CVS Endocrine Histology PDF

CARDIOVASCULAR SYSTEM AND ENDOCRINE HISTOLOGY HPHS222 Dr Lindokuhle Mabuza ([email protected]) INSPIRING GREATNESS  Cardiovascular System  The cardiovascular system is composed of the following structures:  H...

CARDIOVASCULAR SYSTEM AND ENDOCRINE HISTOLOGY HPHS222 Dr Lindokuhle Mabuza ([email protected]) INSPIRING GREATNESS  Cardiovascular System  The cardiovascular system is composed of the following structures:  Heart - pumps blood through the system  Arteries - vessels that deliver blood to tissues  Capillaries - networks of small vessels that perfuse tissues  Veins - vessels that return blood to the heart  The heart is a muscular organ that functions as a pump. It creates the force that starts the movement of the blood within blood vessels.  The heart wall has three layers:  Endocardium  Myocardium  Epicardium INSPIRING GREATNESS  Wall of The Heart endocardium E, myocardium M, epicardium P, papillary muscles PM INSPIRING GREATNESS  Epicardium fibrocollagenous tissue F, myocardium M INSPIRING GREATNESS  Myocardium capillary network C, intercalated discs ID INSPIRING GREATNESS  Endocardium endothelial cells E, fibrous connective tissue F, cardiac muscle cells M, Purkinje fibres P INSPIRING GREATNESS  Blood Vessels Layers (Tunics)  Blood vessels have walls composed of three layers (or tunics).  Different types of vessels display functional variations in the thickness and composition of these layers.  Walls of both arteries and veins have the same three-layered structure. The whole circulatory system has a common basic structure:  An inner lining, the tunica intima, comprising a single layer of extremely flattened epithelial cells called endothelial cells supported by a basement membrane and delicate collagenous tissue.  An intermediate predominantly muscular layer, the tunica media.  An outer supporting tissue layer called the tunica adventitia. INSPIRING GREATNESS  Blood Vessels Layers (Tunics) Blood vessels - Tunica Intima - Tunica Media - Tunica Adventitia INSPIRING GREATNESS  Comparison of Tunics in Arteries and Veins Tunic (Layer) Arteries Veins  Thick walls with small lumens  Thin walls with large lumens General Appearance  Generally appear rounded  Generally appear flattened  Endothelium usually appears wavy due to constriction of  Endothelium appears smooth Tunica Intima smooth muscle  Internal elastic membrane absent  Internal elastic membrane present in larger vessels  Normally thinner than the tunica externa  Normally the thickest layer in arteries  Smooth muscle cells with elastic and collagen fibers  Smooth muscle cells and elastic fibers predominate (the Tunica Media  Nervi vasorum and vasa vasorum present proportions of these vary with distance from the heart)  External elastic membrane absent  Nervi vasorum and vasa vasorum present  External elastic membrane present in larger vessels  Normally thinner than the tunica media in all but the largest  Normally the thickest layer in veins arteries  Collagen and smooth fibers predominate Tunica Externa  Collagen and elastic fibers  Some smooth muscle fibers  Nervi vasorum and vasa vasorum present  Nervi vasorum and vasa vasorum present INSPIRING GREATNESS  The Arterial System  Distribute blood from the heart to capillary beds throughout the body.  Systole- blood is forced into the arterial system causing expansion of the arterial walls; subsequent recoil of the arterial walls assists in maintenance of arterial blood pressure between ventricular beats (diastole).  The walls of the arterial vessels are characterised by the presence of elastin and the smooth muscle wall is thick relative to the diameter of the lumen.  There are three main types of vessel in the arterial system:  Elastic arteries. These comprise the major distribution vessels and include the aorta and most of the large pulmonary arterial vessels.  Muscular arteries. These are the main distributing branches of the arterial tree  Arterioles. These are the terminal branches of the arterial tree which supply the capillary beds. INSPIRING GREATNESS  The Venous System  A low-pressure component of the blood circulatory system which is responsible for carrying blood from the capillary networks back to the right atrium of the heart.  The force (often against gravity) is a combination of contraction of the smooth muscle of the vein wall and external compression of veins by contraction of skeletal muscles.  Backflow of blood is prevented by valves.  There are four main types of vessel in the venous system:  Pulmonary veins are responsible for carrying oxygen rich blood from the lungs to the heart.  Systemic veins carry deoxygenated blood from the rest of the body back to the heart.  Superficial veins lie near the skin’s surface and lack corresponding arteries,  Deep veins are found within muscle tissue and do have a corresponding artery. INSPIRING GREATNESS  Artery and Vein Muscular artery (top) and Vein (bottom) INSPIRING GREATNESS  Elastic Arteries  Elastic arteries conduct blood from the heart to different areas of the body. These vessels include the aorta, pulmonary artery, and their largest branches.  The tunica media contains many concentric fenestrated sheets of elastin (i.e., elastic laminae) interspersed with smooth muscle cells.  This elastic tissue allows these vessels to distend when the blood pressure rises (systole), and recoil when the blood pressure falls (diastole). This pumping action helps maintain blood pressure through the cardiac cycle. INSPIRING GREATNESS  Elastic artery tunica intima I, tunica media M, tunica adventitia A, vasa vasorum V INSPIRING GREATNESS  Muscular Arteries  Muscular arteries distribute blood to specific organs in response to their functional needs. Most of the named arteries in the body are muscular arteries.  The tunica media is composed of concentric layers of smooth muscle cells. The contraction and relaxation of these muscle cells regulate blood flow by changing the size of the lumen.  A prominent internal elastic lamina separates the tunica intima from the media. In larger arteries, an external elastic lamina also separates the tunica media from the adventitia. INSPIRING GREATNESS  Vasa Vasorum  Nutrients reach the cells of the vascular wall by diffusion from the lumen. In large vessels, small blood vessels (vasa vasorum) in the tunica adventitia supply the outer layers.  These layers vary in thickness depending on the type of vessel (arteries, arterioles, venules, and veins). INSPIRING GREATNESS Endocrine System INSPIRING GREATNESS  Endocrine Glands  Pituitary Gland - situated at the interface between the brain and the rest of the body and secretes numerous hormones affecting many aspects of physiology  Pineal Gland - secretes melatonin which modulates sleep patterns  Thyroid Gland - secretes hormones that primarily influence the metabolic rate, protein synthesis and calcium metabolism  Parathyroid Glands - secretes parathyroid hormone that causes increase Ca 2+ blood levels  Adrenal Glands - secretes a variety of hormones including adrenaline and the steroids aldosterone and cortisol  Pancreatic Islets (or islets of Langerhans) - secrete hormones that regulate glucose and lipid metabolism  Ovary - secrets the steroids estrogen and progesterone that regulate changes in menstrual cycle and during pregnancy  Testis - secretes the steroid testosterone that regulate the development of male characteristics INSPIRING GREATNESS Pituitary Gland INSPIRING GREATNESS  Anterior Pituitary (Adenohypophysis)  Cells are arranged as irregular cords in between thin-walled fenestrated sinusoids.  Consists of 2 major group of cells: chromophils & chromophobes.  Chromophils - stain with H&E and secrete hormones.  Acidophils - stain pinkish-red with H&E.  Somatotrophs - growth hormone (GH).  Mammotrophs (Lactotrophs) - prolactin.  Basophils - stain bluish-purple with H&E.  Corticotrophs - ACTH.  Thyrotrophs - TSH.  Gonadotrophs - FSH and LH.  Chromophobes - stain poorly with H&E and do not secrete hormones.  Sinusoidal Capillaries - extensive network that receives hormones from acidophils and basophils INSPIRING GREATNESS Anterior Pituitary (Adenohypophysis) acidophils A, basophils B, chromophobes Cp, capillaries Ca, INSPIRING GREATNESS  Posterior Pituitary (Neurohypophysis)  Consists of:  Numerous non-myelinated nerve fibres  Supporting cells (pituicytes)  Sinusoids  Produce 2 hormones:  Oxytocin  Vasopressin  Herring bodies: collection of secretory granules at the terminal portion of axonal processing, containing either oxytocin or anti-diuretic hormone (ADH). INSPIRING GREATNESS  Thyroid Gland  Thyroid gland is made of spherical structures called follicles  The central cavity of a follicle is filled with a colloid composed of thyroglobulin  The thyroid gland has two types of endocrine cells with different functions  Follicular cells are the secretory (glandular) epithelial cells surrounding a cavity filled with a pink thyroglobulin. follicles are lined by a simple cuboidal to columnar epithelium  Follicular cells produce and secrete the hormones thyroxine and triiodothyronine.  The parafollicular cells are primarily located in clusters between follicles but can also be a part of the follicular wall.  Parafollicular cells are larger, oval in shape and have lighter stained cytoplasm than follicular cells. These cells secrete calcitonin. INSPIRING GREATNESS  Parathyroid Glands  The parathyroid glands are located on the four poles of the thyroid. Parathyroid hormone (PTH) stimulates the release of calcium by bones, absorption of calcium from food and retention of calcium by the kidneys.  Capsule - enclosed by a thin layer of connective tissue  Chief Cells - the majority of cells in the parathyroid  They have clear cytoplasm and small, centrally placed, round nuclei.  Oxyphil Cells - larger cells (8 to 12 µm diameter) with dark nuclei and strongly eosinophilic cytoplasm because of numerous mitochondria. INSPIRING GREATNESS  Adrenal Gland  An adrenal gland is located on the top of each kidney  Capsule - enclosed by a thin layer of connective tissue.  Cortex (Outer layer) - cells that synthesize and secrete steroid hormones.  Consist of three layers  Medulla (Inner layer) is made of the chromaffin cells that are arranged in cords and clumps surrounded by sinusoidal capillaries and secrete catecholamines INSPIRING GREATNESS  Adrenal Gland Cortex C, medulla M, capsule Cap, vein V, zona glomerulosa G, zona fasciculata F, zona reticularis R INSPIRING GREATNESS  Zona Glomerulosa  Zona Glomerulosa - outer zone (15%) of glomerular-like clusters of cells and secrete aldosterone.  The cells have a central nucleus and lipid filled ("foamy") cytoplasm. INSPIRING GREATNESS  Zona Fasciculata  Zona Fasciculata - middle zone (80%) of two-cell wide vertical cords that secrete cortisol.  The cells have a central nucleus and lipid filed ("foamy") cytoplasm. INSPIRING GREATNESS  Zona Reticularis  Zona Reticularis - inner zone (7%) of one-cell wide anastomosing rows that secrete precursors of testosterone.  The cells have a central nucleus and eosinophilic cytoplasm often with lipofuscin pigment  Zona reticularis borders the medulla on the inside. INSPIRING GREATNESS  Pancreas  Pancreas has both exocrine and endocrine components  The endocrine component of the pancreas consists of the islets of Langerhans, the round masses of glandular epithelial cells appearing as nodules in the endocrine pancreas.  Two principal cells in the islets are the alpha cells that secrete glucagon, and the beta cells that secrete insulin  These cell types cannot be distinguished by H&E. However, they can by electron microscopy or immunohistochemical staining for the hormones. INSPIRING GREATNESS  Slides to View  Cardio Vascular System 1. Heart 2. Aorta 3. Artery, Vein and Nerve  Endocrine System 1. Adrenal gland H1426 2. Pituitary gland 3. Thyroid gland 4. Pancreas INSPIRING GREATNESS THANK YOU INSPIRING GREATNESS