Mammalian Circulation

The Heart The heart is a fist-sized, muscular organ that pumps blood through the body. Every day, the heart pumps about 7,600 liters of blood, beating about 100,000 times.

Blood vessels are organized into 3 primary cycles. 1. Cardiac Circulation: the route taken by the blood within the heart. 2. Pulmonary Circulation: pathway of the blood from the heart to the lungs and back. 3. Systemic Circulation: route from the heart to the rest of the body. It includes all blood vessels other than those associated with the lungs.

A circulatory system has three main elements: 1. Transport vessels: conduct fluid from one area to another. 2. Transport medium: specialized fluid tissue that carries substances around the body. 3. Pumping mechanism.

Mammalian Circulatory System includes 3 main types of blood vessels: 1. artery 2. vein 3. capillary NOTE : The classification of blood vessels also includes: arteriole (a small artery)and venule (a small vein).

Arteries Carry blood away from the heart. Most carry oxygenated blood (pulmonary artery is the exception). They contain elastic walls that expand as blood passes through and snaps back. They have thicker layers of muscle than veins (because blood flows through at high pressure).

Veins carry blood toward the heart. Most veins carry deoxygenated blood. They lack elasticity but have a greater (blood) capacity than the arteries. The blood flows through a vein at low pressure. They have valves every few centimeters that allow the blood to flow in one direction. Skeletal muscles also aid in the blood movement. The pulmonary vein returns oxygenated blood from the lungs back to the heart to be pumped into systemic circulation.

Capillaries are a single layer of epithelial cells which allows for easy diffusion. It forms a wall that regulates the movements of fluids and other materials into and out of the blood stream. Blood is pumped to the body capillaries via the aorta, (the largest artery in the body).

Veins vs. Arteries

The Mammalian Heart : It is made up of cardiac muscle (that contracts repeatedly without fatigue). It is surrounded by a protective layer called the pericardium.

Mamallian Heart

Heart of a mammal is divided into 4 chambers Right and left Atria Right and left Ventricles Atria - collecting chambers. - receive blood from the lungs and body. - pump blood to the ventricles.

Ventricles - thick muscular wall. - pumping chambers that push blood out through blood vessels and capillary beds.

Valves Bicuspid Valve (mitral) - located between left atrium and left ventricle. - has two parts or cusps.   Tricuspid Valve - located between the right atrium and right ventricle. - contains 3 cusps.

Valves Aortic Semilunar Valve - Located between the left ventricle and the aorta Pulmonary Semilunar Valve - allows blood to travel from right ventricle to the rest of the body.

Other Parts Septum - wall that separates right and left ventricles. Pulmonary Vein - returns oxygenated blood from the lungs back to the heart to be pumped into systemic circulation.   Pulmonary Artery - carries deoxygenated blood from the heart to the lungs.

Flow of blood Inferior/superior vena cava  Right atrium  Tricuspid valve (atrioventricular valve)  Right ventricle  pulmonary Semilunar valve  Pulmonary artery  Lungs  Pulmonary vein  Left atrium  Bicuspid valve (atrioventricular valve)  Left venticle  aortic semilunar valve  Aorta

Blood: A Transport Medium

Blood -a collection of cells specialized to perform a particular task within an organism. -considered to be a tissue.

Erythrocytes -        red blood cells. -        make up 44% of total blood volume. -        adult male has 5.5 million rbc/mL of blood. (female: 4.5 million). -        specialized for oxygen transport -        disk-shaped and contains no nucleus. -        contains respiratory pigment hemoglobin. -        rarely lives more than 3-4 months.

Hemoglobin -        iron-containing molecule that binds with oxygen. -        allows oxygen to be transported in the blood.

- also known as leucocytes. White Blood Cells -        also known as leucocytes. -        make up approximately 1% of blood volume but increases when fighting infection. - contain a nucleus and appear colorless. - two most important wbc are: 1. Macrophages - phagocytic cells that pass through the walls of capillaries to engulf and digest pathogens. 2. Lymphocytes - non-phagocytic cells that play a role in body’s immune response that enables body to recognize and fend off specific pathogens.

Platelets not cells. -fragments of cells that were created when larger cells in bone marrow break apart. fragments break down quickly in blood (last only a week to 10 days). play an important role in blood clotting.

Blood Plasma - fluid portion of the blood. - medium in which blood is suspended. -        contain plasma proteins. 1.  Albumin - keeps water from entering or leaving the blood and entering the surrounding cells by osmosis. 2.  Fibrinogen - clotting of blood. 3.  Globulins - transport of proteins and other substances from one part of the body to another.