CV Anatomy and Physiology

What makes up the thorax?

spine, ribs, sternum

the body of the sternum is…

flexible - for impact like CPR

the thorax changes…

with development!

triangle to square to rectangle as we get older

What are the muscles of inspiration?

diaphragm, external intercostals, accessory muscles

The diaphragm:

MAIN muscle of innervation

innervated by phrenic nerve - C3, 4, 5

brings in about 2/3 of our tidal volume and ¾ of our air intake when supine

External Intercostals:

lift ribs, increase intrathoracic volume

secondary role to maintain space in between ribs

Accessory muscles:

stabilize ribcage - anything JAW to PELVIC FLOOR

contribute to ventilation and breathing in some way

Quiet expiration is a…

a passive process!!

What happens during quiet expiration?

the inspiratory muscles stop contracting

lungs recoil to resting position

ribs return to resting position

diaphragm rises back into thoracic cavity - increases intrathoracic pressure above atmospheric pressure pushing air out

Forced expiration requires:

abdominals, accessory muscles, postural stabilizers

What are the three ventilatory movements?

pump handle motion

bucket handle motion

combination of movements

What are the muscle movements of ventilation?

diaphragm - A-P diameter

intercostals - lateral expansion

accessory muscles - sup/inf expansion

What is paradoxical breathing?

chest falls when breathing in and rises when breathing out - seesaw motion of chest

What is inspiration?

expansion of the chest creates negative intrathoracic pressure in relation to the atmosphere

What is expiration?

positive pressure relative to the atmosphere

How does intrathoracic pressure relative atmospheric pressure

intrathoracic is INVERSE to atmospheric

Our drive to breathe is based on…

our need to get rid of CO2

Central control center of breathing:

medulla, pons, chemoreceptors

control of involuntary respiratory activity

maintains normal patterns of breathing

Peripheral control center of breathing:

chemoreceptors, stretch reflex, cough reflex

these chemoreceptors cue you to breathe!

stretch tells your brain if the respiratory muscles are firing correctly or something didn’t feel right

What is compliance?

flexibility - how stretchy our lungs are

What is restrictive lung disease?

can’t get air IN - non-compliant lungs

What is obstructive lung disease?

can’t get air OUT

What is the pressure/volume relationship of breathing?

pressure goes UP, volume of air goes DOWN

Airway resistance of breathing:

more resistance increases amount of work muscles of respiration have to do to get air into the lungs

more resistance = harder to move air

What is laminar flow?

air flows in straight path - low resistance

What is turbulent flow?

coffee stirrer or little straw

What is diffusion?

moving of oxygen out of the alveoli to the circulation

oxygen crosses alveolar membrane and capillary membrane to reach circulation - CO2 does this in OPPOSITE order

Movement of oxygen depends on…

distance between membranes and the diffusion capacity of the gas itself

What is perfusion?

blood flow

gravity dependent - more air and blood to the bases when upright

What is dead space?

if we have an alveolus that is getting air into the lungs but NOT getting blood flow

pulmonary embolus

What is shunting?

blood supply at that capillary, ready to accept oxygen, but NO AIR getting to the alveolus

Sympathetic NS innervation:

autonomic ganglia

bronchodilation

pulmonary artery constriction - raises PA pressure

decreased glandular secretion - dries airway surface

raises heart rate and contractility

coronary artery DILATION

Parasympathetic NS innervation:

vagus N

bronchoconstriction

dilation of pulmonary artery - lowers pressure

increased glandular secretion

coronary artery CONSTRICTION

decreased HR, decreased contractility

Arteries:

thick walls

elastic

handles blood under pressure

Veins:

thin walls

fibrous

holds large amount of blood

Systemic circulation:

large arteries to small capillaries

start in small venule, increase in size to vena cava

distribution, resistance and capacitance vessels

Pulmonary circulation:

colors are switched!

arteries - deoxygenated blood

veins - oxygenated blood

PA pressure decreases, PV pressure goes UP - vice versa

Lymphatic circulation:

returns fluid from interstitial spaces back into systemic circulation

fluid collected by channels and ducts if not collected by veins

Cardiac cycle events:

systole - blood ejects from the chamber

diastole - we relax, blood fills the chamber

S1 - lub

S2 - dub

S3, S4 - abnormality of filling phase