Circulatory System

  • bring nutrients to cells

  • take wastes away

5 TYPES OF BLOOD VESSELS

heart → Aorta → arteries → arterioles → capillaries → venules → veins → vena cava → heart

BLOOD VESSELS

  • arranged to continuously carry blood from the heart to the tissues and return it from the tissues to the heart

    • arteries + arterioles → carry blood away from the heart

    • capillaries → exchange material with the tissues

    • veins + venules → return blood to the heart

Arteries

  • Structure + Functions

    • large thick elastic walls

    • surrounded by smooth muscle to control the diameter of the artery

    • carry blood away from the heart to tissues

Arterioles

  • Structure + Functions

    • branches of arteries

    • 0.2 mm diameter or smaller

    • mostly smooth muscle to allow for more control of the arteriole by the autonomic nervous system (involuntary)

Capillaries

  • Structure + Functions

    • connect the arterioles to venules

    • small vessels from the arteriole branches

    • narrow, one-cell thick-walled microscopic tube

    • exchange materials w/ tissue across the walls

      • gases + small molecules (oxygen, glucose (nutrients), CO2, + ammonia (waste))

    • in a capillary bed, some (many or most) of these sphincter muscles may be closed off so that less or more blood flows to that area

Venules

  • Structure + Functions

    • join together to form veins

    • drain the blood from capillaries and then join to form a vein

Veins

  • Structure + Functions

    • walls thinner than arterial walls

    • have valves allowing blood to flow only toward a heart when open and prevent backflow when closed

    • acts as a blood reservoir

LOCATION OF BLOOD

  • close to 60,000 miles (100,00 km)

  • veins → 75%

  • arteries → 20%

  • capillaries → 5%

ARTERY AND VEIN FUNCTIONS

Subclavian Artery and Vein (collar bones)

  • SA → bring blood to arms

  • SV → bring blood to the heart (RA)

Jugular Vein (head)

  • collects blood from the head to the heart (RA)

Carotid Artery (head)

  • blood from the heart to the head

Mesenteric Artery (small intestine)

  • blood from the heart to the small intestine

Anterior (top) and Posterior (top) Vena Cava

  • AVC → collects blood from the head, chest, and arms (blood enters RA)

  • PVC → collects blood from the lower body regions (blood enters RA)

Pulmonary (lungs)

  • takes oxygenated blood

  • PA → takes blood to lungs

  • PV → takes blood to the LA of the heart

Hepatic Vein (liver)

  • connect the blood vessels to the villi(s) to the liver

  • carries nutrient-rich blood to the liver for processing

    • ***portal system is a vascular system that begins + ends in the capillaries

Renal (Kidney)

  • RA → takes blood to kidneys from the aorta

  • RV → takes blood from the kidneys to the inferior (posterior) vena cava

Iliac (legs)

  • IA → takes blood to legs from the aorta

  • IV → takes blood from the legs to the inferior (posterior) vena cava

Coronary Artery and Vein

  • CA → arteries that serve the heart muscle directly with nutrients + O2

  • CV → brings blood from the heart to the RA

Aorta

  • largest artery

  • takes blood to major body regions and organs from the left ventricle

HEART

  • cone-shaped, muscular organ, the size of a fist

  • located between the lungs, directly behind the sternum

  • tiled so that the apex is directed to the left

  • myocardium

    • major portion of the heart; consists of cardiac muscle tissue

    • muscle fibers are branched and joined to one another tightly

  • endocardium

    • endothelial tissue that lines the inner surface of the heart

  • pericardium

    • the outside of the heart is covered with an epithelial and fibrous tissue

    • forms a sac called the pericardial sac, within which the heart is located

      • contains liquid to lubricate the heart

  • left + right separated by the septum

  • 4 chambers

    • two upper, thin-walled atria

      • smaller

    • two lower thick-walled ventricles

  • valves

    • direct the flow of blood and prevent a backflow

    • atrioventricular valve

      • valves that lie between the atria and ventricles

      • supported by fibrous strings called chordae tendineae

        • supported by muscular projections of the ventricular wall

      • right side is tricuspid valve

        • 3 cusps or flaps

      • left side is bicuspid valve or mitral

        • 2 cusps or flaps

    • semilunar valves

      • between the ventricles and their attached vessels

HEARTBEAT

  • beats independently of any nervous stimulation (intrinsic)

  • nodal tissue: contains both muscular and nervous characteristics, located in two regions of the heart

    • SA (sinoatrial) node: found in the upper dorsal wall of the right atrium

      • pacemaker → initiates the heartbeat and automatically sends out an excitation impulse every 0.85 sec to cause the atria to contact.

      • keeps the hearbeat regular

        • if SA node works improperly, an artificial pacemaker can automatically give an electric shock to the heart every 0.85 sec

    • AV (atrioventricular) node: found in the base of the right atrium near the septum

  • systole → contraction of heart muscle

    • atria contract

  • diastole → relaxation of heart muscle

    • ventricles contract

  • atrial systole → ventricular systole

  • lub-DUPP → sound heard caused by vibrations of the heart when the valves close

    • lub → slightly longer sound from the closing of atrioventricular valves

    • DUPP → shoter and sharper sound from the closing of semilunar valves

  • 120/80 mmHg

  • each heartbeat is a cardiac cycle

  • process:

    • when the heart beats, first the two atria contact at the same time

    • two ventricles contract at the same time

    • all the chambers relax

HEARTBEAT CONTROL

  • Intrinsic Control → control from within the heart

    • the rhythmic contraction of the heart is due to the internal conduction system made possible by nodal tissue

    • the two nodal regions in the heart and pukinje fibers:

      • sinoatrial (SA) node → the pacemaker

      • atrioventricular (AV) node

  • Extrinsic Control → control from outside of heart (brain)

    • even though the heart can keep a steady beat on its own, how fast it goes (heart rate) is under nervous control

    • medulla oblongata → heart-rate center which can speed up or slow down the heart rate due to stimuli received by the autonomic nervous system

      • system will adjust the heart rate based on factors such as stress, oxygen level, and blood pressure

  • Tissues

    • Sino-atrial node (SA)

      • located in upper dorsal wall of right atrium

      • sends signals every 0.85 sec

      • causes both atria to contract and initiate the heartbeat

    • atrioventricular node (AV)

      • located at the based of right atrium near septum

      • when it receives the SA node pulse, it sends its own pulse to cause ventricles to contract.

      • if its alone, it can cause heart to beat but much slower (40-60 bpm)

    • purkinje fiber

      • located throughout the ventricles

      • special conducting fibers that take the AV node impulse to the ventricles causing them to contract

      • help insure the contractions begin at the base of the ventricle and move up like a wave

HEART STRUCTURE

Left + Right Atria

  • LA → stores + passes blood to the LV

  • RA → stores + passes blood to the RV

Left + Right Ventricle

  • LV → pumps blood to all body parts except the lungs

  • RV → pumples blood to the lungs

Coronary (A&V)

  • CA → arteries that serve the heart muscle

  • CV → veins that bring blood from the heart to the right atrium of heart

Anterior & Posterior Vena Cava

  • superior/anterior VC → carries blood from head, chest, arms to RA

  • inferior/posterior VC → carries blood from lower body regions to RA

Aorta

  • largest artery (dips down behind the heart)

  • sends blood to the major body regions

Pulmonay (A&V) (arteries + veins)

  • PA → take deoxygenated blood to the lungs

  • PV → takes oxygenated blood to the LA of the heart

Pulmonary Trunk

  • divides into pulmonary arteries which take blood to the lungs

Atrioventricular Valves

  • separate the atria from the ventricles and prevent backflow

Chordae tendineae

  • support the valves + prevent them from inverting

Semilunar valves

  • allow blood to enter the pulmonary artery + aorta

  • prevent backflow of blood

septum

  • separates the left and right side of the heart

BLOOD PRESSURE

MEASURING

  • 120 mm Hg is how high a column of mercury would be pushed as soon as the ventricles contract

  • when ventricles relax, pressure decreases down to 80 mm Hg.

  • it would continue to decrease except that at this time, the ventricles fioll up and contract again pushing the pressure up to 120 mm Hg (again).

  • Why does pressure drop?

    • elastic nature of the arteries

    • blood being distributed throughout the body

    • blood pressure drops as the blood is distributed to a “low” of about 10mm Hg in the capillaries

  • By the time the blood reaches the venules and beins it does not have enough pressure to reach the heart on its own

    • 1. minute contractions of the skeletal muscle will push the blood back to the heart

    • 2. valves prevent backward flow

  • pulse→ the alternate expanding and recoiling of an arterial wall that can be felt in any artery near the surface of the body

    • eg) radial atery in the wrist

    • eg) carotid atery in the neck

    • process:

      • left ventricle contracts and sends blood out into the aorta

      • the elastic walls of the arteries swell and immrediately recoil

      • the alternate expanding and recoiling of an arterial wall can be felt as a pulse in any artery that is close to the surface

  • blood pressure → pressure of the blood against the wall of a vessel due to the pumping of the heart

    • measured with an instrument called a sphgmomanometer

      • a hollow cuff attached to a pressure gauge

    • systolic blood pressure → highest arterial pressure due to blood being ejected from the heart

    • diastolic blood pressure → lowest arterial oressure when the ventricles are relaxing

    • normal bp → 120mmHg over 80mmHg (120/80) in the brachial artery of the arm

      • decreases with distance from left ventricle

      • a sharp drop in blood pressure when the artieroles reach the capillaries

        • correlated with the increase in the total cross-sectional area of the vessels as blood moves through artiers, arterioles, and then into capillaries

        • # capillaries > # arterioles > # arteries

    • movement of the blood through the venous system is due to skeletal muscle contraction

      • when the muscles contract, they press agains the weak walls of the veins

        • causes the blood to move past a valve and will not fall back

  • ECG waves

    • P wave → indicates that the atria are about to contract

    • QRS wave → indicates that the ventricles are about to contract

    • T wave → indicates that the ventricles are about to relax (recovering of ventricular muscle fibers)

BLOOD COMPONENTS

  • humans are 70% water by body weight

    • most water is within cells, while a smaller amount is found within:

      • tissue fluid (surround cells)

      • lymph (within lymph vessels → part of the lymphatic system that cleans the immune system and small intestine)

      • blood vessels

  • blood is required by the body to maintain homeostasis

    • it is a connective tissue

    • Functions:

      • transport (of gases, wastes, and nutrients)

      • clotting (to seal injuries)

      • infection fighting

  • TWO MAIN PARTS:

    • PLASMA

      • the liquid portion of the blood

      • makes up 55% of blood volume

      • contains water and organic and inorganic substances (proteins, gases, sats, nutrients, wastes)

    Plasma Constituent

    Function

    Source

    water

    maintains blood volume and transports molecules

    absorbed from large intestine

    plasma proteins

    1. Albumin

    2. Fibrinogen

    3. Globulins

    1. maintain blood osmotic pressure and pH

    2. transport

    3. clotting

    4. fight infection

    1. liver

    2. liver lymphocytes

    Gases

    1. oxygen

    2. carbon dioxide

    1. cellular respiration

    2. the end product of metabolism

    1. lungs

    2. tissues

    Nutrients

    1. fats

    2. glucose

    3. amino acids

    4. etc.

    food for cells

    absorbed from intestinal villi

    Salts

    1. maintain blood osmotic pressure/pH

    2. aid metabolism

    absorbed from intestinal villi

    Nitrogenous wastes, Urea

    excreted by kidneys

    liver

    Hormones, Vitamins etc.

    Aid metabolism

    Varied

    • FORMED ELEMENTS

      • the “solid” part of blood

      • consists of red blood cells, white blood cells, and platelets

Formed Element

AKA

Function

Source

Red blood cells (over 95% of formed elements)

Erythrocytes

transport oxygen and help transport carbon dioxide

red bone marrow

white blood cells (granular and agranular)

Leukocytes

Fight Infection

Red bone marrow and lymph tissue

Platelets

Thrombocytes

Aid clotting

Red bone marrow

CAPILLARY EXCHANGE

  • blood pressure vs. osmotic pressure

  • movement of fluid controlled by:

    • blood pressure → Blood vessel tends to push molecules out of the blood

      • force blood against vessel walls

      • causes H2O to move from blood to tissues

    • osmotic pressure → the opposing force trying to force molecules into the blood

      • created by salts + plasma proteins

      • causes H2O to move from tissue fluid to blood

  • osmotic pressure is basically constant, the blood pressure changes

  • 3 capillaries:

    • At the ARTERIAL SIDE: BP > OP

      • water, oxygen, and glucose tend to leave the blood

    • At the VENOUS END: OP > BP

      • water, ammonia, and carbon dioxide tend to enter the bloodstream

    • In MIDDLE: BP = OP

      • molecules diffuse according to their concentration gradient

      • nutrients leave the blood and enter cells

      • wastes will diffuse out of cells and enter the blood

VASCULAR PATHWAYS

  • cardiovascular system is separated into two parts:

    • PULMONARY CIRCUIT

      • the path of blood from the heart through the lungs

        • deoxygenated blood from all tissues collects in the right atrium;

        • pumped to the right ventricle;

        • sent to the pulmonary trunk;

        • which divide up into arterioles of the lungs

        • Arterioles take blood to the pulmonary capillaries; where CO2 and O2 are exchanged

        • The oxygenated blood enters the pulmonary venules, then the pulmonary veins, and finally back to the left atrium

    • SYSTEMIC CIRCUIT

      • includes all blood vessels except those in the pulmonary circuit

      • takes blood from the left ventricle, through the tissues and organs of the body, and back to the right atrium

      • veins carry deoxygenated blood

      • arteries carry oxygenated blood

path of blood to kidneys:

left ventricle → aorta → renal artery → renal arterioles → capillaries → venules → renal vein → inferior vena cava → right atrium

PATH OF BLOOD THROUGH FETUS

  • Blood collects in the right atrium

  • blood goes into left atrium through oval opening + right ventricle through atrioventricular valve

  • right ventricle to pulmonary artery. Most of blood will go through arterial duct into aorta

  • Aorta to tissue. Umbilical arteries lead to placenta, where excange of gases and nutrients take place

  • umbilical veins carries O2 rich blood.

    • it enterse the venous duct, passes through liver

  • venous duct joins with inferior vena cava (it mixes here with deoxygenated blood) and this mixed blood goes back to the heart

DIFFERENCES BETWEEN FETAL AND ADULT SYSTEMS

  • heart develps in 3rd + 4th week in uterus

  • at 8 weeks, the embryo’s organ systems, (eg. heart) are functioning

  • during the fourth month, fetal heartbeat is loud enough to be heard with stethoscope

  • Differences:

    • fetus are not using their lungs; no blood is needed to go to lungs

    • fetus must get all its nutrients from mom, as well as let her take care of its wastes.

FOUR FEATURES NOT PRESENT IN ADULTS TO SOLVE FETUS PROBLEMS:

  1. oval opening (foramen ovale)

    • opening between the two atria act like a valve

    • some of the blood from the right atrium is therefore pumpled through this flap and into the left atrium

    • allows the pulmonary circuit to by bypassed

    • if oval opening doesn’t close after birth, it can causing mixing of blood and ‘blue babies’

      • can be corrected with heart surgery

  2. Arterial Duct (ductus arteriosus)

    • connects pulmonary artery and aorta

    • allows the blood being pumped out of the heart to the lungs, which will be directed away from the lungs and into the aorta

    • function is to bypass the pulmonary circuit

  3. Umbilical Arteries and Veins

    • vessels that travel to and from the placenta (a membrane shared by the mother and baby across which gases, nutrients, and wastes are exchanged)

    • the umbilical arties are grafted to the iliac arteries

  4. Venous Duct (ductus venosus)

    • connects umbilical vein to the vena cava to bring the blood back to the baby’s heart

    • attaches right at the babies liver, but bypasses most of the liver

      • this is why chemicals ingested by the mother can seriously affect the baby!