Circulatory System Part 1

What are the major functions of blood? (8)

* Oxygen transport
* Carbon dioxide transport
* Food transport
* Waste transport
* Blood clotting
* Defense against disease
* Hormone transport
* Heat distribution

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What is the name of the cell that is responsible for transporting oxygen?

Erythrocytes (red blood cell)

Which type of blood cell is the most numerous?

Erythrocytes (red blood cell)

Why are red blood cells (erythrocytes) red?

They have hemoglobin (red pigment) that makes up 95% of the cell’s dry matter

What is hemoglobin?

A molecule composed of four heme groups attached to a central globin (protein)

Why is hemoglobin important? (2)

* It has iron, which bonds temporarily with oxygen molecules
* Can carry 60 times as much oxygen as can be dissolved in the plasma, providing sufficient oxygen for the body

How many oxygen molecules can one hemoglobin molecule carry at once?

Four

What is oxyhemoglobin?

Hemoglobin that is combined with oxygen to form a bright red compound

Where is oxyhemoglobin present?

In areas of high oxygen concentration (ex: lungs)

What is deoxyhemoglobin?

Hemoglobin that has its oxygen separated from it, forming a dark purplish compound

Where is deoxyhemoglobin found?

In areas of low oxygen concentration (ex: most body tissues)

What is the danger of carbon monoxide? (4)

* Hemoglobin has a great affinity (tends to bond) for carbon monoxide
* Carbon monoxide can take up spots on the hemoglobin that are meant to be for oxygen
* If CO is bound to hemoglobin, oxygen cannot be transported and tissues do not receive enough oxygen
* Can lead to death

Describe the properties of carbon monoxide:

* Colourless
* Odourless

How can we avoid carbon monoxide exposure?

* Do not run the engine of a car in a closed garage
* Do not stay inside a car if the exhaust is faulty

What is carbon dioxide?

A waste product of cellular respiration

How can carbon dioxide be carried in the blood? (3)

* A small percentage is carried by the plasma in a dissolved state
* A small percentage is carried by hemoglobin
* Most are carried as bicarbonate ions and hydrogen ions

What is carbonic acid?

The product of carbon dioxide reacting with water in the blood plasma

What is the significance of carbonic acid?

* Carbonic acid can break down into bicarbonate and hydrogen ions
* When the ions reach the lungs, a reverse reaction occurs and the carbonic acid’s ions react to form carbon dioxide and water
* Carbon dioxide is released and exhaled from the body

Digested foods are carried in the blood plasma as end products. What are these end products?

* Simple sugars (carbohydrates, nucleic acids)
* Amino acids (proteins)
* Fatty acids and glycerol (lipids)
* Vitamins
* Minerals

How are digested foods transported through the blood?

They are carried in the blood plasma as end products

How are wastes transported through the body?

Cellular wastes such as nitrogen wastes of ammonia OR urea are dissolved in the plasma and carried in the blood

Why is blood clotting important?

It prevents excessive blood loss

Describe the clotting process: (9)

* Blood vessel ruptures or is cut
* The body recognizes that a vessel has been damaged because of its surface, and platelets come into contact with the damaged area
* Platelets break open and release thromboplastinogen, then adhere to the broken vessel
* The area becomes sticky and collects other platelets, allowing a plug to form
* Thromboplastinogen is activated by an enzyme and clotting factors, turns into thromboplastin
* Thromboplastin turns prothrombin into thrombin
* Thrombin turns soluble fibrinogen into insoluble fibrin
* Fibrin forms a network across the opening of the vessel
* Clot is formed and slows blood flow, eventually stops it if the damage is not too bad

What is the function of plateles/thrombocytes?

To function in clotting of blood and repair of damaged blood vessels

Which other plasma proteins are necessary for clotting?

* Prothrombin
* Fibrinogen

When are prothrombin and fibrinogen present in the blood?

At all times, and are only activated when damaged (inactive the rest of the time)

What is thromboplastin?

An enzyme that, in the presence of calcium ions, catalyzes the conversion of prothrombin to thrombin

What is thrombin?

An enzyme that catalyzes the conversion of fibrinogen into fibrin

Why don’t clots form inside undamaged vessels?

Because heparin circulates in the blood

What is heparin?

An anticoagulant that normally prevents clotting in intact vessels

What are the types of defenses against disease? (3)

* Physical (outer covering of the body, prevents entry of organisms into the body)
* Cellular defenses
* Chemical defenses

Which cells are involved in cellular defense?

Leucocytes (neutrophils and lymphocytes)

What are leucocytes responsible for?

The destruction of bacteria

What happens when bacteria break through the outer defenses? (3)

* Capillaries dilate
* Leucocytes are attracted to the area and begin engulfing diseased bacteria
* Leucocytes are killed while destroying the bacteria, then accumulate in pockets with other dead tissues and plasma to form pus

Which cells are involved in chemical defense?

Lymphocytes and monocytes

What do lymphocytes and monocytes do in chemical defense?

They produce antibodies that make an organism immune to infection

What are antigens?

Foreign proteins that can enter the body and trigger the production of antibodies

What are antibodies?

Proteins that destroy antigens

What is the significance of the thymus gland?

It produces lymphocytes, which are important in antibody production especially during infancy and early childhood

What is natural immunity?

Immunity that results when antibodies are already in the blood without stimulation from an antigen

What is acquired immunity?

Immunity that results after the body has been exposed to the disease

How can someone develop acquired immunity?

* Exposure to the disease
* Vaccination

What is active immunity?

Immunity that results from an exposure stimulates antibody production

What is passive immunity?

Immunity that results from an inoculation of antibodies to help the body fight the antigen

What are the differences between active and passive immunity? (2)

* Active immunity involves own production of antibodies and lasts a lifetime
* Passive immunity involves being given antibodies and lasts only as long as the antibodies survive

How do hormones act on a cell? (3)

* Hormone travels in blood and reaches the target cell
* Hormones attaches to cell surface on a specific site
* The attachment of the hormone causes metabolic changes in the cell

How do hormones affect the body? (2)

* Help maintain chemical balances in the body
* Prepare the body for certain changes

What happens to most of the energy released from cellular respiration? (2)

* Wasted as heat energy
* Heat is then distributed by the blood to all parts of the body

What are arteries? (2)

Blood vessels that carry blood away from the heart and to the rest of the body. Distribute oxygen rich blood

What do large arteries do?

Branch many times to form smaller and smaller arteries until they form arterioles

What is the aorta?

The largest artery

Describe the composition of the artery walls:

* Thick, strong, muscular, and made of three layers
* Three layers = inner, middle, outer layer

Describe the composition of the inner layer of the artery wall:

Made of epithelial tissue (epithelium) and a smooth, thin sheet of tightly packed cells

Describe the composition of the middle layer of the artery wall:

* Made of elastic and muscle fibres

Describe the composition of the outer layer of the artery wall: (3)

* fibrous connective tissue
* nerves
* tiny blood vessels that nourish artery walls

Middle layer of artery major function: (4)

* Large arteries made mostly of elastic fibres = accommodate surges in blood pumped by walls
* Thick elastic walls stretch with changing blood pressure
* As arteries get smaller, blood pressure decreases = needs for elastic fibres to diminish
* Becomes mostly muscle fibres that contract to change size of artery regulating blood and pressure entering capillaries

Capillary formation: (3)

* Two outermost layers of arteries disappear as arteries branch into a network of capillaries
* Capillaries: thin walls = single layer of endothelial cells
* Average diameter is 7/1000 of a millimeter - wide enough to let a single RBC pass through

Capillary endothelium:

Substances in the blood + body tissue are only exchanged across capillary endothelium, not across walls of arteries + veins

Concentration of capillaries:

Depends on local needs for exchange of materials.

ex. muscles + kidneys remove waste products constantly need food + oxygen = well supplied with capillaries

lens of the eye, inactive tissue = none

Capillaries reunite:

Form venules → join to form larger and larger veins progressively having thicker layers of muscle + elastic fibres + connective tissye

Vein Structure: (3)

* Inner layer
* Middle layer (thinner than arteries)
* Outer layer

Vein inner layer consists of: (2)

* Epithelial tissue (epithelium)
* smooth thin sheet of tightly packed cells

Vein middle layer consists of: (2)

* Elastic fibres
* Muscle fibres

Vein outer layer consists of: (3)

* Fibrous, connective tissue
* Nerves
* Tiny blood vessels that nourish vein walls

Blood pressure with capillaries: (2)

* Blood forced into capillaries under pressure
* When it reaches arteries, pressure is very low

Role of veins: (3)

* Act as low-resistance channels for the flow of blood from tissue → back to heart
* Veins depend largely on the pressure exerted on them by surrounding tissue to return blood back to heart
* Most veins particularly in arms + legs have one-way valves that prevent back flow of blood into capillaries

Vein valves process: (2)

* While standing, a person unconsciously contracts muscles in legs to force blood through blood veins.
* When blood is not forced forward in the vein, the valve closes to prevent blood from flowing backwards

What does “the human heart is really 2 pumps working side by side” mean?: (4)

* A thick wall of muscle (septum) separates the heart into left + right halves.
* Both halves are divided into 2 chambers: atrium + ventricle
* Atrium collects blood returning to the heart + ventricle pushes blood out the heart → lungs or other parts of the body.
* Left pumps oxygenated blood, right pumps deoxygenated blood

Atria role: (2)

* Collects blood returning to the heart through the veins
* Thin muscles of their walls push blood a short distance → lower chambers; ventricles

Ventricle role:

Thick muscular walls of ventricles contract forcefully, pushing blood out the heart → lungs and body through arteries

Blood flow from tissue → heart:

Blood from any body tissue other than the lungs returns through either of 2 veins: superior vena cava, inferior vena cava.

Superior vena cava:

Drains blood from the arms, heart + upper parts of the body

Inferior vena cava:

Drains blood from the lower part of the body + legs

Blood flowing from venae cavae: (4)

* Having come from living breathing tissue, blood in veins = low oxygen content + high CO2 content
* Passes from superior/inferior venae cavae into right atrium
* Contraction of right atrium forces blood → lower camber; the right ventricle
* The AV valve between the two chambers prevents backward flow of blood from ventricle → atrium

Role of AV valve (tricuspid valve): (2)

* Consists of 3 flaps of tissue → forming a funnel shaped arrangement, narrow end extending into ventricle.
* Prevents backward flow of blood from ventricle → atrium

Blood flowing from venae cavae pt 2: (2)

* Pressure of blood in atrium forces valve open, but pressure in ventricle pushes flaps together, closing the valve
* Because of the tricuspid valve, a contraction of the right ventricle can force blood only out through the pulmonary trunk, the only artery departing from the right ventricle

Pulmonary semilunar valve:

* Located between right ventricle + pulmonary trunk, preventing back flow of blood.

Ventricle & pulmonary trunk:

* Shortly after leaving the right ventricle, the pulmonary trunk branches into 2 pulmonary arteries - each serving a different lung.

Blood flow + lungs: (2)

* In capillaries of the lungs, deoxygenated blood releases CO2 it picked up from body tissue + receives a fresh supply of oxygen
* After passing lungs, oxygenated blood → heart by the pulmonary veins which enter the left atrium

Left Atrium + blood flow: (4)

* Contraction of left atrium forces blood into left ventricle
* Another valve, bicuspid (mitral), prevents backflow of blood into atrium
* Contraction of left ventricle forces blood into aorta - largest artery of the body
* The aortic semilunar valve prevents backflow into the left ventricle when the ventricle relaxes

Bicuspid valve (mitral) function:

Prevents backflow of blood from left ventricle into atrium

Aorta + blood flow: (3)

* Branches of aorta carry oxygenated blood to all parts of the body except lungs.
* In the brain, a muscle, a gland, or an organ, oxygen is given off and CO2 is picked up from the tissues.
* The venules + veins that drain capillaries carry deoxygenated blood to either the superior or inferior vena cava which both return blood to the right atrium.

Human circulatory system 2 prominent blood circuits:

* Pulmonary system
* Systemic system

Pulmonary system:

Concerned with passage of blood from the heart → through lungs → back to heart

Systemic system:

Blood flow from heart → all the organs + parts of the body other than the lungs

Systemic circuit length:

60-90 seconds

Human circulatory system arrangement:

Efficient circulatory pattern that avoids mixing of oxygenated + deoxygenated blood

Each heartbeat requires: (2)

* Approx. 8/10 of a second at 75 beats/min (or 1 second at 60 beats/min)
* Can vary with age, exercise, health, + emotions.

A single heart beat consists of:

* A contraction of the atria followed by a contraction of the ventricles, then a period of relaxation of all 4 chambers.

What are systoles?

* The contraction phases of a heartbeat
* Four chambers contract: atria → ventricles

What are diastoles?

* The relaxation period in a heartbeat
* Follows after systoles of the four chambers of the heart.

Flow + timing of blood through the heart beginning with atrial systole:

* Atrial systole lasts 1/8 of a second, allowing blood to flow from atria → ventricles
* Atrial diastole follows after, lasting 7/8 of a second, allowing blood from inferior + superior venae cavae + pulmonary veins → atria.
* Atrial diastole starts at same time as ventricular systole which lats 3/8 of a second, forcing blood into pulmonary arteries + aorta.
* Ventricular diastole lasts through atrial systole of the next beat, + for half a second, all the chambers of the heart relax

Sinoatrial node (SA node): (4)

* A mass of specialized cells that initiate the contraction of the heart muscles of the atria + ventricles
* Located in the posterior wall of the right atrium, near the entrance of the superior vena cava
* Also called a pacemaker because it produces the impulse that starts each heartbeat
* The nerve impulse spreads quickly over both atria, causing the atrial muscles to contract

Atrioventricular node (AV node):

* The impulse reaches a second node of tissue, located between the ventricles but in contact with the lower portion of the right atrium
* Stimulation causes nerve impulses to be sent down the bundle of nerve fibres - Bundle of His
* (Receives impulse + gets stimulated causing nerve impulses to be sent down the ‘bundle of his’)

Bundle of His

Bundle of nerve fibres that branch into a pair of nerve fibres (purkinje fibres) that go down the septum of the heart - one of them surrounding the base of each ventricle)

Purkinje Fibres

Pair of nerves that surround the base of each ventricle, branches from the bundle of his

SA node + AV node ventricles:

Impulse that started in SA node, picked up by AV node reaches the muscles of the ventricles causing them to contract.

Cardiac output: (3)

* Defined as the amount of blood that flows from each side of the heart per minute.
* Amount of blood pumped by left side should be = to right side unless a dysfunction occurs
* cardiac output = heart rate x stroke volume

Two factors that affect cardiac output:

* Stroke volume
* Heart rate

What is stroke volume?

The quantity of blood pumped with each beat of the heart