BLOOD

Chapter 10

NHS Anatomy/Physiology

Human Red Blood Cells, Platelets and T-lymphocyte (erythocytes = red; platelets = yellow;T-lymphocyte = light green) (SEM x 9,900).

INTRODUCTION - Formed – hemopioesis

Functions - transport, Protection, Regulation, osmotic pressure

Composition - Plasma + formed element - 5.6 L

Blood Composition

• Blood Plasma 1. Definition-blood minus its cells 2. Composition-water containing many dissolved

substances (for example glucose, salts, plasma proteins and hormones)

3. Amount of blood-varies with size and sex: 4 to 6 L about average about 7% to 9% of body weight

4. Slightly alkaline 7.25-7.35 pH

B. Formed elements 1. Kinds a. RBCs (erythrocytes) b. WBCs (leukocytes) (1) Granular leukocytes- neutrophils, eosinophils,

and basophils. (2) Nongranular leukocytes-lympphocytes and

monocytes c. Platelets or thrombocytes

2. Numbers a. RBCs-4½ to 5 million per mm3 of blood b. WBCs-5000 to 10,000 per mm3 of blood c. Platelets-300,000 per mm3 of blood 3. Formation- red bone marrow (myeloid tissue) - hemoposoieses

forms all blood cells except some lymphocytes and monocytes, which are formed by lymphatic tissue in the lymph nodes, thymus, and spleen.

C RBCs

1. Structure-Disk-shape, without nuclei

2. Functions-Transport oxygen and carbon dioxide

3. Anemia-inability of blood to carry adequate oxygen to tissues;

caused, for example, by:

a. Inadequate RBC numbers

b. Deficiency of hemoglobin

c. Pernicious anemia-Deficiency of vitamin B12

4. Hematocrit -Medical test in which a centrifuge is used to separate whole blood into formed elements and liquid fraction

a. Buffy coat is WBC and platelet fraction

b. Normal RBC level is about 45%

c. Polycythemia-Abnormally high RBC count

WBCs

1. General Function- Defense

2. Neutrophils and monocytes carry out phagocytosis

3. Lymphocytes produce antibodies (B-lymphocytes) or directly attack foreign cells (T-lymphocytes)

4. Eosinophils protect against irritants that cause allergies

5. Basophils produce heparin, which inhibits clotting

6. Clinical conditions related to blood:

a. Leukopenia-abnormally low WBC count

b. Leukocytosis-abnormally high WBC count

c. Leukemia-cancer; elevated WBC count; cells do not function properly

Platelets and blood clotting 1. Platelets play an essential role in blood clotting 2. Blot clot formation a. Clotting factors released at the injury site

produce prothrombin activator b. Prothrombin activator and calcium convert

prothrombin to thrombin c. Thrombin triggers formation of fibrin, which

traps RBC to for a clot

BLOOD TYPESA. ABO system

1. Type A blood-type A antigens in RBCs; anti-B type antibodies in plasma

2. Type B blood-type B antigens in RBCs; anti-A type antibodies in plasma

3. Type AB blood- type type A and type B antigens in RBCs; no anti A or anti B antibodies in plasma

4. Type O blood-no type A or type B antigens in RBCs; both anti-A and ant-B antibodies in plasma

1. Rh-positive blood-Rh factor antigen present in RBCs2. Rh-positive blood- Rh factor antigen present in RBCs; no anti-Rh antibodies present naturally in plasma; anti-Rh antibodies, however, appear in the plasma of Rh-negative persons if Rh-positive RBCs have been introduced into their bodies

3. Erythroblastosis fetalis-may occur when Rh-negative mother carries a second Rh-positive fetus; caused by mother’s Rh antibodies reacting with baby’s Rh-positive cells

RH FACTOR

Chapter 11

The Circulatory SystemLack

System

Open Circulatory System - Sluggish

Closed Circulatory

System

Anterior view showing major arteries (white) and veins (black) 1 Internal jugular vein 2 Common carotid artery 3 Subclavian vein and artery 4 Brachial artery 5 Cephalic vein 6 Basilic vein 7 Inferior vena cava 8 Radial artery 9 Ulnar artery 10 Common iliac artery and vein 11 Femoral artery 12 Great saphenous vein 13 Heart 14 Aorta 15 Femoral vein

Introduction

• Cardiovascular system- vital for supplying oxygen and nutrients to tissues and removing wastes from them.

Structure of the Heart • Cone-shaped, muscular pump,

found in thoracic cavity

• Size and Location of the Heart – The average adult heart is 14

cm long and 9 cm wide– The heart lies in the

mediastinum under the sternum; its apex extends to the fifth intercostal space.

C. Coverings of the Heart • The pericardium encloses the heart.

– Fibrous pericardium surrounds a more delicate visceral pericardium (epicardium) that surrounds the heart.

– At the base of the heart, the visceral pericardium folds back to become the parietal pericardium that lines the fibrous pericardium.

– Between the parietal and visceral pericardia is the pericardial cavity filled with serous fluid.

D. Wall of the Heart • The outermost layer the

epicardium - connective tissue and epithelium - houses blood and lymph capillaries along with coronary arteries.

• The middle layer - myocardium is the thickest layer of the heart wall.

• The inner layer - endocardium is smooth connective tissue and epithelium, and is continuous with the endothelium of major vessels joining the heart.

Heart Chambers and Valves

• The heart has four internal chambers: two atria on top and two ventricles below

• Atria receive blood returning to the heart

• The thick-muscled ventricles pump blood to the body.

• The right ventricle - thin wall - pumps blood to lungs

• aortic + pulmonary valves - prevent return to ventricles

• Tricuspid between right atria and right ventricle

• bicuspid (mitral) between left atria and left ventricle

Skeleton of the Heart • Rings of dense connective tissue lie at the plane in

which the A-V orifices and aortic and pulmonary valves lie; these rings make up the skeleton of the heart.

• These tough rings prevent dilating of tissue in this area.

Path of Blood through the Heart • Blood low in oxygen returns to the right atrium• The right atrium contracts, forcing blood into the right ventricle• The right ventricle contracts forcing blood through the pulmonary valve into

the pulmonary trunk and arteries.• The pulmonary arteries carry blood to the lungs where it can rid itself of

excess carbon dioxide and pick up a new supply of oxygen.• Freshly oxygenated blood is returned to the left atrium of the heart through the

pulmonary veins.• The left atrium contracts, forcing blood into the left ventricle.

• The left ventricle contracts forcing open the aortic valve as blood enters the aorta for distribution to the body. - SYSTEMATIC CIRCULATION

Blood Supply to the Heart • The first branches off of the aorta carry

freshly oxygenated blood

• Branches of the coronary arteries feed many capillaries of the myocardium.

• The heart muscle requires a continuous supply of freshly oxygenated blood, so smaller branches of arteries often have anastomoses as alternate pathways for blood, should one pathway become blocked.

• Cardiac veins drain blood from the heart muscle and carry it to the coronary sinus, which empties into the right atrium.

Heart Actions • The cardiac cycle consists of the atria

beating in unison followed by the contraction of both ventricles

• pressure within the heart chambers rises and falls with the contraction and relaxation of atria and ventricles.

• When the atria fill, pressure in the atria is greater than that of the ventricles, which forces the A-V valves open.

• As the ventricles contract, papillary muscles contract, pulling on chordae tendinae and preventing the backflow of blood through the A-V valves - Mitral, tricuspid

Heart Sounds • Heart sounds are due to vibrations in heart tissues

as blood rapidly changes velocity within the heart.– Heart sounds can be described as a "lub-dup" sound.

• The first sound (lub) occurs as ventricles contract and A-V valves are closing.

• The second sound (dup) occurs as ventricles relax and aortic and pulmonary valves are closing.

Cardiac Conduction System

• Specialized cardiac muscle conducts impulses throughout the myocardium and comprises the cardiac conduction system

• Path= S-A Node, AV- Node A-V bundle - Perkinje fibers– A self-exciting mass of specialized cardiac muscle

called the sinoatrial node (S-A node or pacemaker), located on the posterior right atrium, generates the impulses for the heartbeat.

Electrocardiogram

• An electrocardiogram is a recording of the electrical changes that occur during a cardiac cycle.– The first wave, the P wave, corresponds to the

depolarization of the atria.

– The QRS complex corresponds to the depolarization of ventricles and hides the repolarization of atria.

– The T waves ends the ECG pattern and corresponds to ventricular repolarization.

Regulation of the Cardiac Cycle • The amount of blood pumped at any one time must adjust to the

current needs of the body

• The S-A node is innervated by branches of the sympathetic and parasympathetic divisions, so the CNS controls heart rate.

• Sympathetic impulses speed up and parasympathetic impulses slow down heart rate.

• medulla oblongata maintains a balance between the sympathetic/parasympathetic

• Impulses from cerebrum or hypothalamus may also influence heart rate, as do body temperature and the concentrations of certain ions.

Blood Vessels • The blood vessels (arteries, arterioles,

capillaries, venules, and veins) form a closed tube that carries blood away from the heart, to the cells, and back again.

• 3 tunics - intima - media - adventita• Arteries are strong, elastic vessels adapted for

carrying high-pressure blood.• Veins - thin walled, valves, towards the heart• Capillaries are the smallest vessels, consisting

only of a layer of endothelium through which substances are exchanged

• Capillary permeability varies from one tissue to the next

Capillaries

• Areas with a great deal of metabolic activity (leg muscles, for example) have higher densities of capillaries.– If blood is needed elsewhere in the body, the capillary

beds in less important areas are shut down.

Venules and Veins

• Venules leading from capillaries merge to form veins that return blood to the heart.

• Veins have the same three layers as arteries have and have a flap-like valve inside to prevent backflow of blood.

• Veins are thinner and less muscular than arteries; they do not carry high-pressure blood.

• Veins also function as blood reservoirs.

Blood Pressure • Blood pressure is the force of blood against the inner walls of blood

vessels

• Arterial Blood Pressure

• Arterial blood pressure rises and falls following a pattern established by the cardiac cycle.

• During ventricular contraction, arterial pressure is at its highest (systolic pressure). 120 mm Hg When ventricles are relaxing, arterial pressure is at its lowest (diastolic pressure). 80 mm Hg - Pulse

Paths of Circulation

• Blood vessels can be divided into a pulmonary circuit and systematic circuit

• Pulmonary Circuit – The pulmonary circuit is made up of vessels that convey blood

from the right ventricle to the pulmonary arteries to the lungs, alveolar capillaries, and pulmonary veins leading from the lungs to the left atrium.

• Systemic Circuit – The systemic circuit includes the aorta and its branches

leading to all body tissues as well as the system of veins returning blood to the right atrium.

Hepatic Circulation• Hepatic portal circulation -stomach , spleen,

gallbaldder, pancreas - venous return by way of liver

Fetal Circulation• Fetal placenta

circulation via 2 umbilical arteries and 1 umbilical vein

• ductus venosus - liver by pass

• ductus arteriosus - lung by pass

• foramen ovale - lung by pass

Arterial System • The aorta is the body's largest artery.

• Principal Branches of the Aorta

• The branches of the ascending aorta are the right and left coronary arteries that lead to heart muscle.

• Principal branches of the aortic arch include the brachiocephalic, left common carotid, and left subclavian arteries.

• The descending aorta (thoracic aorta) gives rise to femoral arteries which supply lower extremities

Venous System • Veins return blood to the heart after

the exchange of substances has occurred in the tissues.

• Larger veins parallel the courses of arteries and are named accordingly; smaller veins take irregular pathways and are unnamed.

• Veins from the head and upper torso drain into the superior vena cava.

• Veins from the lower body drain into the inferior vena cava.

• The vena cavae merge to join the right atrium.

Clinical considerations

• Coronary thrombosis

• angina pectoris

• pulse

• cardiac output - volume per minute

• stroke volume - amount of blood pumped per contraction