Special Circulations  Pulmonary Circulation  Hepatic Portal Circulation  Arterial Supply of the Brain and the Circle of Willis  Fetal Circulation

Pulmonary Circulation

CO 2  inferior vena cava  right atrium  tricuspid valve  right ventricle  pulmonary semilunar valve  pulmonary artery  pulmonary capillaries  alveoli

O 2  alveolus  pulmonary capillaries  pulmonary veins  left atrium  left ventricle  aorta  systemic arteries  arterioles  systemic capillaries  venules  veins  vena cava  right atrium

Pulmonary veins carry oxygen rich blood to the heart. Pulmonary arteries carry carbon dioxide rich blood to the lung

Hepatic Portal Circulation  Blood in the veins of hepatic portal circulation comes from draining  Digestive tract organs (stomach, large intestines and small intestines), spleen and pancreas  Hepatic portal vein carries this blood to the liver before it enters the systemic circulation.

Blood goes to liver before entering the systemic circulation  As blood goes through the liver, some of the nutrients are stored or processed in various ways for release into general circulation. Liver helps maintain proper glucose, fat, and protein concentrations in blood

Hepatic Portal Circulation Figure 11.17

 Major vessels of hepatic portal circulation  Splenic vein  drains the spleen, pancreas, stomach and large intestine (via the inferior mesenteric vein)  Superior mesenteric veins  drains the small intestine and the proximal colon  Left gastric vein  drains the lesser curvature of the stomach, empties directly into the hepatic portal vein Hepatic Portal Circulation

Figure 11.16

Hepatic Portal Circulation Figure (drains the small intestine ) The drop of blood would move from the small intestine into the superior mesenteric vein, through the hepatic portal vein, to the liver, then hepatic veins, into the inferior vena cava and then into the right atrium.

Circle of Willis Branches of the internal carotid and vertebral arteries cooperate to form a ring of blood vessels encircling the pituitary gland, at the base of the brain. It is a protective device that provides an alternate set of pathways for blood to reach the brain tissue in case of impaired blood flow anywhere in the system

 Internal carotid arteries divide into Anterior cerebral arteries and middle cerebral arteries  These arteries supply most of the cerebrum

Vertebral arteries join once within the skull to form the basilar artery Basilar artery serves the brain stem and cerebellum

 Posterior cerebral arteries form from the division of the basilar artery  These arteries supply the posterior cerebrum

Arterial Supply of the Brain Figure Aorta  2 subclavian arteries Pathway from heart to occipital lobe of brain

Figure 11.15

Carry CO 2 and waste-laden blood from the fetus to the placenta Umbilical artery

Carry O 2 - and nutrient- rich blood from the placenta to the fetus Umbilical vein

Ductus Venosus Allows blood to bypass the liver and carries blood to the right atrium of the heart. Liver Right atrium Placenta

Ductus arteriosus Bypasses the non- functional lungs and connects the pulmonary trunk and the aorta

Formaen ovale Bypasses the non- functional lungs allowing blood from right atrium to move into the left atrium

Placenta Serves as a respiratory/digestive/ excretory organ for the fetus