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.

• • located between the right atrium and right ventricle.

• -

Tricuspid Valve

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

• to returns oxygenated blood from the lungs back the heart circulation.

to be pumped into systemic •

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 valve  Pulmonary vein  venticle   pulmonary Semilunar Pulmonary artery  Lungs Left atrium valve (atrioventricular valve)   Left aortic semilunar valve Bicuspid   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.

•

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.