Heart and Circulatory

Blood Functions:

transport nutrients, hormones, enzymes and other critical substances

removes waste

protects body against infections

stabilize acid-base balance

regulate body temperature

Role of Cells:

• platelets (thrombocytes) - blood clotting
• white blood cells (leukocytes) - protection against pathogens
• red blood cells (erythrocytes) - deliver oxygen and remove carbon dioxide

Hemopoeisis- formation of blood cells

red blood cells- produces all types of blood cells

lymphatic tissue- produces lymphocytes like b and t cells

red blood cells (erythrocytes) :

• oxygen binds to hemoglobin, removes carbon dioxide
• mature rbc had no nucleus/no mitosis
• broken down in liver and spleen into iron, bilirubin, amino acids (these are re-used)

white blood cells (leukocytes)

• granulocytes :
  • neutrophils: most effective and abundant phagocytes
  • eosinophils: allergic reactions and parasitic infections
  • basophils: least abundant; secretes substances to help reduce blood clotting during inflammation
• agranulocytes :

- lymohocytes:

→ t lymphocytes: attack infected or cancerous cells (recognized specific antigens)

→ b lymphocytes: produce antibodies against specific antigens

- monocytes:

→ turn into macrophages after entering tissue; very effective phagocytes

• platelets (thrombocytes)

  cell fragments involved in blood clotting (hemostasis)

stages of hemostasis:

• vascular spasm: smooth muscle in blood vessel spasms; blood vessel constricts and blood flow slows
• formation of platelet plug: collagen fibers cause platelets to be sticky causing them to stick with each other forming a temporary plug
• formation of blood clot: proteins (clotting factors) start a chain reaction that ends in production of fibrin; soluble proteins in plasma are converted to insoluble threads-- fibrin; fibrin threads from a web at the site for protection

factors that discourage blood clots:

• smooth endothelium- prevents sticking
• blood flow- normal blood flow prevents enzymes from forming fibrin
• anticoagulants- released some cells(like basophils) to prevent the formatin of fibrin

Blood types : rbc classified into four possible blood types

• antigen- molecule that can be recognized by immune system
• blood type- antigen present on person’s rbcs
• antibodies- opposite of blood type/antigens

RH group

• presence= +
• absence= -
• negative types have antibodies to RH; positive types dont

THE HEART :pumps blood through body via two routes that have distinct functions. heart is located in thoracic cavity in the mediastinum

• pulmonary circ- delivers deox blood to lungs to pick up more oxygen and expel co2
• systemic circ- delivers oxy blood to tissues in the whole body along w nutrients, hormones, etc.

anatomy of the heart:

• pericardium- connective tissue that protects, anchor and reduces friction (serous fluid)
• endocardium- inner epithelial lining
• cardiac muscle - contracts heart
• epicardium- outer epithelial lining

heart chambers: receive and discharge blood

• atria ( 2 right and left):

  → receive blood; move blood to ventricles (thin muscle lining)

• ventricles (2 right and left)

  → discharge blood; move blood to body (thick muscle lining)

two sides of the chambers:

• left atrium- receives OXY blood from lungs then moves it to ventri
• left ventri- pumps OXY blood to body
• right atrium- receives DEOXY blood from body then moves it to ventri
• right ventri- pumps DEOXY blood to lungs

heart valves

• atroventricular valves (av valves)-prevents backflow from ventris to the atrium
• tricuspid valve- right av valve
• mitral/bicuspid valve- left av valve
• semilunar valves- prevents backflow from the great arteries to the ventric; ensures blood flows right direction
• pulmonary valve- between right ventri and pulmonary artery; blood stays in pulmonary artery
• aortic valve- between left ventri and aorta; blood stays in aorta

Valve mnemonic- TOTALLY PASSING MY ANATOMY CLASS/ TriPulMit Ao

vena cava vessels: carries deoxy blood to the heart from the body; empties into right atrium

• superior vc- blood from upper body
• inferior vc- blood form lower body

aorta vessels: carries oxy blood to every organ into body (Away from heart); leaves from the left ventri

pulmonary vessels:

• pulmonary arteries- carry blood away from heart to right ventri to lungs; deoxy blood; picks up oxygen and returns via..
• pulmonary veins- carry blood to the heart to left atrium from the lungs; oxy blood

heart sounds

• LUB- closing of av valves ( mitral + tricuspid)
• DUB- closing of semilunar valves (pulmonic + aortic)

cardiac conduction- heart generates its own electrical impulses; these impulses give the signal for heart muscles to contract and move blood through the heart

• pacemaker cells- heart generates action potentials through this ; SA node begins process

• Sinoatrial (SA node)- where cardiac impulses arise; located in right atrium

  → electrical impulses travelling through heart allows it to pump blood

  →sa node starts the signal causes atria to contract

  → signal passes along av node - bundle of his- bundle branches- purkinje fibers ; cause ventris to contract

• Bundle of fibers carry impulse to left atrium

• atrioventricular (AV valve)

• Bundle of His

• right and left bundle branches- signal then travels to right and left branches that reach ventricle

• Purkinje fibers- signal finally arrives along the muscular walls of each ventricle

electrocariogram (ecg/ekg)

• traces the overall electrical activity of heart/ movement of impulses from SA node to purkinje fibers
• represents numerous action potentials that occur in atria and ventircles which ultimately cause the heart muscles to contract

cardiac cycle- series of events from the beginning of one heartbeat to the beginning of the next; consists of a series of changes in:

• pressure- influencs heart vales
• contractions of the myocardium- due to impulses; systole (contraction) and diastole (relaxation)

cardiac cycle phases

• atria fill w blood; moves into ventricles
• atria contract (atrial systole)
• ventris contract (ventricular systole)
• ventricular ejection
• ventricular relaxation (ventricle diastole)

Heart: the basic principles

• contractions of myocardium: reason why blood moves between chambers and into vessels
• systole and diastole refers to: ventricles
• conduction system (pacemaker cells): where the stimulation of the muscles to contract comes from
• pressure changes in chambers and vessels: why valves open and closes
• pressue: comes from the volume of blood and muscle contractions

cardiac output: amount of blood heart pumps in 1 minute

→ determined by heart rate and stroke volume

→ avg cardiac outpic = 5 to 6 litres of blood

heart rate = number of beats per minute

→ avg is 60 to 100 ; depends on fitness, age and biological sex

→ nervous system and hormones can still affect how fast the heart beats (heart rate)

medulla oblongata: cardiac center; increase or decreases heart rate depending on info from:

• proprioreceptors: muscles and joints; physical activity
• baroreceptors: aorta and heart arteries; blood pressure
• chemoreceptors: aorta, heart arteries and medulla; gasses and pH
• emotion centers in brain

stroke volume: volume blood ejected from ventricles

→ typically, 60-80% of blood in ventris is ejected

factors that affect stroke volume:

• preload- amount of tension in ventri muscle BEFORE it contracts; more blood means more stretch
• contractility- force with which ventricular ejection occurs; stronger muscle means more forceful contraction
• afterload- forces the in the arteries the ventricles must work AGAINST in order to eject (i.e. the resistance); increase in afterload/ high bp means decreased stroke volume

vascular system

functions:

• transport nutrients and oxygen
• remove waste

type of blood vessels:

• arteries- carry blood away from heart; usually oxygenated

  → have more smooth muscle fibers

  → strong resist pressure of the ejected blood (thicker muscle layer)

• capillaries- connect smallest arteries to the smallest veins; nutrients and gas exchange occurs here

  → only has the inner layer to allow for diffusion and filtration

• veins- return blood to the heart; usually deoxy

  → have valves inside

layers of blood vessels

• tunica interna- inner; squamous epithelium that is smooth for easy blood flow
• tunica media- middle; smooth muscle and elastic tissue for contraction (dilation/constriction)
• tunica externa- outer; strong connective tissue for support and protection

arteries:

• conducting arteries- large and elastic; receive large volumes of blood, close to the heart
• distributing arteries- muscular arteries; carry blood farther in body to organs
• arterioles- smallest artery; controls blood entering organs and blood pressure

aorta- where all arteries arise (leaves left ventricle)

three regions/branches of aorta:

• ascending aorta- supply the heart

• aortic arch- supply the head, neck and arms

• descending aorta-

  → thoracic aorta before diaphragm- supply thoracic cavity

  → abdominal aorta after diaphragm- supply the abdomen and lower extremities

arteries of the head and brain

• vertebral arteries
• carotid arteries
• circle of willis- arteries that supplies the brain

veins: thinner walls than arteries; stretchy; have valves to prevent backflow

• large veins- formed by veins coming together; close to heart
• medium sized veins- elastic; move blood closer to heart
• venules- smallest veins; collect blood from capillaries

principal veins: superior and inferior vena cava

veins of the head:

• jugular vein
• vertebral vein

hepatic portal circulation- veins from digestive system do not directly drain to the vena cava; they drain to the liver instead; allows liver to remove items ingested before returning to the heart (e.g. glucose, toxins)

→ this can be influnced by hormones

capillaries- link between arterioles to venules; exchange vessels; have extremely thin walls and small diameters which allows for diffusion and filtration

→ tissue w a high metabolic rate have large capillary beds. some tissues don’t have any capillaries (e.g. epithelial)

capillary beds- capillaries are organized into this with arterioles on one side and venules on the other

when tissues at work: precapillary sphincters open; blood flows into the capillary beds for nutrient/waste exchange

when tissues at rest: precapillary sphincters close; blood bypasses capillary beds and flows directly into venules to return to heart

two way exhchange includes: diffusion, osmosis and filtration

arterial end of capillaries

• diffusion (concentration)- allows oxygen to move from blood to tissues
• filtration (pressure)- allows plasma and dissolve nutrients to enter tissues

venules end of capillaries

• diffusion (conc)- allows co2 to move from tissues to blood
• osmosis→ colloid osmotic pressure: allows tissue fluid and waste into capillaries

colloid osmotic pressure:

→ large proteins, like albumin, cannot pass from the capillaries into the tissue with the rest of the plasma

→because fluid (the solvent) exited in the arteriole end, albumin (solute) conc becomes high in the venous end; fluid therefore moves back because of osmosis.

circulation: needed to deliver oxygen, nutrients and remove toxins

→ possible because of pressure gradients (bp) and venous return mechanisms

two circulatory routes are: pulmonary and systemic

pulmonary circulation: used to exchange oxygen and co2 in lungs

→ blood leaved from right ventri

→ travels to lungs

→ oxygen and co2 exchange by diffusion in blood capillaries/ alveoli

→ oxygenated blood returned to left atrium

systemic circulation: used to supply oxygen and nutrients to organs and removes waste

→oxygenated blood leaves from left ventricle (aorta)

→ travels throughout body

→ gas and nutrient exchange occurs in capillaries

→ deoxy blood returned to right atrium (inferior/superior vena cava)

coronary circulation: special type of systemic circulation

→ coronary arteries- supply oxygen to heart; blockage can be deadly (heart attack)

→ coronary veins- collect deoxy blood; empties/returns into right atrium

blood pressure- force exerted by blood against a vessel wall

→ measured as systolic pressure over diastolic pressure (e.g. 110/70)

→blood flow depends on bp; blood flows from high pressure to low pressure- the greater the difference, the faster the flow

factors that affects bp:

→high cardiac output→high bp

→high blood volume→high bp

→high resistance→high bp & low flow

resistance to flow results from friction of blood against walls of vessels

amount of friction depends upon:

→blood viscosity

→vessel diameter

blood viscosity: thickness of blood

→greater viscosity→slower flow

resistance

vessel diameter:

→body’s main control over resistance

→muscles in arterioles can constrict or dilate to change the diameter

→ vasodilation→lower resistance

→vasoconstriction→higher resistance

• greater resistance = greater bp = slower blood flow
• less space = more pressure

regulation of blood flow and pressure

• autoregulation (via blood vessels):

→ tissues need more blood →vasodilation →high flow

→less blood required→vasoconstriction→low flow

• neural regulation (via the medulla oblongata)

→high bp→parasympathetic impulses→vasodilation→low bp

→low bp→sympathetic impulses→vasoconstriction→high bp

regulation of blood flow and pressure

• hormone regulation (via endocrine glands)

→ aldosterone → high bp

→antidiuretic hormone (adh)→high bp

→epinephrine and norepinerphrine → high bp

blood flow through veins

• blood flows due to pressure gradients
• blood flow back to the heart is helped by skeletal muscle pump and respiratory pump

skeletal muscle pump

→ when muscle contract around veins : this moves blood towards heart

→ when muscles relax : valves prevent blood going backwards

respiratory pump

• during inhalation : pressure in the chest cavity drops compared to pressure in the abdominal cavity

→why? because breathing in creates more space in chest

• blood flows from high to low pressure, so it flows from abdomen towards heart in the chest