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Circulatory System

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by

Joy Penpenia

on 7 January 2013

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Transcript of Circulatory System

CIRCULATORY
SYSTEM Types of Blood Vessels: Heart Structure and Function: - The Blood Vessels
- The Heart
- The Vascular Pathways
- Blood A) ARTERIES
- large, carry blood away from the heart
- have thick elastic walls enabling them to stretch
- surrounded by smooth muscle that can control its size B) ARTERIOLES
- smaller than arteries
- made up mostly of smooth muscle C) CAPILLARIES
-microscopic blood vessels only 1 cell thick
- nutrient, gas, and waste exchange occur here and blood flow is controlled highly
- present all over the body
- often have sphincters (muscle rings) between arterioles and capillary beds to control flow of blood into the entire capillary bed D) VENULES
- drain blood from capillary beds
- begin flow towards the heart E) VEINS
- larger in terms of diameter
- have thinner walls than arteries
- have valves that allow blood to flow only in one direction towards the heart
- act as a blood reservoir ANATOMY OF A CAPILLARY BED: - when sphincter muscles are relaxed, the capillary bed is open and blood flows through
- when sphincter muscles are contracted, blood flows through a shunt that carries blood directly from an arteriole to a venule 3 ways to move blood to the heart: - valves that allow blood flow in one direction
- skeletal muscle, movement
- negative pressure from the heart (contracts/relaxes) INTRINSIC CONTROL OF THE HEART Both sides of the heart beat in synchronization. When both atrium contract, then both ventricles contract as well. NOTE: the right ventricle contracts a fraction of a second before the left ventricle :) SINOATRIAL NODE - located on the upper right atrium
- initiates heartbeat
- causes the atria to contract
- sends out a signal every 0.85 seconds ATRIOVENTRICULAR NODE - located on the lower right atrium
- when a signal from the SA node reaches here, this node causes the ventricles to contract NOTE: ventricles contract from the bottom, upwards :) (smaller than the branches of AV bundle) Both branches of AV bundle and purkinje fibers consist of specialized cardiac muscles causing the ventricles to contract. CHORDAE TENDINAE - strong fibrous strings that support valves
- attached to muscular projections on the ventricular walls
- prevents the valves from inverting when the heart contracts PASSAGE OF BLOOD
THROUGH THE HEART - superior and inferior vena cava, which carry O2-poor blood, then enters the right atrium

- the right atrium sends blood through an AV valve (tricuspid) to the right ventricle - the right ventricle sends blood through the pulmonary semilunar valve into the pulmonary trunk
- the pulmonary trunk divides into two pulmonary arteries, which go into the lungs - four pulmonary veins carrying O2-rich blood, then enters the left atrium
- the left atrium sends blood through an AV valve (bicuspid/mitral) to the left ventricle
- the left ventricle sends blood through the aortic semilunar valve into the aorta, to the body NOTE:
- O2-poor blood never mixes with O2-rich blood
- blood must go through the lungs in order to pass from the right side to the left side of the heart
- since the left ventricle has a harder job of pumping blood to the entire body, its walls are thicker than the right ventricle which only pumps blood a relatively short distance to the lungs EXTRINSIC CONTROL OF THE HEART * CHANGES TO THE HEARTBEAT - heartbeat is also under nervous control
- heartbeat center is in the brain (medulla oblongata) and it controls the pulse rate via the autonomic nervous system
- can speed up the heart via sympathetic nerves or slow it down via parasympathetic nerves (release neurotransmitters) - hormones from the adrenal medulla release epinephrine which stimulates heart rate
- many factors such as O2 and blood pressure can determine which system is activated. increased heart rate decreased heart rate SYSTOLE vs. DIASTOLE SYSTOLE - contraction of the ventricles DIASTOLE - relaxation of the ventricles
- chambers refilling
- the atria and ventricles passively fill
- AV valves allow blood to pass the aortic and pulmonary artery
-semilunar valves are closed because the blood in those vessels is at a higher pressure than the ventricles
- blood continues to fill atria and ventricles, stretching the compliant heart cells. -atria relaxation causes atrial pressure to be lower than ventricular pressure
-high ventricular pressure relative to the atria causes the AV valves to close, preventing backflow while the ventricles contract
-the ventricles continue to contract, ejecting blood through the semilunar valves out to the lungs and rest of the body. BLOOD PRESSURE HYPER vs. HYPOTENSION - hypertension is when the blood pressure is higher than expected (systolic number)
- this is usually an indication of cardiovascular disease ex: 150/100 Hypotension is when blood pressure is lower than expected. ex: 100/60 PRESSURE A number of factors
contribute to the reading: - sympathetic nerves and arterioles constricting increase blood pressure
- more Na+ in kidneys increase blood pressure
- ATHEROSCLEROSIS also increases blood pressure - hardening of the arteries
- accumulation of soft masses of fatty material
- interfere with blood flow and increase blood pressure
- can cause blood to form clots
- embolus occurs if the clot moves (causes a heart attack if it's a coronary artery or an artery in the brain) THE VASCULAR PATHWAYS PULMONARY vs. SYSTEMIC CIRCUIT BLOOD FLOW IN ARTERIES, CAPILLARIES & VEINS * blood pressure and velocity drop off in capillaries because capillaries have a greater cross-sectional area than arteries is the pressure of blood against the wall of a blood vessel - blood pressure decreases with distance from the left ventricle because there are more arterioles than arteries (increases the total cross-sectional area of blood vessels)
- decrease in blood pressure causes the blood velocity to gradually decrease as it flows toward the capillaries - blood flows even slower through the capillaries because there are more capillaries than arterioles
- this slow progress allows time for substances to be exchanged between the blood in the capillaries and the surrounding tissue - blood pressure is minimal in venules and veins
- instead of pressure, venous return depends upon skeletal muscle contraction, valves in veins, and respiratory movements ADULT/FETAL CIRCULATION main difference: the fetus receives its O2 blood from the placenta and does not use its lungs (oval opening) - an opening between the left and right atria
- covered by a flap that acts as a valve
- blood from the right atrium is shunted into the left atrium instead of the right ventricle
- reroutes blood away from pulmonary (lungs) to the systemic (body) system - a connection between the pulmonary artery and the aorta
- reroutes blood away from the lungs to the aorta - 2 arteries travel toward the placenta (away from the fetal heart) with love O2 and waste
- vein travels towards the fetus with O2-rich blood and nutrients - connection between the umbilical vein and the vena cava (via liver)
- umbilical vein carries O2 blood which mixes with unO2 blood in the vena cava (venous duct) (arterial duct) BLOOD contains: a) PLASMA
- 55%
- H2O and dissolved organic and inorganic substances b) CELLS (formed elements)
- 45%
- red blood cells, white blood cells, platelets PLASMA - H2O absorbed by the large intestines
- nutrients such as fats, glucose, amino acids and nucleotides
- salts, vitamins and proteins
- wastes (urea and ammonia)
- hormones from endocrine glands BLOOD CELL COMPONENTS A) RED BLOOD CELLS- erythrocytes - small biconcave disks with no nuclei (live 120 days)
- made in the red bone marrow
- pass through a number of developmental stages during which they loose a nucleus and gain hemoglobin
-transport O2 and CO2 B) WHITE BLOOD CELLS- leukocytes - larger and have a nucleus
- fewer in number in a healthy individual
- several kinds 2 kinds of white blood cells found in the body: 1) NEUTROPHILS - 55 to 70%
- granules in cytoplasm
- produced in bone marrow
- phagocytic
- many lobed nucleus 2) LYMPHOCYTES - 20 to 30%
- no granules in cytoplasm
- matured in lymph tissue, spleen, tonsils and thymus gland
- produce antibodies
- B & T cells
- mononuclear C) PLATELETS- cell bits - fragments of large, bone marrow cells
- involved in blood clotting
- produce 200,000,000,000 per day LYMPHATIC SYSTEM - transport fatty acids from intestines (lacteals)
- fight infection (lymphocytes)
- take up excessive tissue fluid ESSENTIAL FUNCTIONS: VESSELS AND ORGANS A) VESSELS
- lymph capillaries take up cell fluids
- lymph veins (have valves) B) LACTEALS
- blind ends found in the villi of intestines which absorb fats C) NODES
-small round structures
- produce lymphocytes that fight infection by producing antibodies which combine with, and deactivate foreign proteins
- filter and trap bacteria D) PARTS OF OTHER ORGANS
- tonsils, appendix, spleen, thymus gland - blood pressure at the arterial end of the capillary bed is higher than the osmotic pressure; water will be forced out through the walls, into the surrounding tissue; proteins and blood cells are too big, therefore they remain in the capillaries - O2, sugars and amino acids in the fresh blood diffuse into the tissue cells where they are used up; CO2 and wastes in the tissue cells diffuse out of the tissues and back into the blood - at the venule end, blood pressure is reduced and the osmotic pressure remains the same; H2O is pulled back into the blood vessels; remaining fluid is picked up and carried back to the circulatory system by the lymph system ANTIGENS, ANTIBODIES & BLOOD TYPING ANTIGEN ANTIBODY - a protein identification on the surface of a red blood cell - a protein made by the body designed to combat a foreign protein ANTIGEN + ANTIBODY ------> INACTIVE COMPLEX FOREIGN BODY AGGLUTINATION - 3 kinds of antigens that can be on a human red blood cell: A , B , Rh - therefore, there are 8 possibilities of blood types :) - within the plasma are antibodies of the antigens which are not present in the blood cell TRANSFUSIONS: - the donor's cells must be compatible with the recipient's plasma
- 'O' is the universal donor
- 'AB' is the universal recipient PULMONARY CIRCULATION - to the lungs
- involves the right side of the heart (right ventricle) which pumps deoxygenated blood into the pulmonary arteries to the lungs
- blood is then oxygenated in the capillaries of the alveoli
- it then returns tot he heart via pulmonary veins into the left atrium SYSTEMIC CIRCULATION - is to the body
- blood is pumped out of the left ventricle into the aorta where it heads off via a number of blood vessels to the rest of the body
- collects to return to the heart in two major veins
- superior vena cava drains the head and upper body, inferior vena cava drains the lower body (both enter the right atrium) NOTE: all vessels leaving the heart carry oxygenated blood, and all vessels returning to the heart carry unoxygenated blood (opposite to pulmonary system NOTE: pulmonary arteries from right ventricle to the lungs carry unoxygenated blood, pulmonary veins from the lungs to the left atrium carry oxygenated blood and the lungs act as the capillary system for O2/CO2 exchange
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