Circulatory System

Heart

Made mostly of cardiac muscle 4 chambers – 2 chambers on top (atria); 2

chambers on the bottom (ventricles) Right & left sides divided by the septum Right side has oxygen-poor blood Left side has oxygen-rich blood Valves between atria and ventricles and

between ventricles & vessels keep blood flowing in one direction

Heart

Two Separate Circulation Loops

Pulmonary Circulation: Oxygen–poor blood goes to the lungs to drop off CO2 and pick up O2 (returns to heart high in oxygen)

Systemic Circulation: Oxygen–rich blood goes around the body – gas exchange with individual cells (returns to heart low in oxygen)

Top Chambers (Atria)

Both top chambers receive blood

Top Right chamber receives oxygen-poor blood from the body

Top Left chamber receives oxygen-rich blood from the lungs

Bottom Chambers (Ventricles)

Each bottom chamber receives blood from the atrium above it, and pumps blood out of the heart

Bottom right chamber pumps blood into blood vessels that sends it to the lungs for gas exchange

Bottom left chamber pumps blood into the aorta that sends it to the body for gas exchange in tissues

Pathway of Blood through the Heart

Valves

There are 2 sets of valves between the top (atria) and bottom (ventricles) chambers

There are 2 sets of valves between the ventricles and blood vessels of the heart

The heartbeat sounds you hear are really the valves closing

Because there are 2 sets of valves closing, there are 2 sounds to the beat (“lub dub”)

Lub Dub

Blood Vessels

Arteries

Moves blood away from the heart

Walls are thick

Has smooth muscle on inside

Small in diameter, but elastic so it can expand

Veins

Moves blood towards the heart

Much thinner than arteries

Has smooth muscle on inside (< than arteries)

Larger in diameter

One–way valves to keep blood moving in one direction

Capillaries

Links arteries and veins in body cells

Thinnest blood vessels (1 cell thick)

Site of diffusion for gas exchange in lungs & body cells

Exchange in Body Cells… At the capillaries,

O2 and nutrients diffuse from bloodstream into body cells

CO2 and wastes diffuse from the body cells into the bloodstream

Exchange in Digestive System…

Water-soluble substances (including vitamin C) move from the intestines to the bloodstream (along with water) by osmosis

Small lipids also diffuse into blood

Some substances (including the sugar fructose) need transport proteins to get across the cell membrane

These substances travel down the concentration gradient – absorbed by facilitated diffusion

Exchange in Digestive System…