Anatomy Unit 4

Plasma

Liquid, extracellular matrix component of blood, primarily water, containing dissolved proteins, electrolytes, hormones, and waste products

Erythrocytes

Biconcave, anucleated red blood cells, responsible for transporting oxygen (O₂) from the lungs to the tissues and carbon dioxide (CO₂) from the tissues to the lungs, primarily through the iron-containing protein hemoglobin

Leukocytes

Various types of nucleated white blood cells (neutrophils, lymphocytes, monocytes, eosinophils, basophils) that function as key components of the innate and adaptive immune system to defend the body against pathogens and foreign materials

Thrombocytes

Small, anucleated cell fragments (platelets) derived from megakaryocytes that are essential for hemostasis, primarily by forming a platelet plug and initiating the clotting cascade

Antigens

Molecules (often proteins or polysaccharides) found on the surface of cells (e.g., erythrocytes, pathogens) that are capable of eliciting a specific immune response, leading to the production of antibodies

Antibodies

Y-shaped plasma proteins (immunoglobulins) produced by B lymphocytes that specifically recognize and bind to a particular antigen to neutralize or mark it for destruction by other immune cells

Hemoglobin

A quaternary protein molecule within erythrocytes, composed of four globin chains and four heme groups (each containing an iron atom), which reversibly binds and transports the majority of oxygen in the blood

Hemostasis

A complex, multi-step physiological process that halts bleeding (hemorrhage) following vascular injury, involving vascular spasm, platelet plug formation, and blood coagulation (clotting)

Arteries

Muscular, thick-walled blood vessels that transport oxygenated blood (except the pulmonary artery) away from the heart to the capillaries; they are typically high-pressure vessels due to the pumping action of the ventricles

Veins

Thin-walled blood vessels that return deoxygenated blood (except the pulmonary vein) from the capillaries back toward the heart; they are lower pressure vessels and contain one-way valves, particularly in the limbs, to prevent the backflow of blood

Capillaries

Microscopic, thin-walled (single layer of endothelium) blood vessels that form extensive networks within tissues, serving as the primary site for the exchange of gases (O₂, CO₂), nutrients, waste products, and hormones between the blood and the interstitial fluid

Systole

The phase of the cardiac cycle when the ventricles contract, ejecting blood into the pulmonary artery and the aorta, resulting in the highest blood pressure reading

Diastole

The phase of the cardiac cycle when the ventricles relax and fill with blood returning from the atria, resulting in the lowest blood pressure reading

Pericardium

A double-walled sac that encloses the heart and the roots of the great vessels

Parietal pericardium

The tough, fibrous outer layer and the inner serous layer that lines the fibrous sac

Visceral pericardium (Epicardium)

The serous layer that adheres directly to the outer surface of the heart muscle

Myocardium

The thick, muscular middle layer of the heart wall, composed of specialized cardiac muscle cells responsible for the powerful pumping contractions of the heart

Endocardium

The smooth, thin, inner lining of the heart chambers (atria and ventricles) and valves, composed of simple squamous epithelium (endothelium) overlying connective tissue, continuous with the endothelium of the blood vessels

Atria

The two superior, thin-walled receiving chambers of the heart (right atrium and left atrium) that collect blood returning from the systemic and pulmonary circuits

Ventricles

The two inferior, thick-walled pumping chambers of the heart (right ventricle and left ventricle) that propel blood into the pulmonary and systemic circuits, respectively

Septum

A wall or partition that divides the heart into right and left sides; the interatrial septum separates the atria, and the interventricular septum separates the ventricles

Valves

Specialized structures within the heart that ensure unidirectional blood flow by preventing backflow between chambers or into the great vessels

Tricuspid Valve

The right atrioventricular (AV) valve located between the right atrium (RA) and the right ventricle (RV), typically having three cusps

Mitral (Bicuspid) Valve

The left atrioventricular (AV) valve located between the left atrium (LA) and the left ventricle (LV), typically having two cusps

Pulmonary Valve

A semilunar valve located between the right ventricle (RV) and the pulmonary artery, preventing backflow into the RV during diastole

Aortic Valve

A semilunar valve located between the left ventricle (LV) and the aorta, preventing backflow into the LV during diastole

Chordae Tendineae / Papillary Muscles

Fibrous cords (chordae tendineae) that anchor the cusps of the AV valves to muscular projections (papillary muscles) on the ventricular walls, preventing the valve leaflets from prolapsing or flipping back into the atria during ventricular systole

Electrical Conduction

The intrinsic system of specialized cardiac muscle cells that generates and transmits electrical impulses throughout the heart, coordinating the rhythmic cycle of contraction and relaxation

SA Node (Sinoatrial Node)

Located in the right atrial wall, this is the primary pacemaker of the heart, initiating the depolarization wave

AV Node (Atrioventricular Node)

Located in the interatrial septum, this node receives the impulse from the atria and introduces a critical delay before transmitting the impulse to the ventricles, allowing for complete ventricular filling

Bundle of His (AV Bundle)

The specialized tract of conducting fibers that transmits the impulse from the AV node down into the interventricular septum

Purkinje Fibers

Extensive network of conducting fibers that rapidly distribute the depolarization wave throughout the ventricular myocardium, triggering synchronous ventricular contraction

Vessel Layers (Tunics)

The three concentric layers that make up the walls of most blood vessels

Tunica Intima

The innermost layer, consisting of a smooth endothelial lining and a basement membrane, which minimizes friction for efficient blood flow

Tunica Media

The middle layer, composed primarily of smooth muscle cells and elastic fibers, responsible for vasoconstriction and vasodilation to control blood pressure and flow distribution

Tunica Externa (Adventitia)

The outermost layer, composed of collagen fibers, which provides structural support, protection, and anchors the vessel to surrounding structures

Plasma Proteins

The most abundant solutes in plasma, contributing to osmotic pressure, transport, and immunity

Albumin

The most abundant plasma protein, synthesized by the liver, essential for maintaining plasma osmotic pressure (preventing edema) and transporting various substances like hormones & drugs

Globulins

A diverse group of plasma proteins, including immunoglobulins (antibodies) for immunity and transport globulins that shuttle various lipids, metal ions, and fat-soluble vitamins

Fibrinogen

A soluble plasma protein that is the inactive precursor to fibrin; it is essential for the final stage of the coagulation cascade, forming the insoluble meshwork of a blood clot

Vascular Resistance

The opposition to blood flow through the vessels, caused primarily by the friction between the flowing blood and the vessel walls; it is affected by blood viscosity, total vessel length, and, most significantly, vessel diameter

Blood Pressure

The force exerted by the blood against the wall of a blood vessel; it is directly proportional to Cardiac Output (the volume of blood pumped by the heart per minute) multiplied by Total Peripheral Resistance (the overall resistance of the systemic blood vessels)

Pleurae

Serous membranes that surround the lungs and line the thoracic cavity, composed of the visceral pleura (adhering to the lung surface) and the parietal pleura (lining the cavity), separated by the fluid-filled pleural cavity

Gas Exchange

The process of diffusion where oxygen (O₂) moves from the alveoli in the lungs into the pulmonary capillaries, and carbon dioxide (CO₂) moves from the pulmonary capillaries into the alveoli, driven by differences in partial pressures

Lung Volumes

Standardized measurements used to assess the amount of air that can be inhaled, exhaled, or remains within the lungs

Tidal Volume (TV)

The volume of air inhaled/exhaled during a single, normal breath

Inspiratory Reserve Volume (IRV)

The maximum volume of air that can be forcibly inhaled after a normal tidal inspiration

Expiratory Reserve Volume (ERV)

The maximum volume of air that can be forcibly exhaled after a normal tidal expiration

Residual Volume (RV)

The volume of air that remains in the lungs and airways even after a maximal forced exhalation; this air cannot be exhaled

Vital Capacity (VC)

The maximum volume of air that can be exchanged in one breath; the sum of TV + IRV + ERV

Total Lung Capacity (TLC)

The total volume of air the lungs can hold; the sum of VC + RV

Ductus Arteriosus

In the fetal circulation, a shunt that connects the pulmonary artery to the aorta, bypassing the non-functional fetal lungs

Ductus Venosus

In the fetal circulation, a shunt that bypasses the liver by connecting the umbilical vein directly to the inferior vena cava

Foramen Ovale

In the fetal circulation, an opening in the interatrial septum that allows blood to flow directly from the right atrium to the left atrium, bypassing the non-functional fetal lungs

Pulmonary Artery

The single large artery originating from the right ventricle, which carries deoxygenated blood to the lungs; it is unique as an artery carrying deoxygenated blood

Pulmonary Vein

The blood vessels (typically four) that return oxygenated blood from the lungs to the left atrium; they are unique as veins carrying oxygenated blood

Umbilical Artery

In fetal circulation, the arteries that carry deoxygenated blood and metabolic waste products from the fetus to the placenta

Umbilical Vein

In fetal circulation, the vein that carries oxygenated, nutrient-rich blood from the placenta to the fetus

Alveoli

Microscopic, thin-walled, sac-like structures at the terminal ends of the respiratory bronchioles, which are the primary sites for pulmonary gas exchange

Surfactant

A lipoprotein mixture produced by Type II alveolar cells that reduces the surface tension within the alveoli, preventing them from collapsing and making inspiration easier