Animal Histology

Where do granular WBCs come from? Granulopoiesis – formation of granular leukocytes (WBCs) This process occurs in bone marrow along side erythropoiesis with each type (eosinophil, basophil, neutrophil) going through its own pathway. Two processes take place simultaneously: (1) nuclei condense to adult form (bi-lobed, multi-lobed, etc) and (2) the cell begins to synthesize and collect its specific granule population. I. Start with CFU-S WBC 1. Begin with: promyelocyte (big committed stem cell which commits right away to become either a neutrophilic myelocyte, basophilic myelocyte, or eosinophile myeocyte) a.Myelocytes have a begun nuclear changes, possessing a round nucleus or one that is flatten on one side. The cytoplasm shows a minimum of specific granules (eosinophilic or basophilic or azurophilic) 2. Metamyelocyte (MM) b. Metamyelocytes have begun nuclear indentation (horseshoe shaped to mature morphology) and an increase in specific granules 3. Stab Cells ***EXCLUSIVE ONL Y TO NEUTROPHILS*** c. Stab Cells or Band Metamyelocytes are unique to the neutrophil lineage. These cells, approximately the size of mature PMNs have a deep horseshoe or ring-like morphology to their nuclei . Adult Cells final nuclear morphology + specific granules – occur in bone marrow next to developing RBC II. Back in Circulation, last type of WBC: Agranular WBC A. Monocyte a. 2-8% WBC b. LANDMARK: largest circulating WBC 15-20 micron dm (3-4X RBC) c. Nucleus: irregular shaped or horseshoe shape BUT UNLIKE STAB CELLS monocytes are seen in circulation while stab cells are found only in bone marrow d. Precursor to LCT macrophages B. Lymphocyte e. 2nd most common WBC (after neutrophils) 30% WBC f. Dm: 8-10 micron (about a RBC) g.Nucleus fills cell, leaving a royal blue rim of cytoplasm h. Fxn: produce antibodies, secretory cell, has lost of rER, lots of ribosomes, therefore basophilic staining Components of the Circulatory System The circulatory system includes both the blo od vascular system and the lymph vascular system. The blood vascular system includes the heart, arteries, arterioles, capillaries, venules, and veins. A. Intro to the System a. Pump = heart; in reality 2 pumps sitting side by side: (1) the pulmonary circuit and (2) the systematic circuit i. ight half of the heart pumps blood into the pulmonary circuit via the pulmonary artery to the lungs and back to the heart via the pulmonary vein ii. left half of heart then pumps the oxygenated blood into the systematic circuit via the Aorta. In the systemic capillaries oxygen and nutrients leave the blood and waste materials (i. e. CO2) picked up and returned to the heart b. Arteries iii. Decrease in size to arterioles iv. Strong-walled tubes and are distribution system; decide who gets how much c. Arterioles terminate in capillaries v.Capillaries are organized in beds vi. Site of exchange between blood and tissue d. Return to heart via venules, then small veins, then veins, and finally the hear t vii. Pulmonary vein enters left heart, vena cava comes to right I. Arteries In general, three types of arteries are found in the body: (1) Elastic Arteries, (2) Muscular Arteries, and (3) Arterioles. All three types are composed of three coats or tunics: (1) tunica intima (inner most), (2) tunica media (middle), and (3) adventitia (outer most). A. Muscular Arteries a. Most common type of artery . Distributing system: where to send blood and controls Blood Pressure (use muscular layer to control lumen size) c. Composition: i. tunica intima: composed of an inner endothelial lining sitting on an elastic lamina ii. tunica media: the thickest layer, is composed of spiral smooth muscle cells held together by elastic fibers and an encircling elastic lamina iii. tunica adventitia: composed of fibroelastic connective tissue, with much of its elastic component contributing to the make up of the elastic lamina surrounding the media. 1.This layer can be as thick as to 2/3 of that of the media 2. Collagen plus biggest ccn of elastin in muscular arteries, gives recoil ability B. Elastic Artery d. Exit vessels of the heart (pulmonary artery and aorta) e. Gives diastolic number of BP f. Composition: iv. Intima: much thicker (20%) due to increased elastin v. Media: MAJOR DIFFERENCE increased amount of elastic fibers arranged in concentric laminae plus some smooth muscle vi. Adventitia: similar to the muscular artery, except being much thinner, less elastin and more collagen to restrict overexpansion C.Arteriole g. Pressure reducers, don’t want blood to come surging into capillaries h. Composition: contain the same three tunicas, but each is greatly reduced. The intima consist of an endothelium on a basement lamina; the media contains only three layers of smooth muscle cells; and the adventitia thin II. Capillaries in the Body Capillaries are the thinnest walled of all the blood vessels and represent the site of gas and nutrient exchange in the systemic circulatory sys tem. A capillary is composed of endothelial cells, surrounded by a basement membrane A. Continuous Cap (Rare) . Part of any time of blood barrier b. At places you don’t want leaks ex brain c. Sealed with zonula occludens (tight jxns) B. Fenestrated Cap (Most common) d. Riddled with pores to allow exchange e. Produces transudate- maintains osmotic homeostasis (composed of water and ions) f. Exudate: what you make when not normal (water, ions, proteins, cells) Note: Exudate = water + ions + proteins + cells = infections III. Venus System (Return to the heart System) A. Venules a. Capillaries plus extra layers of pericytes b. Collecting venule wrapped in CT (T. dventia) c. Pericytes turn to smooth muscle (T. media) B. Veins d. T. intimia: no elastin lamina thus NO RIBBON CANDY e. T media: thin layer of muscle f. T adventia: thickest layer g. Veins carry bad oxygen poor blood, the media and adventitia cells are supplied with a separate vascular system. These vessels are called th e vaso vasorum and are also found in the walls of large arteries (in T. adventia/T media) h. Veins have valves to prevent blood from backflowing i. Leaflet valves- infolding of the tunica intima ii. Abnormal: varicose veins