blood vessels

what do capillaries do

directly contact tissues to serve cellular needs

microscpic vessels

3 layers of blood vessel

tunica intima

tunica media

tunica externa

Tunica intima made of

Simple squamous epithelium

Tunica media made of

Smooth muscle and elastin

Maintains flow+ pressure

Tunica externa made of

dense, irregular CT, mainly dense collagen that protect BV and anchor it to surrounding structures

types of arteries

• elastic- larger diameter

• muscular- medium diameter

• arterioles “resistance arteries” smallest arteries

Anastomoses

Union of branches of 2+ arteries that supply same region of body

Alternate blood flow route

3 types of capillaries

• continuous

• Fenestrated

• Sinusoidal

Continuous capillaries

have small intercellular clefts except in brain

Except in brain – forms blood brain barrier, no intercellular class

Where continuous capillaries are found

Skin, muscles, lungs, CNS

Fenestrated capillaries

• areas of active filtration, absorption, or endocrine hormone
  secretion

• endothelial cells have “swiss cheese” pores

Where fenestrated capillaries are found

kidneys, intestines

Sinusoidal capillaries

• Fenestrated with larger intercellular clefts and incomplete basement membranes

• slower flow for large molecules

Where sinusoidal capillaries are found

liver, red bone marrow, spleen

what are capillary beds

• Network of capillaries b/w arterioles and venules for microcirculation-arteriole to venule through the capillary bed

3 ways of capillary exchange

• diffusion- oxygen, Co2, glucose, amino acids, some hormones

• Transcytosis- Large, lipid-insoluble molecules (insulin)

• Bulk flow- a lot of ions, molecules, or particles in a fluid move together from high to low pressure areas

What gets exchanged via transcytosis

• Large, lipid-insoluble molecules (insulin)

Filtration

pressure-driven movement of fluid and solutes from blood capillaries into interstitial fluid
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Factors that promote filtration

Blood hydrostatic pressure (BHP)

interstitial fluid osmotic pressure (IFOP)

reabsorption

pressure-driven movement of fluid and solutes from interstitial fluid into blood capillaries

Factors that promote reabsorption into capillaries

Interstitial fluid hydrostatic pressure (IFHP) and
blood colloid osmotic pressure (BCOP) promote reabsorption

Hydrostatic pressure

pushes things out of capillaries

Osmotic pressure

Pressure albumin is exerting; Albumin helps keep water in bloodstream

Hydrostatic pressure of interstitial fluid

should be ~0 mm Hg

push fluid into capillaries

Osmotic Pressure of interstitial fluid

~1 mm Hg

pulls substances out of capillaries

Starling’s Law of Capillaries

Under normal conditions, the volume of fluid and solutes reabsorbed is almost as large as the volume filtered

define venules

• Small vessels formed by union of several capillaries

• drain blood from capillaries into veins
  (~20 micrometers)

physical characteristics of veins & venules

• larger lumen than arteries, but looks collapsed

• has valves

• called capacitance vessels

3 factors to benefit venous return

• muscular pump

• respiratory pump

• Sympathetic vasoconstriction

varicose veins

• Veins expand, space b/w valves increases (become leaky or incompetent) and blood goes back down, pooling in one area

• causes twisting of veins

2 factors of blood flow

• bp

• vascular resistance

Define blood flow

The volume of blood flowing through vessel/organ/or entire circulation and given period

What is blood flow equal to?

Equivalent to cardiac output for entire vascular system

define vascular resistance

Opposition to blood flow due to friction b/w blood and BV walls

What part of body contains cardiovascular center?

Medulla oblongata ( for heart rate, contractility, BV diameter)

4 factors that increase blood pressure

1. Epinephrine

2. Norepinephrine

3. Vasoconstriction

4. Increase of blood volume

Define shock

An inadequate cardiac output, resulting in failure of CV system to meet metabolic demands of body cells

hypovolemic shock

results from large-scale blood loss

Vascular shock

results from extreme vasodilation and decreased peripheral resistance

Cardiogenic shock

results when an inefficient heart cannot sustain adequate circulation

pre-hypertension range

120-139 S

80-89 D

stage 2 hypertension range

160+ S

100+ D

Responses to shock

1. Activation of RAA system

2. Secretion of ADH

3. Activation of sympathetic division of ANS

4. Release of local vasodilators

Define baroreceptors

Pressure sensitive sensory neurons that monitor BV wall stretching, and atria stretching

Where the vertebral arteries Pass through to get to brain

vertebral foramen of cervical vertebrae

Define pulse

Traveling pressure wave caused by alternate expansion of elastic arteries after each systole of left ventricle