PLTW HBS Heart

smooth muscle

composition - spindle-shaped cells containing actin and myosin filaments.

found - in the walls of hollow organs, such as the stomach, intestines, bladder, uterus, the walls of arteries and veins.

control - involuntary

notable characteristics - basically a contractile sheet, involved in behaviors like peristalsis, stomach churning, and bladder voiding

cardiac muscle

composition - specialized cells called cardiomyocytes and intercolated discs with gap junctions

found - heart

control - involuntary

notable characteristics - cells are joining by intercalated discs which enable coordinated contraction

skeletal muscle

composition - bundles of muscle fibers called fascicles

found - attached to bones of the arms, legs, neck, back, etc

control - voluntary

notable characteristics - are anchored to bone via tendons (connective tissue)

what is common to all structures composed of smooth muscle

involuntary, non-striated muscle cells

how does cardiac muscle differ structurally from smooth and skeletal muscle

has branching, striated fibers but also moves involuntarily. combination of the two types

why is the heart composed of muscle as opposed to another tissue type, like epithelium or connective tissue

must generate strong, rhythmic contractions to pump blood

describe the function of the heart

pumps blood through and around the system, maintaing blood pressure and body temperature

how does cardiac muscle enable heart function

enables through its unique properties (contractions, rhythms). skeletal muscle would fatigue too quickly and smooth muscle would be too slow

arteries

function - carry oxygenated blood away from the heart (except pulmonary arteries)

structure - 2-10mm diameter, thick walls (1-2 mm) with three layers, elastic fibers, smooth muscle, small lumen

relationship - thick elastic walls withstand high pressure from the heart and mainttain blood flow thorugh recoil

veins

function - return deoxygenated blood to the heart (except pulmonary veins)

structure - 5-30mm diameter, thinner walls (0.5-1mm), larger lumen, 3 layers but less muscle/elastic tissue and valves

relationship - larget lumen and valved facilitate low-pressure blood return against gravity

capillaries

function - exchange of gases, nutrients, and waste between blood and tissues

structure - 5-10 micromilimeter diameter, extremely thin walls, no muscle or elastic tissue

relationship - thin walls allow for efficient diffusion; small size maximizes surface area for exchange

why do you think the aorta is made of thicker muscle than the pulmonary artery?

the aorta has thicker msucle because it must withstand much higher pressure compared to the pulmonary artery

explain how the structure and location of veins can help them return blood to the heart

valves prevent backflow, skeletal muscle pump (surrounding muscles compress veins when contracted), respiratory pump (pressure changes during breathing), large lumen creates less resistance, extensive network with many collateral pathways

varicose veins

what - veins become enlarged, twisted, and visible under skin

how - form when valves weaken or fail, allowing blood to pool and cause venous distension

treatments - compression stockings, lifestyle changes, sclerotherapy, radio-frequency, ablation, laser treatments, surgical removal

why would someone who spends a lot of time on their feet be more likely to develop varicose veins

people who stand all day experience increased hydrostatic pressure in lower extremity veins, which stresses the valves and vessel walls over time, leading to valve failure and varicose veins

why do we not develop varicose arteries?

arteries have thicker, more muscular walls and no valves. they operate under higher pressure systems and don’t relay on the one-way valves to prevent backflow. arterial pressure itself maintains forward flow

how might the thickness of these muscle walls influence function?

the thickness of the muscle walls allows it to use more force to pump blood throughout the body

what do the colors blue and red typically signify regarding the circulatory system?

red signifies oxygenated blood and blue signifies deoxygenated blood in the circulatory system

consider the function of valves, as well as the prefixes bi and tri. what do you think the y shape or straight line you drew on each valve signifies?

the y shape signifies the tricuspid valve and the straight line signifies the bicuspid valve. a y represents the three ends of the tricuspid valve and the straight line represents the two ends of the bicuspid valve

which chambers would you label red? blue?

red - left atrium and ventricle

blue - right atrium and ventricle

are there any chambers that you would label purple

no, no chambers combine both oxygenated and deoxygenated blood

structurally, why would no chambers combine the blood

structurally it would not work becasue there would be no way to separate them to send oxygenated blood to the body

is this an advantage or disadvantage (not having combined chambers)

having separated chambers is an advantage because it allows for continuous movement of blood around the body

how do the pulmonary veins and arteries differ from the rest of the veins and arteries of the body

the pulmonary veins and arteries specifically bring blood from the lungs into the heart

how do the aortic and pulmonary valves differ from the tricuspid and bicuspid valves

aortic and pumonary valves prevent blood from traveling back into the heart while the tricuspid and bicuspid valves prevent blood from going into the different arteries/veins

why do you think the pulmonary artery splits at the top of the heart

the pulmonary artery splits at the top of the heart to separate blood into the left and right lung

list each structure in order in which blood passes

superior/inferior vena cava, right atrium, tricuspid valve, right ventricle, pulmonary valve, pulmonary artery, pulmonary veins, left atrium, bicuspid valve, left ventricle, aortic valve, aorta

do all heart chambers serve the same function

no, not all chambers serve the same function. ventricles are more muscular than the atria, and the left is thicker than the right

how does the structure of the chordae tendinae matter for their function

the structure of the chordae tendinae prevents the valved from collapsing under the pressure, preventing blood backflow

why is having valves essential to heart function

valves prevent blood from moving backward in the heart. this makes sure blood moves the proper way in the body

how does an enlarged heart impact function

having stretched and thin heart walls (due to an enlarged heart) prevents the heart from contracting with enough force to properly push blood around the body

why is a hole in the fetal heart necessary in utero

the hole in the heart allows for more oxygenated blood to travel around the body since a fetus’s lungs are non-functioning

for some people, the fetal hole never closes, what are some of the symptoms

shortness of breath, fatigue, migrains, heart palpitations, irregular heartbeat, stroke, decompression sickness

how does the structure of the heart contribute to its overall function

the structure of the heart allows for deoxygenated blood from the body to travel through the heart and become oxygenated in the lungs. the structure allows for quick and effective traveling of blood to the body

why would a five chambered heart not be an improvement over the four chambered heart

a five chambered heart would not be an improvement over the four chambered heart because it would cause uneven distribution of blood through the heart