NOTES: CH 42, part 1

(Circulation in Animals)

● Diffusion alone is NOT adequate for

transporting chemicals over distances in

animals

● The circulatory system ensures that no

substance must diffuse very far to enter

or leave a cell

The circulatory system…

provides oxygen and nutrients to tissues

and removes wastes.

STRUCTURE OF THE HEART

Size:

● about 14 cm long and 9

cm wide

Location:

● 2/3 left of midline

● below 2nd rib and rests

on diaphragm

STRUCTURE OF THE HEART

Heart Covering:

● fibrous, outer pericardium:

parietal pericardium

● serous, inner pericardium:

visceral pericardium

● space between the layers =

pericardial cavity (cushions

and lubricates heart)

4 Heart Chambers: (heart is divided into right and left sides)

● RIGHT:

RIGHT ATRIUM receives blood from the superior and inferior venae cavae and coronary sinus

pumps blood into the RIGHT VENTRICLE

right ventricle pumps blood out of the heart into the PULMONARY ARTERIES (take blood to the lungs)

● LEFT:

LEFT ATRIUM

receives blood from the

pulmonary veins (from

the lungs)

pumps blood into the

LEFT VENTRICLE

left ventricle pumps

blood out of the heart

into the AORTA (takes

blood to all of the body)

Heart Valves: designed to prevent backflow of blood!

ATRIOVENTRICULAR VALVES:

-TRICUSPID VALVE: separates R atrium from R ventricle

-BICUSPID VALVE(a.k.a. MITRAL VALVE): separates L atrium from L ventricle

● Structure of AV valves:

-CHORDAE TENDINAE: strong fibrous

structures that attach to the flaps of the

valves

-PAPILLARY MUSCLES:

muscles embedded

in the endocardium;

attach to the

chordae tendinae

SEMILUNAR VALVES:

-PULMONARY VALVE:

separates R ventricle

from pulmonary arteries

-AORTIC VALVE:

separates L ventricle

from aorta

Path of Blood Through the Heart:

● blood low in oxygen and high in CO2

enters the RIGHT SIDE through the venae

cavae and is then pumped into

pulmonary circulation (to the lungs)

Path of Blood Through the Heart:

● after blood is oxygenated

in the lungs, it returns to

the LEFT SIDE through

the pulmonary veins and

is then pumped into

systemic circulation via

the aorta (to the body)

Heart Blood Supply:

● the CORONARY ARTERIES supply blood

to the myocardium

● blood returns to the R atrium through the

cardiac veins and coronary sinus

**500,000 Americans die per year of

coronary artery disease

**3.5 million Americans have coronary

problems

Cardiac Cycle

● ATRIAL SYSTOLE: atria

contract while the ventricles relax

(VENTRICULAR DIASTOLE)

● VENTRICULAR SYSTOLE:

ventricles contract while the atria

relax (ATRIAL DIASTOLE)

● all chambers relax for a brief

period…; then the cycle repeats!

Diastole Systole

Initiation of Cardiac Cycle:

● electrical impulses originate in the SA

node: stimulate the atria to contract

● impulses pass slowly to the AV node,

then to the Purkinje fibers: stimulate the

ventricles to contract

ELECTROCARDIOGRAM (ECG):

● records the electrical changes in the

myocardium during a cardiac cycle

● the pattern has several characteristic

waves:

1) P wave: atrial depolarization

2) QRS complex: ventricular

depolarization

3) T wave: ventricular repolarization

Regulation of Cardiac Cycle:

● heartbeat is affected by:

-physical exercise

-body temperature

-concentration of ions (calcium, potassium)

Blood Vessels and

Blood Pressure

Blood vessels form

a closed circuit of

tubes that carry

blood from the

heart to body cells

and back again.

ARTERIES and ARTERIOLES

● Arteries are adapted to carry blood under

HIGH PRESSURE away from the heart.

● Arteries eventually

branch into smaller

structures called

ARTERIOLES

CAPILLARIES

● smallest diameter blood vessel

● connect arterioles to venules

● capillary wall = a single layer of cells; forms a semipermeable membrane

RBCs in a

capillary!

CAPILLARIES● tissues that use more

energy/oxygen have the most

capillaries (i.e. muscle tissue,

nerve tissue)

● tissues that use less

energy/oxygen have the

fewest capillaries (i.e.

epidermis, cartilage)

Exchanges in Capillaries:

● blood in capillaries drops off

their nutrients and oxygen in

exchange for metabolic

wastes (CO2, etc.)

● large molecules (e.g. plasma

proteins) remain in the blood

● most materials move across

the capillary wall by

DIFFUSION

VEINS and VENULES

● VENULES continue from capillaries and merge with VEINS

● veins carry blood TOWARD THE HEART

● venous walls are similar in structure to artery walls, but thinner and contain less muscle tissue

ARTERIES

-carry blood

away

from heart

-largest artery =

AORTA

ARTERIOLES

CAPILLARIES

-walls are only

1 cell thick

VENULES

VEINS

-carry blood to the

heart

-thinner walls

-are less muscular

than arteries

BLOOD PRESSURE:

Blood pressure is the force blood exerts

against the sides of blood vessels.

BLOOD PRESSURE:

● SYSTOLIC PRESSURE: pressure produced in the arteries when the ventricles contract; highest pressure

● DIASTOLIC PRESSURE: pressure in the arteries when the ventricles are relaxed

Venous blood pressure is much lower than arterial

blood pressure…how does blood flow through

veins (in some cases, against gravity?)

skeletal muscle contractionsqueezes blood from one segment to the next

breathing movements change pressure in thoracic and abdominal cavities pulling/pushing blood upward toward the heart

VALVES prevent blood from flowing backward into a previous segment

2 MAJOR PATHS OF CIRCULATION:

● PULMONARY CIRCUIT: vessels that

carry blood from the heart to the lungs

and back

R ventricle pulmonary trunk R and L

pulmonary arteries arterioles and

capillaries in the R and L lungs venules

veins pulmonary veins L atrium

2 MAJOR PATHS OF CIRCULATION:

● SYSTEMIC CIRCUIT: carries blood from the heart to all other body parts and back again; includes coronary circulation

L atrium L ventricle aorta various arteries, arterioles, capillaries in body tissues venules veins superior and inferior venae cavae R atrium

BLOOD AND BLOOD CELLS

Blood can be separated into:

• Formed elements:

-mostly red blood cells (RBCs)

-include white blood cells (WBCs) and platelets

• Liquid portions = PLASMA

-transports water, gases, nutrients, hormones,

electrolytes, and cellular wastes

Red Blood Cells (RBCs)

• contain HEMOGLOBIN,

which combines with oxygen

• hemoglobin synthesis requires IRON

White Blood Cells (WBCs)

• function in defense against disease

• also called: LEUKOCYTES

• WBCs include:

neutrophils monocytes

eosinophils lymphocytes

basophils

White Blood Cells (WBCs)

• normal WBC count is 5,000 – 10,000 cells

per mm3 of blood

this number may vary in response to

infection, emotional disturbances, loss of

body fluids, leukemia

Platelets

• fragments of larger cells

• help close breaks in blood vessels / clot

the blood

PLASMA

Plasma transports gases and nutrients,

helps regulate fluid and electrolyte

balance, and helps maintain a stable pH.

PLASMA

Gases in plasma:

-oxygen

-carbon dioxide

-nitrogen

Plasma nutrients:

-simple sugars

-amino acids

-lipids

ABO Blood Group:

• blood is grouped according to the presence or

absence of antigens A and B.

Type A = A antigens; plasma has anti-B antibodies

Type B = B antigens; plasma has anti-A antibodies

Type AB = A and B antigens; no antibodies

Type O = neither antigen; both anti-A and B antibodies

ABO Blood Group:

• mixing RBCs that contain an antigen with plasma that contains the corresponding antibody results in a negative reaction (AGGLUTINATION)

*the anti-A and anti-B

antibodies are too large

to cross the placenta,

so mother and child can

safely have different ABO blood groups

The Blood Typing

Game!

Rh Blood Group:

• Rh-positive blood: RBCs possess the Rh antigens

• Rh-negative blood: RBCs do not possess the Rh antigens, but DO possess anti-Rh antibodies

RESULT: mixing Rh-positive RBCs with plasma that has the anti-Rh antibodies can result in agglutination

Rh Blood Group:

*the anti-Rh antibodies are small enough to

cross the placenta…

So, the anti-Rh antibodies in a mother’s

blood could react with the RBCs of an Rh-

positive fetus

The “Rh Issue”…

Mom = Rh-; Baby #1 = Rh+

A note

about blood

pressure…

How do we measure B.P.?

● To measure arterial blood pressure, we

use a device known as a

sphygmomanometer …

…GUESS WHAT…????

SPHYGMOMANOMETER!

***word #5 on my list!!!...the list is complete!

1) Okazaki fragments

2) plasmodesmata

3) cholecystokinin

4) acetylcholinesterase

5) sphygmomanometer

6) rubisco

7) chaperonins

8) Islets of Langerhans

9) Batesian mimicry

10) nodes of Ranvier

SPHYGMOMANOMETER:

● This device consists of an inflatable cuff

connected by rubber hoses to a hand

pump and to a pressure gauge.

● The cuff is wrapped around the upper arm

and inflated to a pressure greater than the

expected systolic pressure, thus closing

down the brachial artery in the arm.

SPHYGMOMANOMETER:

● The examiner

places the bell of a

stethoscope in the

inside of the elbow

below the biceps

muscle to pick up

the sounds of the

blood in the artery as

the pressure in the cuff is allowed to fall.

(This is done gradually by opening a screw valve

next to the hand pump.)

SPHYGMOMANOMETER:

● At first there is no sound; then, a sharp, tapping

sound of blood spurting through the partially-

opened artery at systolic pressure;

● and ultimately, no sound as even the low-

pressure blood (@ diastolic pressure) can get

through the completely open artery.

**(The various sounds heard with the stethoscope

are known as the sounds of Korotkoff.)

BLOOD PRESSURE:

● Blood pressure is recorded as: systolic pressure (mm Hg) / diastolic pressure (mm Hg).

● A normal blood pressure measurement for a given individual depends on the person’s age, sex, heredity, emotional state, body weight, etc.

● For young men and women at age 17-18, the normal BP’s will range from 100-120 mm Hg systolic pressure, and from 60-80 mm Hg diastolic pressure.

“Is my blood pressure too high?”

● One “high” BP reading may not indicate a health problem;

● BP needs to be measured over several days at different times of the day by a health care professional before a true measure is achieved.

● Blood pressure measurements that arechronically elevated may indicate poor cardiovascular health.

● This condition, called hypertension, is a major contributor to heart disease and stroke.