The circulatory system Flashcards
Main Functions of the Circulatory System
- TRANSPORTS gases, nutrients and wastes.
- REGULATES internal temperature and transports hormones.
- PROTECTS against toxic substances, and blood loss from injury (via clotting).
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Major Structures/Components
Heart – muscular organ pumps blood through body to generate blood flow
Blood vessels – “roadway” though which blood moves
Blood – carries nutrients, oxygen, CO2, water, and others through the body
Major Circulatory
Pathways, Two Circuits:
○ Pulmonary – Blood moving between the heart and lungs
○ Systemic – Blood moving from the heart to the rest of the body
Heart Structure
○ Composed of cardiac muscle tissue
○ Contractions are rhythmic and involuntary
○ Surrounded by a sac – Pericardium
○ Fluid-filled membrane that acts as a shock absorber and prevents friction
○ Heart is tipped slightly to the left of chest
Atria
Fill with blood returning either from the body or lungs.
Right atrium and ventricle handle deoxygenated blood (BLUE)
Left atrium and ventricle handle oxygenated blood (RED)
ventricles
receive blood from atria and pump it to body or lungs.
Septum
A wall of tissue that separates left and right atria/ventricles
Valves
○ Ensure that blood flows only in one direction
-tricuspid, mitral, aortic, pulmonary
Heart Sounds
○ Valves closing = heart sounds
○ As ventricles contract – the semilunar valves open
and AV valves close – LUB
○ As ventricles begin to relax (start filling again) – the
semilunar valves close AV valves open, - DUB
Vena Cavae and Aorta
Vena cavae - two large vessels open into the right atrium
○ superior: oxygen-poor blood from upper body
○ inferior: oxygen-poor blood from lower body
Aorta – oxygen rich blood to the rest of the body (very large!)
Blood Vessels: Arteries
o Typically carry oxygenated blood.
o Carry blood away from the heart
o Thick, highly elastic walls to keep blood flowing in right direction (allows arteries to contract)
o Composed of three layers.
Blood Vessels: Veins
o Typically carry deoxygenated blood
o Carry blood back to the heart
o Thin, rigid walls (do not contract on their own)
o One-way valves (important to counteract the force of gravity)
o Composed of three layers
Varicose Veins
occur when the leaflets of valves fail to close properly, causing blood to flow backwards and pool in the veins
Blood Vessels: Capillaries
o Connect arteries and veins to tissues
o Composed of a single layer of cells
o Much smaller and more widespread than arteries and veins
o The site of gas exchange in the circulatory system
Arteries and veins
arteries contain oxygenated blood, while
veins contain deoxygenated blood.
EXCEPTIONS
The pulmonary arteries carry deoxygenated blood
o (from the right ventricle to the lungs)
The pulmonary veins carry oxygenated blood
o (from the lungs to the left atrium)
Path of blood flow through the body: Deoxygenated
- Once depleted of oxygen, blood returns to the right atrium of the heart through the superior and inferior vena cava
- Blood moves through the right atrium to the right ventricle, where it is then pumped out of the heart via pulmonary arteries to the lungs. Here, CO2 will be exchanged for O2
Path of blood flow through the body: Oxygenated
- Oxygenated blood travels back to the heart where it enters the left
atrium through pulmonary veins. - Blood flows into the left ventricle and is pumped out of the heart via the aorta, where it then travels to other areas of the body.
electrocardiogram (ECG):
used to record the electrical activity of the heart:
-P = contraction of atria
-QRS = contraction of ventricles
-T = recovery of ventricles
Blood Pressure
-the pressure exerted against the walls of the heart as blood is transported throughout the body
o Measured as a ratio of systolic/diastolic pressure (120/80 is normal)
o Maximum pressure during ventricular contraction = systolic pressure
o Minimum pressure before ventricular contraction = diastolic pressure
Cardiac Output
the amount of blood pumped by the heart per unit of time
o Used to indicate extent of oxygen delivery to tissues
o Affected by heart rate (beats per minute) and stroke volume (amount of blood forced out of the heart with each beat, the greater the stroke volume)
Thermoregulation
The maintenance of body temperature within an acceptable range.
* Human’s typical body temperature is ~37 degrees Celcius
* It is a survival mechanism used to help protect us when we’re in extreme environments of heat or cold
rise in body temperature:
- The hypothalamus in the brain sends a signal to the sweat glands to initiate sweating, which leads to evaporative cooling
- Nerves send a message to the capillaries to dilate, allowing more
blood flow to the skin. - More blood flow means more heat can be lost through the skin before it returns to our body’s core.
- Body cools down
drop in body temperature:
- The hypothalamus in the brain sends a signal to internal organs to increase body temperature, and to initiate shivering AND
- Nerves send a message to the smooth muscles in our arteries to constrict, allowing less blood flow to the skin.
- Less blood flow means less heat is lost through the skin before it returns to our body’s core.
- The body warms up
Heart Disorders: Atherosclerosis
- This condition occurs when excess lipids in someone’s arteries begin to aggregate (clump together) and stick to the inner walls of arteries.
- This limits blood flow, can lead to high blood pressure
- Sometimes, blood will clot and block the artery completely
Heart Disorders: Arteriosclerosis
o Hardening of the arteries due to a buildup of plaque
o Caused by lack of exercise, smoking, and/or a diet high in fat
o Leads to decreased blood flow and increased blood pressure
o Symptoms include chest pain, blood clots,
treatments for Arteriosclerosis
o Aspirin (prevents platelets from sticking together, reducing the formation of blood clots)
o Angioplasty (surgical procedure wherein a tube is inserted into a clogged artery and inflated, forcing the artery to open)
o Coronary bypass (segment of a healthy artery/vein is used to create a new pathway from the aorta to an unblocked portion of the blood vessel, thereby “bypassing” the blocked segment)
Congenital Heart Defects
Congenital Heart Defects
o Structural defects present from birth.
o May be genetic, or due to drug/alcohol use during pregnancy.
o Examples:
* Valve defects (leaky valve leads to heart murmur)
* Septal defects (hole in septum leads to mixing of oxygenated and deoxygenated blood)
Aneurysm
- This condition occurs when a bulge forms in the wall of a
weakened blood vessel, usually an artery - Often occurs due to atherosclerosis
- It will result in a thinner artery wall and become at risk for a
rupture of the artery
high blood pressure (Hypertension)
- High blood pressure over the long term can:Weaken arterial walls
- Destroy capillaries in body tissue (i.e. nephrons in kidneys, coronary arteries, etc.)
- Diet often a primary factor
- Increased salt intake can cause blood pressure to rise
Heart attack symptoms in women:
- Neck, shoulder, upper back, or abdominal discomfort- often triggered by stress or
anxiety. More likely to occur during rest. - Shortness of breath
- Nausea or vomiting
- Sweating
Heart attack symptoms in men:
- Intense chest pain or pressure that may extend to arms- often triggered by physical activity. Tends to go away with rest.
- Shortness of breath
