A&P Exam 2

What are the 3 layers of a vessel?

What are the 3 layers of a vessel?

Tunica interna Tunica media Tunica externa

What does the tunica interna do?

produces secretions

What does the tunica media do?

contract SM for vasomotor control

Where is the tunica Interna?

vessel lumen

Histology of tunica interna

simple squamous

What composes the tunica media?

SM, collagen, elastin

What composes tunica externa of arteries?

collagen and elastin

What composes tunica externa of veins?

elastin and SM

How is SM regulated?

sympathetic neurons which controls vasomotor

What is the bulkiest arterial layer?

tunica media

What is the bulkiest venous layer?

tunica externa

What does the tunica externa do?

anchors vessels to surrounding tissue

What composes the tunica externa in large veins?

elastin

What do large vessels have within the tunica externa?

network of vessels

What is vasa vasorum?

network of vessels within vessels

What do arteries do?

O2 rich blood away from heart

What do veins do?

O2 poor blood to heart

Blood flow pathway

Heart Arteries Arterioles Capillaries Venules Veins Heart

What are the 3 types of arteries?

1. Elastic

2. Muscular

3. Resistance

What happens to artery diameter as it moves away from heart?

decreases

What are elastic arteries also known as?

conducting

What are muscular arteries also known as?

distributing

What do elastic arteries do?

Shock absorbers that fluctuate with BP changes

What do elastic arteries not fluctuate in response to?

vasomotor control

What do elastic arteries prevent?

pressure surges from damaging artery walls

What are examples of elastic arteries?

aorta subclavians common carotids

What is arteriosclerosis?

narrowing of lumen which decreases artery flexibility

What does arteriosclerosis produce?

aneurysms which can hemorrhage

What does arteriosclerosis more likely affect?

smaller vessels with thin walls

What is an aneurysm?

weakened vessel wall

Which arteries are pressure smoothing to promote steady flow?

elastic

Which artery type is most common?

muscular

Which artery type responds to vasomotor control?

muscular

Which artery type are pulse points?

superficial muscular

What are examples of muscular arteries?

radial, brachial, femoral

Rank arteries from largest to smallest

Elastic Muscular Resistance

How many tunic layers do small resistance arteries have?

Very small?

Small = all 3

Very small = only interna and media

What do resistance arteries respond to?

neural, hormonal, paracrine signals

Why can resistance arteries not handle BP surges?

not elastic

What are resistance arteries control points of?

perfusion

What are the 3 types of capillaries?

1. continuous

2. fenestrated

3. sinusoids

What is the function of capillaries?

gas exchange with tissues

What layers are in capillaries?

only tunica interna

What is a network of capillaries known as?

bed

What is microcirculation?

blood flow through capillaries

also microvasculature

What do continuous capillaries diffuse?

water and small molecules

What do sinusoid capillaries diffuse?

large molecules blood cells

Rank capillaries from least to most permeable

Continuous Fenestrated Sinusoids

What type of capillary prevents protein and blood cell loss?

Continuous

What do continuous capillaries have for extra screening and protection?

specialized tight junctions

Where are continuous capillaries found?

muscles, skin, lungs

What do fenestrated capillaries have?

large lumens and pores

What are examples of fenestrated capillaries?

Kidneys = filter blood Intestines = absorb nutrients Endocrine = hormone uptake and release

What are sinusoid capillaries also known as?

discontinous

What are the characteristics of sinusoid capillaries?

large lumens and irregular shape

What is the speed of flow in sinusoid capillaries?

slow

What are examples of sinusoid capillaries?

Marrow Liver Lymph tissue Endocrine organs

Which has lower BP: veins or arteries

veins

What happens to vein diameter as it gets closer to heart?

increase

What happens at postcapillary venules?

WBC exchange

What are the characteristics of postcapillary venules?

small, porous endothelium

What happens when WBC cling to postcapillary lining and move out of tissue?

inflammation

What layers are present in muscular venules?

all 3 layers

Compare wall thickness for veins and arteries

Thinner walls in veins

Compare lumen size in veins and arteries

Larger lumens in veins

Which BV can accommodate larger volumes of blood?

veins

What are veins also known as?

capacitance vessels blood reservoirs

What do veins not have in their tunica media?

SM and elastin

Why do veins have a low chance of bursting?

low BP

How is vein flow assisted?

valves low resistance large lumen

Where are valves very abundant?

limbs because they can counteract gravity

What are venous sinuses?

Drains

Specialized flattened veins without SM

What are the 5 mechanisms of venous return?

1. Skeletal muscle pump

2. Respiratory/thoracic pump

3. Cardiac suction

4. Gravity

5. Valves

How is venous return achieved through the skeletal muscle pump?

Exercises contracts skeletal muscle and pushes flow along

How is venous return achieved through the respiratory/thoracic pump?

Inhalation increases volume and decreases pressure to move blood

How is venous return achieved through cardiac suction?

heartstrings pull AV valves down to create suction and pull blood from IVC/SVC

How is venous return achieved through gravity?

downhill return from upper body

How is venous return achieved through valves?

inward foldings prevent backflow in limbs

What are varicose veins?

superficial veins that bulge and twist in lower limbs

from weak valves and walls

What causes varicose veins?

Heredity Excess weight standing too long strain

What are hemorrhoids?

anal varicose veins

What is anastomoses?

vessel merger

What are the 3 types of anastomoses?

1. Arterial

2. Venous

3. arteriovenous

What are arterial mergers?

alternative routes for arteries to prevent occlusions

Brain heart Abdomen

What are venous mergers?

alternative routes for drainage

What are arteriovenous mergers?

Connect arterioles to venules to bypass capillaries

Fingers toes ears

What is the function of arteriovenous mergers?

thermoregulation

What are portal systems?

specialized routes of flow where blood passes through 2 capillary networks

Kidney Hypothalamus/ant pit

What is perfusion?

blood flow

What is hemodynamics?

principle of flow

What is blood flow based on?

pressure resistance

What is flow?

volume of blood in time (mL/min)

What is perfusion measured in?

flow per tissue mass

mL/g/min

What is total systemic flow equal to?

cardiac output

What is pressure?

force blood exerts on vessel wall

mmHg

How is pressure influenced?

1. compliance (elasticity)

2. flow

Pressure is measured with what?

sphygmomanometer

What is peak arterial BP known as?

Systole Ventricular contraction

What is minimal arterial BP?

Diastole Ventricular relaxation

What happens to pressure when compliance decreases?

increases (indirect)