Download Lecture 13: Capillary Exchange

Lecture 13: Capillary Exchange
Reading: OpenStax A&P Text Chapter 20
Capillaries
1. Your body has 50,000 miles of capillaries with a surface area equal to 2 football fields. Every cell must be within 0.1mm of a
capillary!
2. Capillaries vary in their leakiness. Leaky capillaries are called “fenestrated.”
A. For example, capillaries in the brain are not very leaky at all (and are one layer of the blood brain barrier), while capillaries
in the glomerulus (kidney) are extremely leaky.
B. The liver, spleen, and bone marrow have special capillaries called sinusoids. These have a much larger diameter than
regular capillaries. This is related to function:
i. The liver produces plasma proteins, as well as filters ALL nutrient rich blood from the digestive system. The sinusoids
allow easy exchange between the liver cells and the blood stream.
ii. In the bone marrow, entire blood cells are born and must enter the circulatory system. Leakier blood vessels are
required to facilitate this function.
iii. The spleen removes old erythrocytes from the blood stream. It also is infested with immune cells (mostly macrophages)
who monitor the blood for invaders.
Hydrostatic pressure
Osmotic pressure
Edema
Capillary exchange
1. Diffusion of stuff down concentration gradients…
2. Bulk flow of fluid in and out of the capillaries due to pressure gradients:
A. Hydrostatic (the push of fluid thru cap pores due to the beating heart)
B. Osmotic (the pull of fluid back in b/c of plasma proteins!)
i. Hydrostatic decreases due to friction
ii. # of plasma proteins stays the same, so osmotic pressure does not change
C. Filtration: net flow of fluid out of plasma into interstitial fluid
D. Absorption: net flow into the plasma from the interstitial fluid
E. Different junctions can determine leakiness…more leaky = more filtration
F. Ultimately, more fluid flows OUT than IN…About 3L filtered every day…Excess fluid is deposited into the Lymphatic
System
3. Transcytosis
Lymphatic System
1. Fluid is pumped around super-leaky vessels and deposited back into the circulation (under the collar bones)
2. Edema(swelling due to gathering of fluid in the interstitial space) occurs when there is a problem with exchange between
circulatory system and lymphatic system. Can occur if:
A. Lymph is not draining correctly due to problems in the lymph nodes
B. Filtration exceeds absorption in the capillaries…
i. EX: Inflammation --> leaky capillary walls --> fluid is pushed out easier
EX: If starving (low protein in blood) fluid pours out of system (ascites, or \kwä-shē-ȯr’-kər)
Biol 7: Human Physiology Spring 16
89
CC-BY Wendy Riggs
Lab 13: Integration Project WORK DAY
Today you get to work on your integration project. Do what you gotta do...
Biol 7: Human Physiology Spring 16
90
CC-BY Wendy Riggs
Ext Brain 13: Capillary Exchange
STUDY GUIDE QUESTIONS:
1. Understand the 3 methods by which exchange of nutrients and wastes occurs in the capillaries.
2. Be able to describe the anatomical differences between the various blood vessels in the body and relate these structural
differences to their functional differences.
3. Define systolic and diastolic.
4. Be able to calculate Mean Arterial Pressure and pulse pressure.
5. Be able to describe each step involved in taking a person’s blood pressure. Understand exactly what is happening in each
stage.
6. Be able to explain the relationship between hydrostatic and osmotic pressure in the capillaries.
7. Define “filtration” vs. “abosorption” and know whether net filtration or absorption occurs in the capillaries every day.
8. What is the purpose of the lymphatic system?
9. What is edema?
10.Describe the structures of different capillaries, and link structure to funciton.
11. Explain the anatomical structures that contain sinusoids and connect sinusoid structure to function.
12.Be able to describe the anatomical differences between the various blood vessels in the body and relate these structural
differences to their functional differences.
13.Define systolic and diastolic.
14.Be able to calculate Mean Arterial Pressure and pulse pressure.
15.Be able to describe each step involved in taking a person’s blood pressure. Understand exactly what is happening in each
stage.
Biol 7: Human Physiology Spring 16
91
CC-BY Wendy Riggs