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Bacteria have a rudimentary immune system in the form of enzymes that protect against viral infections. Other basic immune mechanisms evolved in ancient plants and animals and remain in their modern descendants. These mechanisms include phagocytosis, antimicrobial peptides called defensins, and the complement system.
Substances called vasoconstrictors can reduce the size of blood vessels, thereby increasing blood pressure. Vasodilators (such as nitroglycerin) increase the size of blood vessels, thereby decreasing arterial pressure. If the blood viscosity increases (gets thicker), the result is an increase in arterial pressure.
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. [1] Blood is composed of blood cells suspended in blood plasma.
The blood clot contains the secondary hemostasis plug with blood cells trapped in it. This is a necessary step for wound healing , but it has the ability to cause severe health problems if the thrombus becomes detached from the vessel wall and travels through the circulatory system; If it reaches the brain, heart or lungs it could lead to ...
The blood–brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that regulates the transfer of solutes and chemicals between the circulatory system and the central nervous system, thus protecting the brain from harmful or unwanted substances in the blood. [1]
When there is an injury to a blood vessel, the endothelial cells can release various vasoconstrictor substances, such as endothelin [23] and thromboxane, [24] to induce the constriction of the smooth muscles in the vessel wall. This helps reduce blood flow to the site of injury and limits bleeding.
Contrary to popular belief, haemoglobin is not a blood protein, as it is carried within red blood cells, rather than in the blood serum. Serum albumin accounts for 55% of blood proteins, [ 1 ] is a major contributor to maintaining the oncotic pressure of plasma and assists, as a carrier, in the transport of lipids and steroid hormones .
This is an accepted version of this page This is the latest accepted revision, reviewed on 31 January 2025. List of organ systems in the human body Part of a series of lists about Human anatomy General Features Regions Variations Movements Systems Structures Arteries Bones Eponymous Foramina Glands endocrine exocrine Lymphatic vessels Nerves Organs Systems Veins Muscles Abductors Adductors ...