Blood vessels and circulation

• Systemic circulation carries oxygenated blood away from the heart to the body and returns deoxygenated blood back to the heart.
• Pulmonary circulation carries deoxygenated blood from the heart to the lungs and oxygenated blood is returned to the heart.
• Arteries transport blood away from the heart.
• Veins transport blood towards the heart.
• Capillaries is a meshwork of fine vessels between arteries and veins where tissue perfusion occurs.
• Structural layers of arteries and veins

  A) Endothelium

  B) Tunica Media

  C) External Elastic Lamina

  D) Tunica Externa

  E) Vaso Vasorum

  F) Venous Valves

  G) Internal Elastic Lamina

  H) Tunica Intima

  
• Valves in the veins are bicuspid flaps of elastic tissue.
• Venous blood pressure is low, so the valves function to keep blood moving in one direction preventing backflow.
• Conducting Elastic Arteries are large arteries with a lot of elastic tissue which they expand as they receive blood during systole (contraction) and recoil diastole (relaxation).
• Distributing Muscular Arteries are medium arteries with more smooth muscle than elastic tissue and distributes blood to specific organs.
• Resistance Arteries are small arteries with a lot of smooth muscle and minimal elastic tissue, "Arterioles" are the smallest and major point of control to how much blood the tissues receives.
• Veins are capacitance vessels that is able to expand to accommodate increased volume.
• Postcapillary Venules are the smallest veins that receive blood from the capillaries, is porous (holes) and able to exchange fluid with tissues.
• Medium veins have smooth muscle and maybe elastic tissues; contains venous valves.
• Venous Sinuses are thin walls with large lumens with no smooth muscle; receives blood from a collection of veins.
• Large Veins have smooth muscle and a very large lumen.
• Capillaries are organized into a capillary bed that functions to exchange substances between the blood and tissues.
• Metarterioles link arterioles and capillaries. They have smooth muscle cells at points along the vessel, each forming a precapillary sphincter.
• Capillaries are regulated by constriction (systole) or dilation (diastole) of arterioles.
• Most capillaries are not fully perfused because there's not enough blood to fill them all.
• Continuous Capillaries is where endothelium forms a continuous tube where small solutes can pass but proteins, cells and large molecules do not.
• Fenestrated Capillaries is where Endothelial cells with numerous pores which allows passage of small molecules but protein and large ones do not. (Important in organs engaged in rapid filtration and absorption such as kidneys and endocrine glands)
• Sinusoids are irregular blood-filled spaces (liver, bone marrow, and spleen) where endothelial cells are separated by wide gaps, allowing proteins and cell to enter the blood.
• Systolic Pressure is the peak blood pressure attained duringventricular contraction.
• Diastolic Pressure is the minimum blood pressure that occurs duringventricle relaxation.
• Peripheral Resistance is the resistance of the arteries to bloodflow.
• When arteries constrict their resistance increases; If arteries dilate, their resistance decreases.
• As viscosity increases, blood flow slows.
• Vasoconstriction narrows a vessel to raise blood pressure while Vasodilation widens a vessel to lower blood pressure.
• Pressure and flow decrease with distance.
• Compliance is the tendency of the arteries and veins to stretch.
• Compliance of a vein is about 10 to 20 times greater than an artery because veins accommodate large changes in blood volume with only small chance in pressure.
• Autoregulation is where the tissue regulates its own blood supply; stimulate vasodilation to increase blood flow to remove waste and metabolic products.
• Neural is the innervation by central and autonomic nervous system; vasomotor center in the medulla oblangata which exerts sympathetic control to stimulate vessels to constrict.
• Hormonal is when vessels are affected by hormones such as angiotensin, aldosterone, atrial natriuretic peptide, ADH, Epinephrine and Norepinephrine.
• Arterial Atherosclerosis is where plaque builds up inside arteries that slowly blocks and interfere with blood flow; Most common cause of heart attack, strokes, and vascular disease.