Quaestio: What structures transport substances throughout the human body?

Nunc Agenda:What are 3 parts of a circulatory system?What are they called in the human body?

Function of the Circulatory System

• To transport oxygen, nutrients, and other dissolved substances throughout the body

• Remove wastes from cells• Maintain body temperature by distributing

heat

Vertebrate circulatory system overview

• Heart pumps blood– Atrium – collects blood from veins– Ventricle – pumps blood out to the body

• Blood Vessels– Arteries – carry blood away from the heart– Capillaries – tiny vessels where exchange of

materials between blood and body cells occurs– Veins – carry blood toward the heart

Other vertebrate hearts• Fish – 2 chamber heart– 1 atrium, 1 ventricle

• Amphibians – 3 chamber heart– 2 atria, 1 ventricle

• Birds / mammals – 4 chamber– 2 atria , 2 ventricles– Prevents oxygenated and deoxygenated blood from

mixing, allows for more efficiency and ability to be warm-blooded

The Developing Heart of a Zebrafish Embryo

http://bioimaging.caltech.edu/index_content.html

Note: In Crocodilians, heart is actually completely separated. They can prevent blood from flowing through the pulmonary circuit while underwater by using a muscular valve.

Overview of Vertebrate Circulatory Systems

Interesting…

• Average adult body contains about 5 L of blood• On average , your blood circulates from your

heart, throughout your body and back about every 60 seconds.

• Everyday your heart beats about 100,000 times• First heartbeat in human embryo occurs about

4-5 weeks after conception• The leading cause of death in the US is heart

disease

The heart is a muscular double-pump• Pulmonary circulation – right side of the heart

pumps deoxygenated blood to the lungs– Heart lungs– Pulmo = “lung” (latin)– -ary = “belonging to or connected with”

• Systemic circulation – left side of the heart pumps oxygen rich blood to the rest of the body– Heart brain and body

Blue=Deoxygenated blood.Red = oxygenated blood

Lungs replenish the blood with oxygen.

How it works: RBCs pick up O2 through diffusion across the capillary membrane.

Pericardium – a tough membrane that covers the heart and protects it

The Heart• The heart consists of four chambers:– 1. Left Atrium– 2. Left Ventricle– 3. Right Atrium– 4. Right Ventricle

• Atria: Upper, thin-walled chambers.• Ventricles: Lower, thick-walled chambers.• Septum: A wall that separates the left and right

sides of the heart.• Valves: flaps of tissue that prevent blood from

flowing backwards

The heart

• Composed almost entirely of cardiac muscle– Cells are connected together in an electrical

network that stimulates contraction– When one cell is stimulated, all of the fibers

contract at the same time– Can work continuously without getting tired

Cardiac Muscle Cells

Human Heart Beat

• 2 contractions1. Atria contract “lub”• Begins at the SA node (sinoatrial) a.k.a. “the pacemaker”• Electrical impulse spreads causing both atria to contract

2. Ventricles contract “dub”• Impulse is picked up by the AV node (atrioventricular)• Split-second delay then both ventricles contract, pumping

blood out of the heart– (allows both atria to contract and ventricle to fill with blood)

Circulation Pathways (1)• Steps:– 1. Deoxygenated blood enters the right atrium of the

heart from the body tissues.• This blood reaches the heart through the superior and inferior

vena cava veins.

– 2. Deoxygenated blood is pumped from the right atrium to the right ventricle through a valve.

– 3. Deoxygenated blood is pumped out of the heart to the lungs by the right ventricle.• This blood is pumped out through the pulmonary artery.

– 4. The lungs replenish the blood with oxygen. It is now oxygenated blood.

Circulation Pathways (2)• Steps:– 5. Oxygenated blood enters the left atrium of the heart

from the lungs.• This blood reaches the heart through the pulmonary veins.

– 6. Oxygenated blood is pumped from the left atrium to the left ventricle through a valve.

– 7. Oxygenated blood is pumped out of the heart to the body tissues by the left ventricle.• This blood is pumped out through the aorta.

– 8. The body tissues use the oxygen carried by the red blood cells. The blood then becomes deoxygenated and must be returned to the heart where the cycle repeats.

Simplified Sequence• Blood flows from

Right Atrium Right Ventricle Lungs Left Atrium Left Ventricle Rest of Body Right Atrium again.

Pulmonary Circuit:Right Ventricle Lungs Left Atrium

Systemic Circuit:Left Ventricle Body Right Atrium

Questions• The left ventricle is the largest chamber of the

heart. How is its size related to its function?• If the valves in the right ventricle do not close

properly, where in the body might circulation be affected the most?

• Why is it important to have two separate pathways for circulation?

• Describe some of the adaptations of the mammalian heart that allow it to be efficient and coordinated.