Circulatory System: Blood Vessels and Heart Functions

Blood vessels

Transport blood, nutrients & waste throughout the body.

Capillaries

Connect the arterioles to venules and exchange material with tissues.

Heart

4 chambered organ made up of mostly cardiac muscle that pumps blood to vessels.

Blood

Tissue that helps function in transport, clotting, and fighting infections.

Arteries

Carries blood away from heart and has thick walls composed of smooth, elastic muscle fibers.

Arterioles

Small branches of arteries that lead to capillaries.

Functions of arteries

Strength to constrict and dilate, withstand blood pressure, and provide O2 and nutrients.

Functions of capillaries

Microscopic tubes that allow for exchanges via diffusion and are surrounded by sphincter muscles.

Veins

Carry blood back towards heart and have valves to prevent backflow.

Venules

Drain blood from capillaries and join to form veins.

Blood carried by arteries

Most arteries carry oxygenated blood.

Blood carried by veins

Most veins carry deoxygenated blood.

Exceptions to blood types in vessels

Pulmonary vein and umbilical vein.

Order of cross-sectional vessels

1. Capillaries 2. Venules 3. Arterioles 4. Veins 5. Arteries.

Heart functions

Muscular organ that pumps blood and is surrounded by the pericardium.

Double pump of the heart

Right side pumps blood to lungs, left side pumps blood to rest of body.

Septum

Thick wall that separates the two sides of the heart to prevent mixing of oxygen and deoxygenated blood.

Purkinje fibers

Spreads electrical stimulation from AV node to ventricles and causes ventricles to contract.

Path of blood through the heart

1. Deoxygenated blood enters the right atrium through the superior and inferior venae cavae (bodies largest veins)

2. Right atrium contracts, forcing blood through the tricuspid valve and into the venae cavae

3. Right ventricle contracts, sending blood through the pulmonary trunk

4. Pulmonary trunk divides into pulmonary arteries, which take the deoxygenated blood to lungs’ capillaries

5. In the lungs, CO2 diffuses out of the blood, oxygen diffuses into the blood. Blood is now oxygenated (gas exchange)

6. Oxy blood feeds into pulmonary veins which takes blood from lungs to left atrium

7. Left atrium contracts, forcing blood through bicuspid valve into left ventricle

8. Left ventricle contracts, forcing blood through semilunar valve into the aorta (bodies largest artery)

9. The aorta divides into smaller arteries, which carry oxy blood to all body tissues

Deoxygenated blood

Blood that enters the right atrium through the superior and inferior venae cavae.

Right atrium

Chamber that contracts to force blood through the tricuspid valve into the right ventricle.

Tricuspid valve

Valve that allows blood to flow from the right atrium to the right ventricle.

Right ventricle

Chamber that contracts to send blood through the pulmonary trunk.

Pulmonary trunk

Vessel that divides into pulmonary arteries to carry deoxygenated blood to the lungs.

Gas exchange

Process in the lungs where CO2 diffuses out of the blood and oxygen diffuses into the blood.

Oxygenated blood

Blood that is returned to the left atrium via pulmonary veins after gas exchange.

Bicuspid valve

Valve that allows blood to flow from the left atrium to the left ventricle.

Left ventricle

Chamber that contracts to force blood through the semilunar valve into the aorta.

Aorta

The body's largest artery that carries oxygenated blood to all body tissues.

Systole

Phase of the heartbeat characterized by the contraction of heart muscles.

Diastole

Phase of the heartbeat characterized by the relaxation of heart muscles.

Lub

Sound produced by the closing of AV valves during atrial contractions.

Dub

Sound produced by the closing of semilunar valves during ventricular contractions.

Nodal Tissue

Tissue in the heart that has characteristics of both nervous and muscular tissues, controlling the heartbeat.

SA node

Sinoatrial node located in the upper back wall of the right atrium that initiates the heartbeat.

AV node

Atrioventricular node located in the base of the right atrium that receives signals from the SA node.

Purkinje fibers

Fibers that carry the contraction signal to the ventricles, causing them to contract.

Medulla oblongata

Part of the brain that regulates heart rate based on stimuli from the autonomic nervous system.

Pulse

The expanding and recoiling of arterial walls that can be felt in major arteries.

Blood pressure

The pressure of blood against the walls of vessels created by the heart's pumping.

Diastolic blood pressure

The lowest arterial pressure occurring when the ventricles relax.

Hypertension

High blood pressure caused by factors such as excessive salt intake, atherosclerosis, and stress.

Hypotension

Low blood pressure that can be detrimental to kidney function.

Fetus

Does not breathe air or eat nutrients, therefore it gets all O2 and nutrients from mother via placenta.

Amniotic fluid

The fluid that fills the mother's womb where the fetus is located.

Fetal circulatory system

Allows blood to bypass the lungs, exchanging nutrients and wastes at the placenta.

Foramen ovale

An opening between the atria covered by a flap that passes blood from the right atrium to the left atrium, bypassing pulmonary circulation.

Ductus arteriosus

Connects the pulmonary artery with the aorta, directing blood being pumped to the lungs to the aorta, bypassing pulmonary circulation.

Umbilical arteries and veins

Blood vessels that travel to and from the placenta via the umbilical cord, with arteries carrying deoxygenated blood and veins carrying oxygenated blood.

Ductus venosus

Connects the umbilical vein to the inferior vena cava of the baby, passing blood from the umbilical vein and bypassing the liver to the inferior vena cava.

Fetal circulatory features after birth

Arterial/venous ducts disintegrate; all fetal modifications close due to pressure of air outside the womb, ensuring no mixing of oxygenated and deoxygenated blood.

Blood passage from placenta to baby

Placenta - umbilical vein (oxy) - venous duct - inferior vena cava - right atrium - foramen ovale - left atrium - left ventricle - aorta - iliac artery - umbilical artery (deoxy) - placenta.

Human body water content

Humans are 70% water by body weight, mostly found in cells as tissue fluid, lymph, and blood vessels.

Blood

A liquid connective tissue that functions in transport of gases, wastes, nutrients, clotting, and fighting infection.

Plasma

The liquid portion of blood that makes up 55% of blood volume, containing water, proteins, and dissolved substances.

Red blood cells (erythrocytes)

Transport O2 (and some CO2), formed in red bone marrow, making up 95% of formed elements.

White blood cells (leukocytes)

Fight infection (immune response), formed in bone marrow, classified based on appearance (granular or agranular).

Platelets (Thrombocytes)

Function in blood clotting.

Functions of plasma

Maintains blood volume, transports molecules, and contains constituents like water, plasma proteins, gases, nutrients, salts, wastes, hormones, and vitamins.

Albumin

A plasma protein that maintains blood osmotic pressure and pH.

Fibrinogen

A plasma protein involved in clotting.

Globulins

Plasma proteins that fight infection.

Blood proteins

Required for the transport of many molecules, contribute to the viscosity of blood, and osmotic pressure, which maintains blood volume.

Platelets (Thrombocytes)

Used in blood clotting (coagulation). Made from the fragmentation of large cells called megakaryocytes in red bone marrow.

Platelets

More than a trillion in the blood.

Blood clotting

Requires: Platelets, Prothrombin, Fibrinogen.

Prothrombin and fibrinogen

Plasma proteins made in the liver.

Vitamin K

Needed to produce prothrombin.

Red Blood Cells (Erythrocytes)

30 trillion RBCs in an adult; 300 million in one drop of blood.

Red Blood Cells

Small, biconcave, disk-shaped cells without nuclei (to allow for more room for oxygen).

RBC production

Produced by stem cells in red bone marrow of the skull, ribs, vertebrae, and long bones.

Oxygen levels

Determine the rate of RBC formation.

Low oxygen levels

Cause the kidneys to produce renal erythropoietic factor (REF), which stimulates RBC production in bone marrow.

RBC lifespan

RBCs live for 120 days and are destroyed in the liver and spleen.

Iron recovery

Iron is recovered and reused; heme portion is degraded and excreted by the liver in bile pigments.

Hemoglobin (Hb)

Blood protein found inside RBCs (not in plasma).

Hemoglobin structure

Quaternary protein with four amino acid chains, each containing an iron-heme group.

Oxygen-carrying capacity

Hemoglobin increases blood's oxygen-carrying capacity by 60 times.

Oxyhemoglobin (HbO2)

Is bright red (found in arteries).

Deoxyhemoglobin (Hb)

Is darker and purplish (found in veins).

White Blood Cells (Leukocytes)

The body's second line of defense against infection.

White Blood Cells

Larger than RBCs, have a nucleus, and appear white.

Antibodies

Produced by white blood cells to fight infections by targeting antigens (foreign substances).

Phagocytosis

The process by which white blood cells engulf pathogens.

Lymphatic System

A one-way system that starts in the tissues and empties into the cardiovascular system.

Lymph

The fluid in vessels formed from bits of blood and other body fluids (interstitial fluid/tissue fluid) that collect in the spaces between cells.

Functions of the Lymphatic System

1. Transport of excess tissue fluid back to the cardiovascular system. 2. Absorption of fats from the intestine and transport to blood (lacteals). 3. Immune function by cleansing lymph and producing lymphocytes.

Lymph vessels

Consist of lymph capillaries and lymph veins (which have valves).

Right Lymphatic Duct

Drains the upper right portion of the body and empties into the right subclavian vein.

Thoracic Duct

Drains the rest of the body and empties into the left subclavian vein.

Lacteals

Blind ends of lymph vessels in the villi of the small intestine where products of fat digestion enter.

Lymph nodes

Small oval or round structures that occur along strategic places on lymph vessels. They produce and store lymphocytes and filter lymph of damaged cells and debris.

Spleen

Located behind the stomach. Contains white blood cells and stores blood.

Thymus gland

Located in the upper thoracic cavity, functions in the production and maturation of some lymphocytes. Decreases in size with age and may be a factor in aging.

Aorta

Heart to all other major arteries

Carotid Artery

Heart to head

Pulmonary artery

Heart to lungs

Subclavian artery

Heart to arms

Renal artery

Heart to kidneys

Illiac artery

Heart to legs