IPHY 3430 10-25-11. Exchange of materials in capillaries Diffusion Bulk Flow.

IPHY 3430 10-25-11

Exchange of materials in capillaries

DiffusionBulk Flow

Diffusion:

When the blood reaches the capillaries, many nutrients, O2, and metabolic end products diffuse out/in (down concentration gradients) between the blood and cells.

Cellular utilization or production of materials causes diffusion gradient to exist between blood and cells.

Bulk Flow

Plasma (minus most plasma proteins) is moved by bulk flow out of the capillaries, moving all water soluble materials to the cells, and then most of the water is restored back to the circulation, carrying wastes.

Forces: Capillary blood pressure (outward) Plasma colloid osmotic pressure (inward)

beginning end

BP = 37 BP = 17COP = 25 COP = 25

37-25 = 12 out 25-17 = 8 in

Lymph circulation picks up the rest

unabsorbed “water” containing wastes, ions, etc from extracellular fluid spaceloose plasma proteinsloose red blood cellscell debrispathogenscancer cells

Lymph flow caused by:

1. Skeletal muscle contraction2. Smooth muscle contraction in

walls of lymph vessels3. SNS stimulation to walls of lymph

vessels

Excretory System

Roles:remove wastesbalance body water contentbalance body ionic contentbalance acid-base balance

Kidney also regulates RBC’s and secretes renin as part of regulation of blood pressure

Kidney: by regulating blood water, ionic and H+ content, can regulate extracellular fluid and cell water, ionic and H+ content

Extracellular fluid

blood

Water, ions and H+

If blood water drops, increase blood ion content, and withdrawwater from extracellular tissues, and then water would leave cell

Plus,…

1. adrenal gland (aldosterone)2. hypothalamus and posterior

lobe of the pituitary (vasopressin)

3. Heart atrium (atrial natriuretic factor)

Fig. 14-3, p. 504

Glomerular filtration

55- (30 + 15) = 10 mm Hg

blood

Bowman’s Capsule 15

BP = 55 COP = 30

How glomerular filtration can be varied:Increased blood pressure65- (30 + 15) = 20 mm Hg

blood

Bowman’s Capsule 15

BP = 65 COP = 30

How glomerular filtration can be varied:Dehydration55- (35 + 15) = 10 mm Hg

blood

Bowman’s Capsule 15

BP = 55 COP = 35

Materials filtered into Bowman’s capsule

WaterIonsglucose, amino acidswastes (NH3, urea, etc)a few plasma proteinseverything else in plasmahopefully no cells