human biology (biol 104) talk six: the heart and blood vessels chapter 7

Human Biology (BIOL 104)

Talk Six:

The Heart and Blood Vessels

Chapter 7

• Three basic components:• Heart - serves as pump

that establishes the pressure gradient needed for blood to flow to tissues

• Blood - transport medium within which materials being transported are dissolved or suspended

• Blood vessels - passageways through which blood is distributed from heart to all parts of body and back to heart

Homeostasis Review

Homeostasis Review

• The cardiovascular system delivers:– Oxygen, nutrients,

hormones, and other substances to body cells

• It carries away wastes and substances cell produce

• Flowing blood also carries excess heat to the body surface

The Closed Circulatory System

•Humans have a closed circulatory system, typical of all vertebrates, in which blood is confined to vessels and is distinct from the interstitial fluid.

–The heart pumps blood into large vessels that branch into smaller ones leading into the organs.

–Materials are exchanged by diffusion between the blood and the interstitial fluid bathing the cells.

From the wikimedia free licensed media file repository

The Heart• The largest part of the

heart is usually slightly offset to the left (though occasionally it may be offset to the right).

• The heart is usually felt to be on the left side because the left heart is stronger, since it pumps to all body parts. – The left lung in turn is

smaller than the right lung because it has to accommodate the heart. 

From the wikimedia free licensed media file repository

The Heart• The heart is supplied by the

coronary circulation and is enclosed in the pericardial sac.

• Comprised of two parts: the fibrous pericardium, made of dense fibrous connective tissue, and the serous pericardium.

• Between the outer parietal layer and the visceral serous layer is the pericardial cavity which contains the pericardial fluid which protects and lubricates the heart

From the wikimedia free licensed media file repository

Heart has four chambers

• Two upper atria, – the receiving chambers

• Two lower ventricles– the discharging

chambers.

• The right atrium – receives deoxygenated

blood from the body

• The left atrium– receives oxygenated blood

from the lungs. From the wikimedia free licensed

media file repository

Heart has four chambers

• When these contract the blood is pushed into the ventricles, which pump to propel the blood to the lungs and the rest of the body.

• The right atrium and the right ventricle together are sometimes referred to as the right heart and this sometimes includes the pulmonary trunk.

From the wikimedia free licensed media file repository

Heart has four chambers

• Similarly, the left atrium and the left ventricle together are sometimes referred to as the left heart.

• The atrioventricular septum separates the left heart from the right heart, giving two functional units.

From the wikimedia free licensed media file repository

Heart Skeleton

•Consists of plate of fibrous connective tissue between atria and ventricles

•Fibrous rings around valves to support

•Serves as electrical insulation between atria and ventricles

•Provides site for muscle attachment

The Heart Valves• One-way valves prevent

backflow during contraction

• (AV) Valves- between atria and ventricles

• Blood pressure closes valve cusps during ventricular contraction

• Papillary muscles– prevent valves from swinging

into atria

• Regurgitation -Failure of valves– Causes backflow of blood

into atria

Figure 20–8

How cardiac muscle contracts

• Nodes and fiber bundles:

• (1) Sinoatrial node—Pacemaker– Starts heartbeat (every

0.85 seconds)– Atria begins to contract

• (2) Artioventricular node– Signal To Ventricles– Signal passed on by fibers:

• (3) Artioventricular Bundle– Signal to Bottom of

Ventricles

• (4) Purkinje Fibers—– Signal to Ventricular

Muscle

How cardiac muscle contracts• Transmission of a cardiac

action potential through the heart's conduction system

From the wikimedia free licensed media file repository

• Heart cells must beat in unison. Intercalated Disks allow calcium to regulate united beating

Mazz’s quick ‘n’ easy guide to the working of a nerve firing

• Remember the ion channels of plasma membranes?

• Resting Potential– Same electrical ion charge

inside and outside of cell– Said to be polarized

• Action Potential• Depolarization occurs by the

movement of K+ and Na+ ions– 3 Na+ ions are pumped out

and 2 K+ ions are pumped in– This makes and change in

the voltage of the cell of muscle tissue, causing contraction

• Repolarization– Reverse ion flow – back to

resting potential From Wikimedia Commons, a freely licensed media file repository

How cardiac muscle contracts• Measuring the heart's

conduction system

• P wave – Atria depolarization

• QRS complex– Ventricle depolarization– Atria repolarization

• T wave – Ventricle repolarization

From the wikimedia free licensed media file repository

From the wikimedia free licensed media file repository

Copyright ©The McGraw-Hill Companies; used with permission

• Superior vena cava and inferior vena cava carries O2-poor blood to the Right Atrium

• Right atrium sends blood via tricuspid valve to R. Ventricle

• Right Ventricle sends blood to pulmonary trunk – – Divides up into two pulmonary

arteries - go to lungs

• Four pulmonary veins carry O2-rich blood to Left Atrium

• Left Atrium sends blood via Mitral valve to L. Ventricle

• Left Ventricle sends blood via semilunar (Aortic) valve to the Aorta and then to body Copyright ©The McGraw-Hill

Companies; used with permission

Flow of blood to and from the heart

Copyright ©The McGraw-Hill Companies; used with permission

Cardiac Cycle• Heart is two pumps that

work together, right and left half

• Repetitive contraction (systole) and relaxation (diastole) of heart chambers

• Blood moves through the circulatory system from areas of higher to lower pressure.– Contraction of heart

produces the pressure

Heart Sounds• First heart sound or

“lubb”– Atrioventricular valves and

surrounding fluid vibrations as valves close at beginning of ventricular systole

• Second heart sound or “dupp”– Results from closure of aortic

and pulmonary semilunar valves at beginning of ventricular diastole, lasts longer

• Third heart sound (occasional)– Caused by turbulent blood

flow into ventricles and detected near end of first one-third of diastole

The Heart• The heart pumps 7,000

liters of blood through the body each day

• The heart contracts 2.5 billion times in an average lifetime

• The heart and all blood vessels make up the cardiovascular system

• The blood vessels make up two circuits– Pulmonary circuit– Systemic circuit

Copyright ©The McGraw-Hill Companies; used with permission

The double pump – Pulmonary and systemic circulation

The Cardiovascular System

The Blood, a quick look

A. Plasma• Liquid portion of the blood.

• Contains: • clotting factors, • Hormones• Antibodies• dissolved gases• Nutrients• waste

Copyright ©The McGraw-Hill Companies; used with permission

The Cardiovascular System

The Blood, a quick look

B. Erythrocytes - Red Blood Cells

• Carry hemoglobin and oxygen.

• Do not have a nucleus and live only about 120 days.

• Can not repair themselves.

Copyright ©The McGraw-Hill Companies; used with permission

The Cardiovascular System

The Blood, a quick look

C. Leukocytes – White Blood cells

• Fight infection and are formed in the bone marrow

• Five types – • neutrophil, • lymphocytes • eosinophils • basophils• monocytes.

Copyright ©The McGraw-Hill Companies; used with permission

The Cardiovascular System

The Blood, a quick look

•D. Thrombocytes – Platelets.

•These are cell fragment that are formed in the bone marrow from magakaryocytes.

•Clot Blood by sticking together – via protein fibers called fibrin.

Copyright ©The McGraw-Hill Companies; used with permission

The Cardiovascular System

Blood Vessels -A network of tubes

–Arteriesarterioles move away from the heart•Elastic Fibers•Circular Smooth Muscle

–Capillaries – where gas exchange takes place.•One cell thick•Serves the Respiratory System

–VeinsVenules moves towards the heart•Skeletal Muscles contract to force blood back from legs•One way values•When they break - varicose veins form

Copyright ©The McGraw-Hill Companies; used with permission

Arteries / Arterioles• Carry Blood AWAY from

Heart - Strong and Stretchy

• 3 layers:– Endothelium with

Elastic Basement fibers

– Thick Smooth Muscle & Elastic fibers• Contract to

regulate blood flow & pressure

– Fibrous Outer Layer

From Wikimedia Commons, a freely licensed media file repository

Arteries / Arterioles

• Arteries branch to form Arterioles:– muscle layer in

Arterioles controls our blood flow and blood pressure!

– More Arterioles contracted at one time – HIGHER your blood pressure

From Wikimedia Commons, a freely licensed media file repository

Veins• Have the same three

layers of arteries• BUT LESS SMOOTH

MUSCLE & CONNECTIVE TISSUE

• Thin walled – so expand to a greater extent – Stretchy

• Veins have much lower blood pressure and thinner walls than arteries

• To return blood to the heart, veins have special adaptations– Large-diameter lumens,

which offer little resistance to flow

– Valves (resembling semilunar heart valves), which prevent backflow of blood

From Wikimedia Commons, a freely licensed media file repository

Veins• Act as a reservoir for

blood– At any time 70% of

blood in veins

• Valves allow blood to return to the heart– This occurs against

the force of gravity

• If blood is being lost nervous action causes veins to constrict, providing more blood for the body

From Wikimedia Commons, a freely licensed media file repository

Special features of veins

• Valves– Prevent backflow – Most abundant in legs

(where blood has to travel against gravity)

• Muscular contraction– Aids the return of blood

to heart in conjunction with valves

From Wikimedia Commons, a freely licensed media file repository

35

• Exercise helps circulation!

• because muscles contract and squeeze blood back to the heart.

Special features of veins

Capillaries• 1 cell thick

• Nutrients and oxygen diffuse out of blood through caps into our tissues

• Waste products and CO2 diffuse from our tissues back into the blood

• Are organized into Beds

• Beds open or close--control by nervous system– stomach beds open for

digestion.

Vessel summary

From Wikimedia Commons, a freely licensed media file repository

Capillary Beds• The capillaries are the

smallest unit of the circulatory system,

• Connect the arterioles and the smaller veins (venules) .

• Arterioles bring blood from the heart which is rich with oxygen and nutrients, while

• Venules carry blood which has become deoxygenated back to the heart.

From Wikimedia Commons, a freely licensed media file repository

Capillary Beds• A capillary bed is a

concentration of capillaries which supply blood to a specific organ or area of the body.

• The density of the capillaries in a given bed can vary, depending on the requirements of the area it supports.

• Precapillary sphincters - regulate the flow of blood to tissues From Wikimedia Commons, a freely

licensed media file repository

Capillary Beds• These areas are an

important part of the circulatory system

• Marks the point where the circulation reaches its terminus

• Circulation then loops back around to allow blood to pass through the heart

• Blood is then reoxygenated so that it can return to circulation.

From Wikimedia Commons, a freely licensed media file repository

Capillary Beds• At the capillary bed, fresh

blood drops off water, O2, and nutrients, collecting waste materials such as CO2 from the cells so that they can be removed from the body.

• Although the circulatory system may seem like a closed network of tubes, the capillaries are: – actually permeable,

allowing substances to pass into and out of the capillary across a thin membrane.

From Wikimedia Commons, a freely licensed media file repository

Capillary Beds

• In organs with heavy nutrient and oxygen requirements, such as the liver, the capillary bed may be quite extensive

• Point to remember:

• At any given time capillary beds usually holds up to around 25% of the total blood supply of a human

From Wikimedia Commons, a freely licensed media file repository

Capillary Beds - Summary

• Forms a maize of capillaries which lies between Artery and vein system.

• When sphincter is relaxed (OPEN)– Blood flows through capillaries

• Allows capillary exchange to occur

• When sphincter is contracted (SHUT)– Blood flows through a shunt that carries it

directly from an Arteriole to a Venule.– Known as an arteriovenous shunt

Capillary Exchange• Remember Osmosis?

• Arterial end of capillary– Blood pressure HIGHER than osmotic pressure

• Water leaves the bloodstream

Capillary Exchange• Remember Osmosis?

• Midsection• Small molecules follow concentration gradient• O2 & nutrients leave. Wastes and CO2 enter

Capillary Exchange• Remember Osmosis?

• Venous end of capillary• Osmotic pressure HIGHER than blood pressure• Water enters the bloodstream About 85% water

return form arterial end.

Disorders of the Circulatory System

• Anemia - lack of iron in the blood, low RBC count

• Leukemia - white blood cells proliferate wildly, causing anemia

• Hemophilia - bleeder’s disease, due to lack of fibrinogen in thrombocytes

• Heart Murmur - abnormal heart beat, caused by valve problems

• Heart attack - blood vessels around the heart become blocked with plaque, also called myocardial infarction

Cardiovascular Disease• Also called heart disease is a class of diseases that

involve the heart, the blood vessels (arteries, capillaries, and veins) or both.

• Any disease that affects the cardiovascular system, principally cardiac disease, vascular diseases of the brain and kidney, and peripheral arterial disease.

• Leading cause of deaths worldwide, though, since the 1970s, cardiovascular mortality rates have declined in many high-income countries

• At the same time, cardiovascular deaths and disease have increased at a fast rate in low- and middle-income countries

Cardiovascular Disease• Atherosclerosis:

– An artery wall thickens as a result of the invasion and the accumulation of white blood cells

• This accumulation of the WBCs is termed "fatty streaks" early on because of appearance being similar to that of marbled steak.

• These accumulations contain

both living, active WBCs (producing inflammation) and remnants of dead cells, including cholesterol and triglycerides.

From Wikimedia Commons, a freely licensed media file repository

Effects of Aging on the Heart

• Gradual changes in heart function, minor under resting condition, more significant during exercise

• Hypertrophy of left ventricle

• Maximum heart rate decreases

• Increased tendency for valves to function abnormally and arrhythmias to occur

• Increased oxygen consumption required to pump same amount of blood

The End!