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Circulatory System: Arteries, Capillaries, Venules, and Lymphatics, Slides of Acting

An in-depth exploration of the functions of the circulatory system, focusing on the roles of arteries, arterioles, capillaries, venules, and the lymphatic system. Learn about their structures, functions, and the relationships between vessel diameter, cross-sectional area, blood pressure, and blood velocity. Discover the importance of capillary exchange in homeostasis and the processes of diffusion, filtration, and reabsorption.

What you will learn

  • What causes edema and how is it treated?
  • How does the structure of capillaries facilitate exchange between the blood and tissues?
  • What are the Starling forces and how do they determine fluid movement across capillary membranes?
  • What is the role of the lymphatic system in the circulatory system?
  • What are the functions of arteries, arterioles, capillaries, and venules in the circulatory system?

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2021/2022

Uploaded on 09/27/2022

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Functions of the circulation
To serve the needs of the tissues:
1- Transport nutrients & remove waste products.
2- Transport hormones, enzymes, body heat,
electrolytes ---etc.
3- Maintain normal homeostasis for optimal
survival &function of cells.
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Download Circulatory System: Arteries, Capillaries, Venules, and Lymphatics and more Slides Acting in PDF only on Docsity!

Functions of the circulation

To serve the needs of the tissues:

1- Transport nutrients & remove waste products.

2- Transport hormones, enzymes, body heat, electrolytes ---etc.

3- Maintain normal homeostasis for optimal survival &function of cells.

Functional Parts of the circulation

1- Arteries: Has strong muscular walls. Transport blood Rapidly under high pressure to the tissues.

2- Arterioles: Has strong muscular walls that can close the arteriole completely or dilate it several folds i.e. they alter blood flow to the capillaries in Response to needs.

Arterioles & small arteries are called (Resistance vessels).

4- Venules & Veins:

(Capacitance Vessels)

At rest more than ⅔rds. of total blood

volume is found within the venous system.

More than half of it is within venules.

Structure of the Microcirculation

Smooth muscle Arteriole

Venule

Metarteriole

Capillary

Endothelial cells

Precapillary sphincters

The Organization of a Capillary Bed. (a) A typical capillary bed. Solid arrows indicate consistent blood flow; dashed arrows indicate variable or pulsating blood flow. (b) A micrograph of a number of capillary beds.

Capillary pressures and capillary exchange

Capillary exchange plays important role in

homeostasis.

The important processes that move

Materials across capillary walls are:

1- Diffusion

2- Filtration

3- Reabsorption

Capillary Filtration. Capillary hydrostatic pressure (CHP) forces water and solutes through the gaps between adjacent endothelial cells in continuous capillaries. The sizes of solutes that move across the capillary wall are determined primarily by the dimensions of the gaps.

Graphic Representation of Capillary Filtration

Four Forces known as Starling Forces Determine Fluid Movement Across the Capillary Membranes.

Pc = Capillary Pressure Tends to move fluid out of the capillary

Pi = Interstitial Fluid Pressure Tends to move fluid into the capillary.

Π c = Plasma Colloid Osmotic Pressure Tends to cause Osmosis of fluid into capillary.

Π i = Interstitial fluid colloid osmotic pressure Tends to cause osmosis of fluid out of the capillary.

Net Filtration Pressure = Pnet= ((Pc-Pi) ( Π c- Π i))

Forces Acting across Capillary Walls. At the arterial end of the capillary, capillary hydrostatic pressure (CHP) is greater than blood colloid osmotic pressure (BCOP), so fluid moves out of the capillary (filtration). Near the venule, CHP is lower than BCOP, so fluid moves into the capillary (reabsorption). In this model, interstitial fluid colloid osmotic pressure (ICOP) and interstitial fluid hydrostatic pressure (IHP) are assumed to be 0 mmHg and so are not shown.

Lymphatic circulation

• Lymphatic system is responsible for

bringing the interstitial fluid to vascular

compartment.

• Normal 24 hrs lymph flow is 2- 4 L

• Lymphatic capillaries lie in interstitial

fluid close to vascular capillaries ,these

capillaries merge into large lymphatic

vessels & eventually into largest vessel,

thoracic duct which empties into large

veins.