UNIT 5 NOTES

BLOOD Blood is 55% plasma (liquid) which is composed of:

o 91% water – maintains blood volume and transports molecules o 7% proteins (ie. Clotting proteins, albumin, immunoglobulins o 2% salts, gases (O2, CO2), nutrients, wastes, hormones, vitamins, etc.

Blood is 45% formed elements (solids) which consists of:

1. Red Blood Cells (RBC) – aka: Erythrocytes

• No nuclei • Transport CO2 and O2 and H+ (acts like a buffer) • Biconcave discs • Live for ~ 120 days (4 months) • Contain hemoglobin molecules, carbonic anhydrase, and antigens • Made in the red bone marrow

2. White Blood Cells (WBC) – Leukocytes • Role: Fight infection – by producing antibodies OR through phagocytosis of pathogen • Formed in bone marrow & lymph tissue • WBC’s can squeeze out of blood vessels to attack invaders • WBCs Differ from RBCs: - they have nucleus, larger & fewer in number 5 types of leukocytes:

1) Basophiles a. release histamine when damaged which causes capillaries to dilate and

release fluid – fluid leaks into tissues = swelling 2) Neutrophils 3) Eosinophils 4) Monocytes

a. becomes macrophages (really large) at site of infection (inflammatory response) 5) Lymphocytes = T-cells →triggers immune response

= B-cells → release antibodies

3. Platelets • They are just fragments of cells (irregular shape) with no nuclei • Made in bone marrow • Aid in blood clotting • Recognize micro tears in blood vessels & bind together to form a blood clot

 

 

Clot formation process: • After injury, an enzyme is secreted to change a blood protein called fibrinogen (soluble) to fibrin (insoluble protein) • platelets + fibrinogen → “fibrin”

(in plasma) • Fibrin clumps at injury site & partially blocks leak • Fibrin threads trap blood cells to clot the injured site

BLOOD TYPES Antigen: an identification glycoprotein on a RBC • 2 kinds of antigens on human RBC's: A and B • Therefore, 4 possible blood types:

• Antigen A – type A blood • Antigen B – type B blood • Antigens A & B – type AB blood • No antigens – type O blood

Antibody: a protein designed to combat any foreign protein • Made by the WBC cells in the body • Will bind to foreign proteins with foreign antigens • This causes AGGLUTINATION = clumping • WBC’s will then destroy the agglutinated cells

Our blood has antibodies that are opposite to the antigens we have on our RBC’s • Why? – so we don’t attack our own blood!! Therefore blood transfusions are tricky: introducing foreign antigens can lead to…

DEATH!

Blood donor Blood Type A B AB O

A Yes Clumps Clumps Yes B Clumps Yes Clumps Yes

AB Yes Yes Yes Yes O Clumps Clumps Clumps Yes

 

BLOOD VESSELS The 5 Main Types

1. Arteries • Function – transport blood AWAY from the heart • Structure – thick, elastic walls • Location – usually deep, along bones • Notes - Walls can expand, arteries have very high Blood Pressure

o expansion is the “pulse” we feel

2. Arterioles • Function – Control blood flow to capillaries • Structure – smaller in diameter than arteries, thinner walls, have pre-capillary sphincters • Location – leading towards all capillaries • Notes – pre-capillary sphincter muscles to regulate blood pressure Problems with arteries/arterioles:

� Arteriosclerosis - hardening of the arteries – - reduces elasticity of artery walls

� Atherosclerosis = fatty deposits in arteries - reduces blood flow

→if in brain = stroke →if in heart = heart attack

• Aneurysm - Weakening of artery wall 3. Capillaries • Function – connect arteries to veins • Structure – very thin walls (1 cell thick) • Location – everywhere; within a few cells of each other, site of “capillary-tissue fluid exchange”

4. Venules • Function – drain blood from capillaries • Structure – thinner walls than veins • Location – often near the surface • Notes takes blood to veins

 

5. Veins • Function – transport blood TOWARDS the heart • Structure – inelastic walls, contain one-way valves • Location – often near to surface • Notes – blood pressure & velocity is much lower than in arteries.

Valves prevent blood from flowing backwards. Surrounded by skeletal muscle that “squeezes” blood along. Problems with Veins:

� varicose veins � valves become weak and allow the pooling and backflow of blood

� varicose veins of the rectum are called hemorrhoids CAPILLARY – TISSUE FLUID EXCHANGE Capillary-Fluid Exchange on Arteriole Side Arteriole Side (BP > OP)

• Blood pressure = 40 mmHg; Osmotic pressure = 25 mmHg • Net Blood pressure (15mmHg) forces water out of the blood into the extracellular fluid (ECF) • Water carries with it the O2 (HbO2) and nutrients (products of digestion) • Because there is more O2 and nutrients in interstitial fluid, it diffuses into body cells

• The large things (ie: RBC, WBC, platelets, blood proteins) stay in the capillary because they are too big to leave. • Because most of the water has left, the blood becomes very hyperosmotic (concentrated) • The venule side of the capillary is therefore under great osmotic pressure to draw water back into the blood.

Capillary-Fluid Exchange on Venule Side Venule Side (OP > BP)

• Osmotic pressure = 25 mmHg; Blood pressure = 10 mmHg • Blood very concentrated (has little water) • Net osmotic pressure (15mmHg) forces water back into the blood

• Water carries with it CO2 and metabolic wastes (urea) from ECF into the blood • These are carried to the kidneys and other excretory organs to be removed.

 

THE LYMPHATIC SYSTEM Functions of the lymphatic system:

1. Take up excessive tissue fluids from the ECF 2. Transport fatty acids and glycerol (from intestines to subclavian vein) 3. Fight infection (lymphocytes) 4. Trap and remove cellular debris

Structures of the Lymphatic System

1. Lymph Veins and Capillaries • Lymph capillaries drain and collect excess fluids from ECF which drains into a lymph vein • Lymph vein also contains valves to prevent backflow • Cleansed lymph travels through lymph vein to the subclavian vein

2. Lymph Nodes • Cleanse lymph fluid

3. Lacteals • Absorb / transport fatty acids & glycerol in the villi of the small intestine

4. Other Lymphoid Organs • Tonsils, appendix, spleen and thymus gland

THE HEART = a muscular organ that lies between the lungs – Myocardium: muscle tissue heart is made of – Pericardium: the double membrane “sac” that surrounds the heart.

• Pericardial fluid between membranes that lubricates to prevent friction

• The heart has 4 chambers: right atrium, right ventricle, left atrium, left ventricle

v The right side pumps deO2 blood to the lungs = PULMONARY v The left side pumps O2 blood to the body = SYSTEMIC Atria: the receiving chambers

o Right atrium: Receives deoxygenated blood from body via superior & inferior vena cava. o Left atrium: Receives oxygenated blood from the lungs via the pulmonary veins

 

 

 

Atrioventricular valves: 1. Separate the atria from the ventricles 2. They open when the atria contract 3. They prevent the blood from going backwards when the ventricles contract.

Chordae tendinae: Tendon-like pieces of tissue that keep the AV valves from inverting when the ventricles contract

Ventricles: the sending chambers • When the right atrium contracts, it pushes the blood through the AV valve and into the right ventricle. Right ventricle: When the RIGHT VENTRICLE contracts, BP forces the AV valve to close.

• The BP forces the PULMONARY semi-lunar VALVE open & the blood moves into the PULMONARY TRUNK

At the lungs: PULMONARY ARTERIES take deO2 blood to the lungs. CO2 is removed from the blood and is replaced with O2. PULMONARY VEINS take the O2 blood to the heart. What carries the oxygen? The protein HEMOGLOBIN binds the O2 tightly and carries it to the body cells as OXYHEMOGLOBIN! Septum: separates the 2 sides. The septum is a muscular wall that separates the right side of the heart from the left side. It keeps the deO2 blood from mixing with the O2 blood. Some people are born with a hole in their septum Left ventricle: When the left atrium contracts, it pushes the blood through the AV valve and into the left ventricle. When the LEFT VENTRICLE contracts, the AV VALVE is forced closed. Blood is forced through the AORTIC SEMI-LUNAR VALVE and enters the AORTA.

o The left ventricle has a THICKER muscle layer. WHY? Aorta The aorta is the biggest artery Coronary arteries and veins: The first branches of the aorta take the blood to the coronary arteries. Takes blood into the heart muscle itself. The coronary veins return the deO2 blood to the vena cava → right atrium. Vena Cava: There are two of these:

o Superior vena cava o Inferior vena cava

Path of blood through the heart Vena cava → right atrium → right AV valve → right ventricle → pulmonary semi-lunar valve → pulmonary trunk → pulmonary arteries / arterioles → pulmonary capillaries at lungs → pulmonary venules / veins → left atrium → left AV valve → left ventricle → aortic semi-lunar valve → aorta → body

Control of Heart Function: Electric Cardiac Cycle The SA node (sino-atrial):

l The SA NODE is found along the wall of the right atrium. It stimulates the simultaneous contraction of the atria.

l It also sends a nerve impulse along a nerve to the AV NODE l The SA node initiates the heartbeat and has been given the nickname of the “PACEMAKER”

The AV node (atrioventricular)

• In the right atrium close to the AV valve • When the AV node receives the impulse from the SA node, it fires to initiate the contraction of the

LARGE ventricles • The AV node sends its message through the Purkinje fibres (PF), which cause ventricles to contract.

Summary of Electric Cardiac Cycle

- medulla oblongata (in brain) sends electrical impulse to right atrium ↓

- SA node/pacemaker receives message & sends message through both atria to contract ↓

-impulse travels to AV node and down long nerve fibres = Purkinje fibres ↓

-ventricles contract (atria now relaxed) ↓

-entire heart rests Electrocardiogram: (EKG)

• There are two parts to the contraction of the heart • The heart beat is a double sound (‘lub-dub’). • An EKG (electrocardiogram) is a record of the electrical impulses measured across the surface of the

heart • The letters PQRST are the standard labels used to identify the parts of the EKG.

   EKG  

How is the brain involved? • The natural average resting heart rate is 72 beats per minute • The SA node is connected to the brain by the VAGUS NERVE (cranial nerve #10).

1. parasympathetic nerves regulate normal activities – May cause heartbeat to slow down during relaxation

2. sympathetic nerves respond to stress and increases blood flow to tissues therefore, speeds

heartbeat up • The regulation of the heartbeat is under the influence of the AUTONOMIC NERVOUS

SYSTEM (not under conscious control) • The part of the brain that governs the speed of the heart rate is called the MEDULLA

OBLONGATA • It will speed up or slow down the heart rate when needed. **Under normal circumstances,

the heart controls itself. BLOOD PRESSURE (BP)

• SYSTOLIC PRESSURE (systole): blood pressure when the ventricles are contracting. Blood is being forced through the arteries (approx. 120 mmHg)

• DIASTOLIC PRESSURE (diastole): blood pressure as ventricles are refilling / relaxing. This is between contractions, and the blood pressure is less (approximately 80 mmHg).

• Blood pressure is normally measured along the BRACHIAL ARTERY of the arm using a sphygmomanometer.

• A reading of 120/80 mmHg (systole/diastole) is normal. • When you are younger, your BP will be higher. Example: 13-15 yrs. will be 136-144 over 86-

92 BP changes throughout the body (in the different blood vessels) - BP is highest at beginning of aorta ~ 140 mmHg

120 mmHg - falls as goes through arteries - disappears in capillaries – close to zero (40-10 mmHg) - during inactivity blood doesn’t move and pools (low BP – below 10 mmHg) - BP in veins so low, veins need valves to help push blood back to heart

Hypertension: high blood pressure (ie: 150/100) Hypotension: low blood pressure (ie: 100/60)

What Factors Affect Blood Pressure? 1. Vessel diameter:

• Bigger (dilate) = lower BP • Smaller (constrict) = higher BP

2. Blood viscosity:

• Thick blood (little water) = higher BP • Thin (lots of water) = lower BP

3. Vessel elasticity: affected by plaques (fatty deposits)

• Elastic vessels = lower BP • Hardened vessels = high BP

4. Blood volume:

• Sweat a lot = less volume / water = lower BP • Eat lots of salt = more volume / water stays in the body = higher BP

5. Cardiac output

• Heart rate increases = higher BP • Heart rate decreases = lower BP

6. Age: as you get older, there is a loss of elasticity in the blood vessels.

• Young= very elastic = low BP • Old = not elastic = high BP

7. Stress: constricts blood vessels which means that there is increased pressure to move the blood.

• Stressed = constricted vessels = higher BP • Calm = normal vessels = lower BP

THE MAJOR BLOOD VESSELS

1. Aorta – Biggest artery. Carries O2 rich blood from heart (left ventricle) to body systems.

2. Coronary arteries/capillaries/veins – very first branch off the aortic arch. Blood vessels that “FEED” the heart muscle tissue

3. Carotid arteries – Branch off the aortic arch to take the blood to the head. Close to the surface and pulse is taken here.

4. Jugular Veins – Take blood out of the head region to the heart (via superior vena cava)

5. Subclavian arteries / capillaries / veins – Arteries branch off the aorta to feed chest wall and arms. Lymphatic vessels join the circulatory system at the subclavian veins before returning to the heart.

Mesenteric arteries – associated with the small intestine

6. Hepatic Portal Vein – Hepatic – liver; Portal = capillary bed on either end

This vein transports blood rich in nutrients directly from the intestines to the liver.

7. Hepatic veins – carries blood from the liver to the inferior vena cava

8. Renal arteries/capillaries/veins – renal arteries bring blood to the kidneys while renal veins take blood from the kidneys to the heart (via the inferior vena cava)

9. Iliac arteries / capillaries / veins – aorta branches into 2 iliac arteries which go down each leg. Iliac veins return blood to inferior vena cava.

10. Pulmonary arteries/capillaries/veins – deO2 blood collected from the body and is pumped into the pulmonary artery from the heart. Pulmonary artery takes deO2 blood to the lungs. Blood picks up O2 in the alveoli of the lungs. Pulmonary vein takes high O2 blood back to the heart.

11. Vena cava – largest vein. Carries deO2 blood from body to heart. a. Supeior vena cava – from head, chest & arms to the heart b. Inferior vena cava - from lower body to heart

 

CIRCULATION PATHWAYS 3 main functions of the circulatory system:

1. Transportation of: a. O2 and CO2 by blood cells b. Nutrients c. excretory wastes filtered from kidney’s

2. Regulation – carries hormones and other regulatory molecules 3. Protection

a. Clotting mechanism b. Leukocytes provide immunity

The Circulatory System is organized into two parts:

• Systemic Circulation: system of blood vessels that delivers oxygenated blood to body systems. • Pulmonary Circulation: system of blood vessels that delivers deoxygenated blood to the lungs to be replenished with oxygen

∼ The systemic arteries carry oxygenated blood. ∼ The pulmonary arteries carry deoxygenated blood.

1. Pulmonary Circuit: circulates blood through the lungs to the heart

Body tissues èright atrium èright ventricle èpulmonary trunk èpulmonary arteries èpulmonary arterioles èpulmonary capillaries (exchange) èpulmonary venules èpulmonary veins èleft atrium è left ventricle èaorta è body tissues….

2. Systemic Circuit: heart to the body tissues Example: the blood path to the kidney…. Superior and inferior vena cava è right atrium è right ventricle è lungs è left atrium è left ventricle è aorta è renal artery è renal arterioles è renal capillaries è renal venules è renal vein è inferior vena cava …….

• a blood cell will go through at least 2 capillary beds in the circulatory system: 1. the lung capillary bed for gas exchange 2. An organ capillary bed in the body

As part of the Systemic Circuit:

• The heart is supplied with its own coronary blood vessels to feed the heart tissue (myocardium) – the heart does not use the blood in its inner chambers

Problems with Coronary Circuit

∼ if a coronary artery becomes plugged (e.g. with cholesterol), and blood is not supplied to part of the heart, a heart attack occurs.

FETAL CIRCULATION

• The fetus does not use its lungs • Exchange of nutrients between mother & fetus takes place at the placenta

Placenta

• a large disk of tissue attached to the uterine wall where the mom’s and baby’s blood vessels are right next to each other

• allows for nutrient, waste and gas exchange to occur – the blood of mom and baby does NOT MIX!

►exchange occurs by diffusion There are 4 special circulatory features found only in the fetus: 1. Foramen Ovale / Oval Opening • opening between the Left and Right atria • allows the blood to bypass the lungs • It reroutes most of the blood from the right atrium into the left atrium.

2. Ductus Arteriosis / Arterial Duct • This is a small arterial connection, like a shunt. • Between the pulmonary artery and the aorta. • It further allows blood to bypass the lungs.

3. Umbilical Cord

The Umbilical Cord has 3 blood vessels: • The largest one, the umbilical vein, transports blood with oxygen and nutrients into the fetus. • The other two are umbilical arteries, which branch off of the iliac arteries in the fetus, and

take wastes and CO2 back into the mother via the placenta.

4. Ductus Venosus / Venus Duct • This blood vessel connects the umbilical vein to the vena cava. • The O2 blood from the umbilical vein mixes with deO2 blood in the vena cava. • The ductus venosus bypasses the liver and this blood is sent directly to the heart.

 

Changes that occur at birth: À The First Breath:

The lungs are filled with air instead of fluid and higher oxygen levels in the blood and alveoli results in an increase in pulmonary blood flow.

À Anatomical Changes:

The placenta is removed from circulation. The foramen ovale, ductus venosus, and ductus arteriosus close.

Ø The most common cardiac defects in newborns is that the oval opening fails to close

– causes pulmonary congestion • a “blue baby”

– Corrected by surgery À Path of blood through fetus

1. Begins with blood collecting in the right atrium 2. Blood can go into the left atrium through the oval opening plus into right ventricle through the AV

valve 3. Right ventricle to the pulmonary artery (most blood will go through the arterial duct into aorta) 4. Aorta to the tissue – umbilical arteries lead to the placenta (exchange of gases and nutrients) 5. Umbilical vein carries O2-rich blood- that enters the venous duct and bypasses the liver 6. Venous duct joins with the inferior vena cava; mixes with deoxygenated blood; then mixed blood

goes back to the heart

END OF CIRCULATORY SYSTEM NOTES