Tutorial June 25

Bio 155

Blood

• Cellular component: 1) RBC2) WBC3) Platelet

• Rh Factor

• A woman is at risk when she has a negative Rh factor and her partner has a positive Rh factor. This combination can produce a child who is Rh positive.

• While the mother's and baby's blood systems are separate there are times when the blood from the baby can enter into the mother's system. This can cause the mother to create antibodies against the Rh factor, thus treating an Rh positive baby like an intruder in her body. If this happens the mother is said to be sensitized.

• A sensitized mother's body will make antibodies. These antibodies will then attack an Rh positive baby's blood, causing it to breaking down the red blood cells of the baby and anemia will develop. In severe cases this hemolytic disease can cause illness, brain damage and even death.

Capillary Network:• Blood flows from

arterioles through metarterioles, then through capillary network

• Venules drain network

• Smooth muscle in arterioles, metarterioles, precapillary sphincters regulates blood flow

Capillary Exchange andInterstitial Fluid Volume

Regulation

• 1) Blood pressure, 2) capillary permeability, and 3) osmosis affect movement of fluid from capillaries

• A net movement of fluid occurs from blood into tissues. Fluid gained by tissues is removed by lymphatic system.

Fluid Exchange Across Capillary Walls

CHP vs OP

• Capillaries are where fluids, gasses, nutrients, and wastes are exchanged between the blood and body tissues by diffusion.

• Fluid exchange is controlled by blood pressure within the capillary vessel (hydrostatic pressure)(pumping action of the heart) and osmotic pressure of the blood within the vessel.

• The osmotic pressure is produced by high concentrations of salts and plasma proteins in the blood.

• The capillary walls allow water and small solutes to pass between its pores but does not allow proteins to pass through.

Fluid Exchange Across Capillary Walls

Movement of Fluid In and Out• As blood enters the capillary bed on the arteriole end, the blood pressure

in the capillary vessel (hydrostatic pressure,HP) > the osmotic pressure of the blood in the vessel. The net result is that fluid moves from the vessel to the body tissue ( OUT).

• At the middle of the capillary bed, blood pressure (HP)in the vessel = the osmotic pressure of the blood in the vessel. The net result is that fluid passes equally between the capillary vessel and the body tissue. Gasses, nutrients, and wastes are also exchanged at this point.

• On the venule end of the capillary bed, blood pressure in the vessel(HP) < the osmotic pressure of the blood in the vessel. The net result is that fluid, carbon dioxide and wastes are drawn from the body tissue into the capillary vessel (IN).

Important Facts

• 24 L/Day is being filtered• 20.4 L/Day is being reabsorbed• 3.6 L/Day goes to lymphatic system and is

returned to the venous system

Blockage of a major lymph vessels in leg

• The fluid lost from the capillary will not be able to be returned to the venous system via the lymphatic system.

• Edema (Excess fluid in the tissue)• Increase in size Elephantiasis

protein leaking out of capillary?

• Osmotic pressure decreases• So fluid has less chance of re-entering the

capillary at venule end• Reabsorption rate decreases • Excess fluid in the tissue• Edema

Pressure and Resistance Blood pressure

averages 100 mm Hg in aorta and drops to 0 mm Hg in the right atrium

Greatest drop in pressure occurs in arterioles which regulate blood flow through tissues

No large fluctuations in capillaries and veins

Blood Volume

–Most in the veins–Smaller volumes in arteries and capillaries

Fetal circulation:

Foramen Ovale• a hole between the left and right atria (upper

chambers) of the heart• A foramen ovale allows blood to go around the

lungs. A baby's lungs are not used when it grows in the womb, so the hole does not cause problems in an unborn infant.

• Normally this opening closes at birth. When the lungs become functional at birth, the pulmonary pressure decreases and the left atrial pressure exceeds that of the right. This forces the septum primum against the septum secundum, functionally closing the foramen ovale.

Ductus Arteriosus

• a short broad vessel in the fetus that connects the pulmonary artery with the aorta and conducts most of the blood directly from the right ventricle to the aorta bypassing the lungs.

• If it does not close leads to pulmonary hypertension and possibly congestive heart failure

Ductus Venosus

• the vascular channel joining the umbilical vein with the inferior vena cava.

• it allows oxygenated blood from the placenta to bypass the liver.

• It closes shortly after birth as pulmonary circulation is established and as the vessels in the umbilical cord collapse and become occluded.