Vein limbs. The Thebesian veins within the myocardium of the heart are valveless veins that drain directly into the chambers of the heart. The coronary veins all empty into the coronary sinus which empties into the right atrium. The dural venous sinuses within the dura mater surrounding the brain receive blood from the brain and also are a point of entry of cerebrospinal fluid from arachnoid villi absorption. Blood eventually enters the internal jugular vein. "Phlebology" is the medical specialty devoted to the diagnosis and treatment of venous disorders. A medical specialist in phlebology is termed a phlebologist. A related image
Blood–brain barrier was observed between adult and newborn rabbits. These experiments indicate that the newborn BBB has restrictive properties similar to that of the adult. In contrast to suggestions of an immature barrier in young animals, these studies indicate that a sophisticated, selective BBB is operative at birth. The blood–brain barrier acts effectively to protect the brain from circulating pathogens. Accordingly, blood-borne infections of the brain are rare. Infections of the brain that do occur are often difficult to treat. Antibodies are too large to cross the blood–brain barrier, and only certain antibiotics are able to pass. In some cases, a drug