Cardio system components
- Heart
- Vessels
- Blood
Vessel components
- Arteries
- Capillaries
- Veins
- Lymphatics
Functions
- Blood supply and delivery
- Waste removal
- Communication via endocrine
- Inflammation
- Thermoregulation
Can you tell veins from arteries histologically?
Yes! Arteries have thicker walls due to higher blood pressure and smooth muscle linings
Circulation in most mammals
2 circuits: (interconnected)
- Pulmonary
- Systemic
- Flow in response to pressure gradients*
Heart functions
- Muscular pump (cardiac muscle)
- Autonomic nervous stimulation
ECG
Tells you about degree of polarization/depolarization, not about strength or contractility
3 layers of the cardiac system (heart, veins, arteries)
- Epicardium
- Myocardium
- Endocardium
Epicardium
Serosal (outer) layer
- Simple squamous epithelium with a CT base
Visceral layer: sits against the outer surface of the heart
Parietal layer: attaches to the pleura
Myocardium
Made of cardiac muscle
Endocardium
Thin wall
- -> stops blood from clotting in circulation
- -> when damaged, underlying CT is exposed and activates clotting factors
Valves
- AV
- Pulmonic
- Aortic
Which valve of the heart is bicuspid?
Left AV valve
Arteries
- high pressure! what gives you a pulse*
- –> multiple rings of connective tissue and smooth muscle
- large (elastic): aorta
- medium (muscular): smooth muscle
- Small: arterioles
Aorta
Stretchable and shrinks back to normal size without expending energy
–> maintains bp in larger arteries
What has active control over blood pressure?
Smooth muscle
Artery layers
- Intima: endothelium, simple squamous, prevents clotting
- Media: smooth muscle, CT (loose areolar), elastic
- Adventitia: outer layer CT, holds arteries in place, vasa vasorum
Vasa Vasorum
Found in large arteries
- Blood vessel that nourishes the big vessels
- is microscopic (hard to see histologically)
______ is continuous with connective tissue on the outside of the muscle
Adventitia
Capillaries
Smallest diameter vessels
- only fit 1 RBC at a time (7-10 microns wide)
- O2 and metabolic exchange
Types of capillaries
- Continuous: endothelium, little CT, tight junctions
- Fenestrated: endocrine glands and GIT, absorption (endothelial cells thin out = holey)
- Discontinuous: sinusoidal (liver, spleen, marrow)
Veins/venules
Low pressure
- Same tunics, not as distinct
- Valves
Vein tunics
- Minimal tunica media
- Adventitia usually largest, collagen, elastin
Venules
- Post capillary (leaky)
- Muscular (more media)
