Where would one find the most deoxygenated blood?

The liver primarily serves to help detoxify both endogenous and exogenous substances from the blood and intestines. Once blood from the intestines (delivered by the portal vein) or from the systemic circulation (delivered by the hepatic artery) enters the liver, it is filtered over liver cells called hepatocytes. Endogenous substances, such as bilirubin, and exogenous substances, such as drugs, are taken up by transporters on hepatocytes and undergo three phases of metabolism. The three phases allow the transported compound to be detoxified by a method of electron transfer (phase I), by addition of amino acid derivatives (phase II), and finally by exocytosis from the hepatocyte into the bile (phase III). The bile is then transported into the small intestine, and finally excreted from the body.

Amino acid derivatives are often taken from the Krebs cycle, added to sugar nucleotides, and transferred to molecules for detoxification. A common example of an enzyme responsible for this is UDP-glucuronosyl transferase.

The flow of substances through the liver follows the portal triad. The portal triad does not include which of the following structures?

Nutrients absorbed in the small intestine follow which of the following pathways before entering the tissues of the body?

Hemoglobin is the principal oxygen-carrying protein in humans. It exists within erythrocytes, and binds up to four diatomic oxygen molecules simultaneously. Hemoglobin functions to maximize oxygen delivery to tissues, while simultaneously maximizing oxygen absorption in the lungs. Hemoglobin thus has a fundamentally contradictory set of goals. It must at once be opitimized to absorb oxygen, and to offload oxygen. Natural selection has overcome this apparent contradiction by making hemoglobin exquisitely sensitive to conditions in its microenvironment.

One way in which hemoglobin accomplishes its goals is through the phenomenon of cooperativity. Cooperativity refers to the ability of hemoglobin to change its oxygen binding behavior as a function of how many other oxygen atoms are bound to the molecule.

Fetal hemoglobin shows a similar pattern of cooperativity, but has unique binding characteristics relative to adult hemoglobin. Fetal hemoglobin reaches higher saturation at lower oxygen partial pressure.

Because of cooperativity, adult and fetal oxygen-hemoglobin dissociation curves appear as follows.

Beyond its ability to carry oxygen, hemoglobin is also effective as a blood buffer. The general reaction for the blood buffer system of hemoglobin is given below.

H+ + HbO2 ←→ H+Hb + O2

The hemoglobin gene can be the site of catastrophic genetic changes, one of which is the change seen in sickle cell anemia. In this disorder, hemoglobin mutations cause red blood cells to take on a sickled appearance. These cells are less able to flow freely in the blood through tight spaces. Which of the following vessels is most likely to be the site of accumulation of these misshapen cells?

Which of the following incorrectly matches the type of blood with the vessel or structure carrying it?

Which of the following vessels has the highest concentration of oxygen?

Edema is a condition caused by a build-up of fluid in the interstitium.

Which of the following is associated with edema?

Hemoglobin is the protein responsible for the transport of oxygen throughout the bloodstream. The saturation of hemoglobin can be graphed based on the pressure of oxygen. As the pressure of oxygen increases, the saturation of hemoglobin with oxygen will increase in a sigmoidal fashion. This oxygen dissociation curve can be shifted depending on the external conditions in the blood.

Where would hemoglobin have the lowest saturation percentage of oxygen?

What characteristics of arteries and veins allow the heart to pump blood strong enough to travel through the body against gravity without backing up?

In extremely cold temperatures, which of the following is most directly responsible for constricting blood flow to the skin in order to preserve heat?