Ch. 21-B blood vessels

Which blood vessel layer contains more smooth muscles and few/none external elastic membrane?

Tunica Media (Arteries and Veins walls)

Which blood vessel layer contains endothelium and internal elastic membrane?

Tunica Intima (Arteries and Veins walls)

Which blood vessel layer contains collagen, elastic fiber, and none/few smooth muscles?

Tunica Externa (Arteries and Veins walls)

With Arteriosclerosis, Calcification causes Calcium deposits in where?

Tunica Media

With Arteriosclerosis, Atherosclerosis causes Lipid deposits where?

Tunica media (plaque in vessel wall)

What is an Aneurysm?

Bulge in a weakened spot of elastic fibers in the arterial wall

• pressure may rupture the vessel→ serious internal bleeding!

What is Arteriosclerosis?

Hardening and thickening of the arterial wall

What are the types of Capillaries?

Continuous, Fenestrated, and Sinusoids

What is Continous Capillary?

Continuous uninterrupted endothelial cells & basal lamina, fitting closely together & surrounds entire tube

What is Fenestrated Capillary?

“Windows or Pores”; within endothelial lining which allows for rapid exchange of fluids, solutes, and peptides

What is Sinusoids Capillary?

Vessel containing gaps between endothelial cells & may not have a basal lamina

• allows large proteins to pass

Where can you find Fenestrated Capillaries?

Choroids Plexus, Endocrine organs, Kidneys, Intestinal tract

Where can you find Sinusoids Capillaries?

in the Liver, Bone Marrow, Spleen, and Pituitary gland

What is Vasoconstriction?

Narrowing of blood vessels

• smooth muscles contract

• decrease the diameter of the vessel

• increases blood pressure

What is Vasodialation?

Widening of blood vessels

• smooth muscles relax

• increases diameter of the vessel

• decreases blood pressure

What are Capillary Beds (Capillary Plexus)?

Networks of interconnected/interwoven capillaries

• serve as primary sites of exchange→ H₂0, CO₂, nutrients, and waste

What are Precapillary Sphcincters?

Smooth muscle cells that control blood flow through capillaries in a Capillary Bed

• opens and closes certain capillaries

What are Thoroughfare Channels?

A direct passageway connections between arterioles and venules in the capillary bed

What is Arteriovenous Anastomes?

a direct connection between arterioles and venules, that bypass the capillary bed

What is Angiogenesis?

the formation of new blood vessels

• stimulated by Vascular Endothelial Growth Factor (VEGF)

Why does Angiogenesis occur?

due to:

• embryonic & fetal development

• response to Hypoxia → low oxygen in tissues

What are the types of veins?

Venules, Medium-sized veins and Large veins

What are Venules?

Very small veins that collect blood from capillaries

• smaller venules→ don’t have Tunica Media

What are Medium-sized veins?

contain all 3 layers

• have a thin Tunica Media

• Tunica Externa→ contains longitudinal bundles of Collagen & Elastic fibers

What are Large veins?

contains all 3 layers

• have a thick Tunica Externa

• Tunica Media is thinner than corresponding arteries

What is the percentage of blood volume from the Heart, Arteries and Capillaries?

30-35% of blood volume

What is the percentage of blood volume from the Veins and Venules?

65-70% of blood volume

What is Total Peripheral Resistance?

resistance of the entire cardiovascular system

What are some factors that affect the Total Peripheral Resistance?

• Vascular Resistance (R): R α 1/r⁴

  • due to friction between blood & vessel walls

  • depends on vessel length & vessel diameter (2)

• Blood viscosity

  • 4-5x more viscous than water

• Turbulence

  • swirling action that disturbs smooth flow

  • within heart chambers & large vessels

  • “Bruit-sound” → turbulent blood flow thanks to plaque

What occurs if the blood vessel length is long?

greater surface area → more resistance → less blood flow

What occurs if a blood vessel has a short length?

less surface area → less resistance → more blood flow

What occurs if the blood vessel diameter is small?

more friction → more resistance → less blood flow

What occurs if the blood vessel diameter is larger?

less friction → less resistance → more blood flow

WHat is the Capillary pressure (in arterioles)?

35 mmHg

What is the Venous pressure in Venules?

18 mmHg

What is the Venous pressure in Vena Cava?

2 mmHg

What is Mean Arterial Pressure (MAP)?

the average blood pressure in a person’s arteries during 1 cardiac cycle

• normal MAP → 90 mmHg

Within the Arteriole end heading to a Venule, what is the relationship between Capillary Hydrostatic Pressure (CHP) and Blood Colloid Osmotic Pressure (BCOP)?

CHP > BCOP

• Forces pushing blood away is stronger

• Net filtration: 24 L/day

In the middle of a Arteriole and Venule, what is the relationship between Capillary Hydrostatic Pressure (CHP) and Blood Colloid Osmotic Pressure (BCOP)?

CHP = BCOP

• no net movement occurs here

• fluid moves in and out at exact same rate

At the Venule end, what is the relationship between Capillary Hydrostatic Pressure (CHP) and Blood Colloid Osmotic Pressure (BCOP)?

CHP < BCOP

• pulling force is greater than pushing

• reabsorbs→ 20.4 L/day

What causes Capillary Hydrostatic Pressure (CHP)?

caused by blood pressure

• heart pumps → pressure is created

• pushing blood against narrow walls

• pushing blood outwards through tiny gaps in capillary walls

What causes Blood Colloid Osmotic Pressure (BCOP)?

caused by plasma proteins

• liver produces proteins, circulate in the blood

• too large to escape tiny gaps → remain trapped in bloodstream

• proteins then act like a sponge → pulls water back

What is Hydrostatic pressure (HP) in a blood vessel?

physical force that forces water out of a blood vessel solution → Filtration

What is Osmotic Pressure (OP) in a blood vessel?

physical force that forces water into a blood vessel solution → Reabsorption

In Homeostasis, what is Autoregulation?

an immediate, localized homeostatic adjustment to blood flow in specific tissues and organs

In Homeostasis, what is Neural Regulation?

a central regulation, involving a rapid short-term adjustment in CO & peripheral resistance

In Hemostasis, what is Endocrine Regulation?

central regulation by hormones, enhances short-term adjustments and directs long-term changes

What is Local Vasoconstrictors?

can reduce blood flow by closing precapillary sphincters

• ex. Endothelins → released by damaged Endothelial cells

• ex. Prostaglandins & Thromboxanes → released by activated platelets & WBCs

What is Local Vasodilators?

can increase blood flow by opening precapillary sphincters

• ex. low oxygen & high CO2 in tissues

• ex. Nitric Oxide (NO) released by Endothelial cells

• ex. Elevated body temperature

What are Baroreceptor reflexes responsible for?

responsible in responding to changes in blood pressure

What are Chemoreceptor reflexes responsible for?

responsible in responding to changes in chemical composition; pH, O2, and CO2 levels

Where are Baroreceptors located?

stretch receptors in Carotid Sinuses, Aortic Arch, and in Right Atrium

What happens in Baroreceptor reflexes when blood pressure is above normal?

Parasympathetic stimulation & Sympathetic inhibition causes:

• decrease in CO

• peripheral vasodilation

What happens in Baroreceptor reflexes when blood pressure is below normal?

Sympathetic stimulation & Parasympathetic inhibition causes:

• increase in CO

• peripheral vasoconstriction

Where are Peripheral Chemorecptors located?

in Carotid bodies & Aortic bodies

• monitor → pH, CO2 & O2 levels

Where are Central Chemoreceptors located?

Medulla oblongata

• monitors → CO2 levels of Cerebrospinal fluid

Within Endocrine regulation, what does Antidiuretic Hormone (ADH) do?

Elevates BP → reduces water loss at kidneys

• causes Vasoconstriction

When is Angiotensin II released?

when Renal blood pressure is decreased

What does Angiotensin II stimulate?

• Aldosterone production

• ADH secretion

• Increased thirst

• Increased CO & Vasoconstriction

When is Erythropoietin (EPO) released?

released by Kidneys:

• when low BP or O2 content in the blood

• stimulates Peripheral Vasoconstriction

• RBC production in bone marrow

When is Natriuretic Peptides released?

• Atrial NP → prod by cells in R. Atrium

• Brain NP → prod by ventricular muscle cells

released in response→ excessive diastolic stretching (high BP)

What occurs during Light Exercise?

• extensive vasodilation→ in skeletal & cardiac muscle

• local vasodilation→ in skin due to rising body temp.

• Venous return increases w/ muscle contractions & faster breathing

What occurs during Heavy exercise?

• increases the sympathetic activity

• CO increased to MAXIMUM (4x higher than resting CO)

• blood supply to brain is unaffected

• Vasomotor centers→ increase blood flow to skeletal muscles

  • restrict blood flow to non essential organs (digestive system)