Circulatory and Respiratory Systems - NCLEX-PN

Monocytes, the largest of all the leukocytes, make up just 2-10% of the average white blood cell count. These white blood cells will mature into macrophages to phagocytose foreign matter.

Macrophages consume bacteria, cancer cells, and cellular debris via phagocytosis. Once these elements are within the cell, the macrophage is able to use lysosomes to break them down and prepare them for release into the blood as waste, which will eventually be excreted.

Platelets are small cell fragments that play an important role in hemostasis, or clot formation. Once activated, platelets release clotting factors that recruit more platelets till a clot is formed and bleeding stops.

Diapedesis, also known as leukocyte extravasation, is the process by which white blood cells move into and out of blood vessels. This process includes four stages: chemoattraction, rolling adhesion, tight adhesion, and endothelial transmigration. This process is integral in the delivery of white blood cells to sites of infection and in their return into the blood stream to mobilize and facilitate the excretion of waste.

Neutrophils, eosinophils, and basophils are all granulocytes, meaning they contain visible granules within their cytoplasms. These granules contains acids and antimicrobial enzymes, and are released at the site of infection. Monocytes and lymphocytes are agranulocytes, meaning they do not contain granules in their cytoplasm but rather destroy foreign proteins by other means, such as phagocytosis and cytotoxicity.

Platelets are derived from megakaryocytes, cells produced in bone marrow, kidney, liver, and spleen, with large, lobed nuclei. Platelets are formed within the cell and then released into plasma. Erythrocytes (mature red blood cells), plasma cells (a type of B cell) and progranulocytes (precursors to neutrophils, basophils, and eosinophils) take no part in the creation of platelets, which are fragments of cells, not whole cells.

The average adult body contains 4.5-6 liters of blood, depending on size and gender. Blood volume (BV) can be calculated by the following formula, given the hematocrit (HC) and plasma volume (PV):

The three main types of proteins in the blood are albumin, globulin, and fibrinogen. Major histocompatibility complex is not a free plasma protein, but rather a class of proteins found on the surface of all nucleated cells (MHC class I) and on the surface of certain immune cells known as antigen-presenting cells (MHC class II). They play an important part in immune function by displaying foreign antigens for communication between leukocytes.

The only anucleate blood cells are erythrocytes, or red blood cells. These cells are created with nuclei, but each daughter cell will then lose its nucleus in order to create more suface area for hemoglobin to bind oxygen and for easier passage through narrow capillaries.

Depolarization is able to travel in a uniform wave through myocardium due to the presence of gap junctions. These junctions allow the depolarizing current to be transmitted directly from cell to cell in the heart. Striation in cardiac muscle is a feature of contraction, created by overlapping thick and thin contractile filaments. Desmosomes are strong fiber-like anchors between myocardial cells, and T-tubules, while an important part of depolarization, are not responsible for the rapid inter-cellular communication that occurs as a result of the presence of gap junctions.

Sympathetic innervation will decrease the heart rate, which will automatically decrease the cardiac output

The vagus nerve provides the main parasympathetic innervation of the heart. The recurrent laryngeal nerve, a branch of the vagus nerve, innervates the majority of the intrinsic muscles of the larynx. The cardiac nerve is part of the sympathetic innervation of the heart.

The majority of blood supply to the left atrium and left ventricle is provided by the left coronary artery. The septal branches and left circumflex artery are smaller divisions of this main artery. The posterior descending artery supplies the posterior one-third of the interventricular septum.

The nurse is most likely palpating the abdominal aorta. This vessel is large, generally 2.5-4 cm in diameter, and a strong pulse can often be felt on palpation. The femoral artery is also an area where a pulse may be felt, but it is only palpable in the mid-inguinal point of the inner thigh. The exterior iliac artery branches off of the abdominal aorta below the umbilicus, and the inferior mesenteric artery is a minor artery and is not generally palpable on examination.

The lymphatic system has several roles in the body, including drainage of interstitial fluid from tissues, transportation and activation of lymphocytes, and absorption and transportation of dietary fats. Red blood cells, however, are unable to enter lymph vessels, and so the lymphatic system does not participate in any type of gas exchange.

T-cell maturation occurs in the thymus, a small organ located in the upper part of the mediastinum, between the heart and the sternum. Mature T cells then may either circulate in the lymph or blood or reside in lymph nodes. The spleen is not a site of T cell maturation, though it does have other important immune functions, such as the production of antibodies and the removal of antibody-coated pathogens. The cisterna chyli is a part of the lymphatic system that is involved in lipid digestion.

Dietary fat is absorbed via lacteals, small lymph vessels contained within the body of the intestinal villi. Microvilli, tiny projections covering the surface of the villi, help with the absorption of minerals, vitamins, and other micronutrients. The cisterna chyli is a dilated pouch at the lower end of the thoracic duct that serves as a collection point for fatty chyle from the intestinal lacteals.

There are five lobes total in the human lungs: the right lung has three lobes (the upper lobe, the middle lobe, and the lower lobe) while the left lung has two lobes (the upper lobe and the lower lobe).

The topmost part of the lungs is the apex. This area extends into the neck above the 1st rib and is the location auscultated for a diagnosis of a pancost tumor. The lingula of the lung is a small flap of the lowest part of the upper lobe of the left lung. The hilum is the entry point of the lung for the bronchi, pulmonary artery and vein, and nerves. The trachea is not a part of the lung at all; it is the cartilaginous tube that connects the pharynx and larynx to the lung.

The largest airway structure is the trachea. This branches into two smaller bronchi, which enter the left and right lung and bifurcate further into smaller bronchioles. The bronchioles give way into the smallest structures of the lung, the tiny grape-like clusters of alveoli.