phase when the heart relaxes, allowing chambers to fill with blood Valves Opened or Closed - Valve Location Opens Closes Tricuspid Between the right During atrial systole During ventricular Valve atrium and right (right atrium contracts) systole (right ventricle ventricle contracts) Pulmonary Between the right During ventricular During ventricular Valve ventricle and systole (right ventricle diastole (right ventricle pulmonary trunk contracts) relaxes) Mitral Valve Between the left During atrial systole During ventricular (Bicuspid) atrium and left (left atrium contracts) systole (left ventricle ventricle contracts) Aortic Between the left During ventricular systole During ventricular Valve ventricle and aorta (left ventricle contracts) diastole (left ventricle relaxes)