Special Circulations

The lymphatic system is another circulatory network with two main functions:

1. Recovering fluid leaked from capillaries

2. Transporting leukocytes

Vascular anastomoses

merging or branching networks of blood vessels outside of capillary beds

Why are vascular anastomoses important?

They provide redundant “backup” routes for blood flow into important regions like

• Circle of Willis (brain)

• Coronary circulation (heart)

What types of vascular connections exist in anastomoses?

• Arteries-to-arteries

• Veins-to-veins

• Arteries-to-veins

Circle of Willis

vascular anastomosis that supplies blood to the brain

What arteries feed into the Circle of Willis?

• Internal carotid artery

• Vertebral artery

Hepatic portal system

Double capillary system where blood goes from the intestines to the liver before returning to the heart

Why is the hepatic portal system important?

it allow the liver to filter and detoxify blood that absorbed nutrients, toxins, or pathogens from the digestive tract

Where are the double capillary beds in the hepatic portal system?

• One in digestive organs

• One in the liver

What veins feed into the hepatic portal vein?

• Splenic vein

• Inferior mesenteric vein

• Superior mesenteric vein

What is the order of the hepatic portal circulation path?

1. Veins (splenic, inferior mesenteric, superior mesenteric)

2. Hepatic portal vein

3. Liver capillary beds

4. Hepatic veins

5. Inferior vena cava

The fetal circulatory is necessary because it

bypasses the pulmonary circuit since lungs are not functional before birth

The fetal circulatory system also bypasses the

kidneys and liver because placenta handles filtration and detox

What kind of oxygenation is fetal blood typically?

• Most fetal blood is low in O2

• Some mixes to become moderate O2

• High O2 blood enters from the placenta via the umbilical vein

What does the umbilical vein do?

Carries high O2 blood from the placenta into the fetal body

What is function of the ductus venosus?

Shunt that allows blood from the umbilical vein to bypass the liver and flow into the inferior vena cava

What is the function of the foramen ovale?

Opening between the right and left atria that allows blood to bypass the lungs

What is the function of the ductus arteriosus?

Shunt from the pulmonary artery to the aorta that bypasses the lungs

What do the umbilical arteries do?

Carry low O2 blood back to the placenta to be oxygenated