SISTEM ENDOKRIN

RINThe hypophysis
=pituitary body

•       Hipofisis (Yunani hypo, dibawah, + physis, pertumbuhan),

•       = master of glands

•       beratnya sekitar 0.5 gram,

•       dimensi normalnya pada manusia sekitar 10 x 13 x 6 mm.

Letak : Kelenjar ini berada di rongga tulang sphenoid/sella turcica

STRUKTUR

•       Lobus : Anterior et Posterior

•       Lobus Anterior : lebih besar, mirip ren. Terdiri dari pars anterior dan   pars intermedia, keduanya dipisahkana oleh celah sempit

•       Banyak vaskularisasi dan terdiri dari sel epitel  yang ukurannya bervariasi  menyusun jaringan tracecular seperti alveoli dan dipisahkan oleh pembuluh darah yang lebar dan tipis.

•       The pars intermedia merupakan lembaran tipis terdiri dari pembuluh darah dan jaringan sel granuler diantara matriks koloid

•       pars intermedia  à sekresi substrat yang mengakibatkan konstriksi pembuluh darah à meningkatkan tekanan darah  karena adanya stimulasi pada otot polos ; juga meningkatkan sekresi urin, gland. Mammae, dan cairan cerebrovascular . Juga mempengaruhu metabolisme umum karbohidrat dengan meningkatkan proses glycogenolysis pada liver

•         The pars anterior à efek stimulasi pertumbuhan tulang skeleton dan mungkin  connective tissues secara keseluruhan          4

•       Pembesaran hypophysis à  acromegalyà  gradual enlargement of the face, hands, and feet, with headache and often a peculiar type of blindness. This blindness is due to the pressure of the enlarging hypophysis on the optic chiasma

Glandula Thyreiodea

•       The Thyroid Gland = Thyroid Body

•       Kelenjar tiroid adalah salah satu dari kelenjar endokrin terbesar pada tubuh manusia. Kelenjar ini dapat ditemui di bagian depan leher, sedikit di bawah laring.

•       Bentuk seperti Kupu2 à Terdiri dari 2 lobus : Lobus dextra et sinistra yang dihubungkan oleh  isthmus pada bagian tengahnya.

•       Berat berkisar 30 gram.

•       Sedikit berat pada perempuan terutama saat menstruasi dan hamil

Lokasi Anatomi-batas2

•       Bagian lateral/permukaan superficial convex, tertutup fascia pretracheal & m. Sternocleidomastoideus, Omohyoideus, the Sternohyoideus and Sternothyreoideus

•       Medialnya adalah cart. thyroid and cricoid , trachea, m. Constrictor pharyngis inferior dan  bagian  posterior Cricothyreoideus, esophagus ,a. Thyroidea superior and inferior thyroid nerbus  recurrent.

•       Bagian anteriornya tipis   pada posteriornya menutupi a. Carotis communis dan glandula parathyroid.

FUNGSI

1. mengatur kecepatan tubuh membakar energi
2. membuat protein
3. mengatur sensitivitas tubuh terhadap hormon lainnya.

Regulasi metabolisme dan keseimbangan kalsium à T4 and T3 hormones stimulate every tissue in the body to produce proteins and increase the amount of oxygen used by cells. The harder the cells work, the harder the organs work. The calcitonin hormone works together with the parathyroid hormone to regulate calcium levels in the body.

Levels of hormones secreted by the thyroid are controlled by the pituitary gland's thyroid-stimulating hormone, which in turn is controlled by the hypothalamus.

3 HORMON PENTING

yaitu:

1. Triodotironin
2. Tiroksin
3. Kalsitonin

Triodotironin dan Tiroksin mengatur laju metabolisme dengan cara mengalir bersama darah dan memicu sel untuk mengubah lebih banyak glukosa.

Jika Tiroid mengeluarkan terlalu sedikit Triodotironin dan Tiroksin, maka tubuh akan merasa kedinginan, letih, kulit mengering dan berat badan bertambah. Sebaliknya jika terlalu banyak, tubuh akan berkeringat, merasa gelisah, tidak bisa diam dan berat badan akan berkurang.

STRUKTUR CAPSULA

•       Kelenjar tiroid ditutupi oleh selubung fibrosa tipis,= capsula glandulae thyroidea, terdiri dari lapisan internal dan eksternal.

•       Lapisan eksternal anterior bersambung dg fascia cervicalis lamina pretrachealis , posteriorolateral bersambung  dengan selubung karotis

STRUKTUR LOBUS

•       Lobus – lobusnya berbentuk konus

•       Tiap lobus panjang sekitar 5 cm. long; lebarnya sekitar 3 cm dengan ketebalan ± 2 cm

•        isthmus gld. Thyreoidea menyatukan lobus dex et sin pada bagian paling bawah dengan panjang dan kedalaman  ± 1.25 cm dan biasanya tertutup oleh cincin tracche ke 2 dan 3 à anatomi bervariasi

•       Variasi : Adanya Lobus ketiga = pyramidal lobus à bentuk konus

    seringkali berkembang dari isthmus , sering   

     berada di kiri , kadang terbagi menjadi 2 bagian.

•       Kadang terlihat jaringan seperti sabuk fibrous pada bagian tulang hyoid bone, dibawah isthmus /pyramidal lobe=Levator glandulæ thyreoideæ.        

•         Tambak glandula kecil pada  jaringan  thyroid pada lateral / diatas isthmus =glandulæ thyreoideæ accessoriæ

HISTOLOGI

Kapsul tipis dari jaringan ikat  yang berbentuk irreguler

Jika dipotong berwarna  merah kecoklatan dan terdiri dari vesikel2 yang berisi cairan kuning dan terpisah satu dengan yang lain oleh jaringan ikat.

Vessels and Nerves

•       A. thyroidea ima à from the innominate artery or the arch of the aorta, which ascends upon the front of the trachea. The arteries are remarkable for their large size and frequent anastomoses.

•       The veins form a plexus on the surface of the gland and on the front of the trachea; from this plexus the superior, middle, and inferior thyroid veins arise; the superior and middle end in the internal jugular, the inferior in the innominate vein.

•        The capillary bloodvessels form a dense plexus in the connective tissue around the vesicles, between the epithelium of the vesicles and the endothelium of the lymphatics, which surround a greater or smaller part of the circumference of the vesicle.

•       The lymphatic vessels run in the interlobular connective tissue, not uncommonly surrounding the arteries which they accompany, and communicate with a net-work in the capsule of the gland; they may contain colloid material. They end in the thoracic and right lymphatic trunks. The nerves are derived from the middle and inferior cervical ganglia of the sympathetic.

•       Synthesis of the thyroid hormones, as seen on an individual thyroid follicular cell:[12]

•       - Thyroglobulin is synthesized in the rough endoplasmic reticulum and follows the secretory pathway to enter the colloid in the lumen of the thyroid follicle by exocytosis.

•       - Meanwhile, a sodium-iodide (Na/I) symporter pumps iodide (I-) actively into the cell, which previously has crossed the endothelium by largely unknown mechanisms.

•       - This iodide enters the follicular lumen from the cytoplasm by the transporter pendrin, in a purportedly passive manner.[13]

•       - In the colloid, iodide (I-) is oxidized to iodine (I0) by an enzyme called thyroid peroxidase.

•       - Iodine (I0) is very reactive and iodinates the thyroglobulin at tyrosyl residues in its protein chain (in total containing approximately 120 tyrosyl residues).

•       - In conjugation, adjacent tyrosyl residues are paired together.

•       - The entire complex re-enters the follicular cell by endocytosis.

•       - Proteolysis by various proteases liberates thyroxine and triiodothyronine molecules, which enters the blood by largely unknown mechanisms.

Thymus

•       Bahasa Yunani kuno =  θυμός (thumos) = marah = hati, jiwa, hasrat, hidup

•       Mungkin karena lokasinya di dada dekat emosi atau = daun thyme (also in Greek θύμος or θυμάρι) = "warty excrescence", karena bentuknya seperti daun thyme

•       = organ of the immune system. The thymus “memacu" T-lymphocytes (T cells)= sel kekebalan tubuh.

•       Terdiri dari 2 lobus

•       Lokasi : anterior superior mediastinum,  depan jantung di bawah sternum

•       Secara histologi  : medulla (tengah) dan cortex (tepi) yang dibungkus kapsul.

•       Membesar dan aktif  dan periode remaja kemudian atropi dan stromanya digantikan oleh jarngan adiposa .Namun  residual T lymphopoiesis berlanjut saat dewasa

•       pinkish-gray color, soft, permukaan berlobus2

•       Saat lahir 5 cm x, 4 cm x 6

•       Membesar saat usia anak2 dan atropi saat pubertas (20 to 37 grams), usia of 75 years, the thymus weighs only 6 grams. In children the thymus is grayish-pink in colour and in adults it is yellow.

•       The thymus will, if examined when its growth is most active, be found to consist of two lateral lobes placed in close contact along the middle line, situated partly in the thorax, partly in the neck, and extending from the fourth costal cartilage upward, as high as the lower border of the thyroid gland. It is covered by the sternum, and by the origins of the sternohyoidei and sternothyreoidei. Below, it rests upon the pericardium, being separated from the aortic arch and great vessels by a layer of fascia. In the neck, it lies on the front and sides of the trachea, behind the sternohyoidei and sternothyreoidei. The two lobes differ slightly in size and may be united or separated.

STRUCTURE

•       Each lateral lobe is composed of numerous lobules held together by delicate areolar tissue; the entire organ being enclosed in an investing capsule of a similar but denser structure. The primary lobules vary in size from that of a pin's head to that of a small pea, and are made up of a number of smallnodules or follicles.

•       The follicles are irregular in shape and are more or less fused together, especially toward the interior of the organ. Each follicle is from 1 to 2 mm in diameter and consists of a medullary and a cortical portion,^[13] and these differ in many essential particulars from each other.

•       Cortex

•       The cortical portion is mainly composed of lymphoid cells, supported by a network of finely-branched epithelial reticular cells, which is continuous with a similar network in the medullary portion. This network forms an adventitia to the blood vessels.

•       The cortex is the location of the earliest events in thymocyte development, where T cell receptor gene rearrangement and positive selection takes place.

•       Medulla

•       In the medullary portion, the reticulum is coarser than in the cortex, the lymphoid cells are relatively fewer in number, and there are found peculiar nest-like bodies, the concentric corpuscles of Hassall. These concentric corpuscles are composed of a central mass, consisting of one or more granular cells, and of a capsule formed of epithelioid cells. They are the remains of the epithelial tubes, which grow out from the third branchial pouches of the embryo to form the thymus. Each follicle is surrounded by a vascular plexus, from which vessels pass into the interior, and radiate from the periphery toward the center, forming a second zone just within the margin of the medullary portion. In the center of the medullary portion there are very few vessels, and they are of minute size.

•       The medulla is the location of the latter events in thymocyte development. Thymocytes that reach the medulla have already successfully undergone T cell receptor gene rearrangement and positive selection, and have been exposed to a limited degree of negative selection. The medulla is specialised to allow thymocytes to undergo additional rounds of negative selection to remove auto-reactive T-cells from the mature repertoire. The gene AIRE is expressed by the thymic medullary epithelium, and drives the transcription of organ-specific genes such as insulin to allow maturing thymocytes to be exposed to a more complex set of self-antigens than is present in the cortex.

VASCULARISASI

•       The arteries supplying the thymus are derived from the internal thoracic artery, and from the superior thyroid artery and inferior thyroids.

•       The veins end in the left brachiocephalic vein (innominate vein), and in the thyroid veins[disambiguation needed].

•       The nerves are exceedingly minute; they are derived from the vagi and sympathetic nervous system. Branches from the descendens hypoglossi and phrenic reach the investing capsule, but do not penetrate into the substance of the organ.

•       In the two thymic lobes, hematopoietic precursors from the bone-marrow, referred to as thymocytes, mature into T-cells. Once mature, T-cells emigrate from the thymus and constitute the peripheral T-cell repertoire responsible for directing many facets of the adaptive immune system. Loss of the thymus at an early age through genetic mutation (as in DiGeorge Syndrome[14]) results in severe immunodeficiency and a high susceptibility to infection.[15]

•       The stock of T-lymphocytes is built up in early life, so the function of the thymus is diminished in adults. It is largely degenerated in elderly adults and is barely identifiable, consisting mostly of fatty tissue, but it continues its endocrine function.[16] Involution of the thymus has been linked to loss of immune function in the elderly, susceptibility to infection and to cancer.

•       The stock of T-lymphocytes is built up in early life, so the function of the thymus is diminished in adults. It is largely degenerated in elderly adults and is barely identifiable, consisting mostly of fatty tissue, but it continues its endocrine function.[16] Involution of the thymus has been linked to loss of immune function in the elderly, susceptibility to infection and to cancer.

•       The ability of T-cells to recognize foreign antigens is mediated by the T cell receptor. The T cell receptor undergoes genetic rearrangement during thymocyte maturation, resulting in each T-cell bearing a unique T-cell receptor, specific to a limited set of peptide:MHC combinations. The random nature of the genetic rearrangement results in a requirement of central tolerance mechanisms to remove or inactivate those T cells which bear a T cell receptor with the ability to recognise self-peptides.

•       Micrograph showing a thymic corpuscle (Hassall corpuscle), a characteristic histologic feature of the human thymus. H&E stain.

•       The cortex and medulla play different roles in the development of T-cells. Cells in the thymus can be divided into thymic stromal cells and cells of hematopoietic origin (derived from bone marrow resident hematopoietic stem cells). Developing T-cells are referred to as thymocytes and are of hematopoietic origin. Stromal cells include thymic cortical epithelial cells, thymic medullary epithelial cells, and dendritic cells.

•       A rare population of hematopoietic progenitor cells enter the thymus from the blood, and expands by cell division to generate a large population of immature thymocytes.[17]

•       Immature thymocytes each make distinct T-cell receptors by a process of gene rearrangement. This process is error-prone, and some thymocytes fail to make functional T-cell receptors, whereas other thymocytes make T-cell receptors that are autoreactive.[18]

•       Immature thymocytes undergo a process of selection, based on the specificity of their T-cell receptors. This involves selection of T-cells that are functional (positive selection), and elimination of T-cells that are autoreactive (negative selection). The medulla of the thymus is the site of T Cell maturation.

GASTER

•       The gastric mucosa is the mucous membrane layer of the stomach which contains the glands and the gastric pits.

•       about 1 mm thick and its surface is smooth, soft, and velvety. It consists of epithelium, lamina propria, and the muscularis mucosae.

•       When examined with a lens, the inner surface of the mucous membrane presents a peculiar honeycomb appearance from being covered with funnel-like depressions or foveolae of a polygonal or hexagonal form, which vary from 0.12 to 0.25 mm. in diameter. These are the ducts of the gastric glands, and at the bottom of each may be seen one or more minute orifices, the openings of the gland tubes.

•       Gastric glands are simple or branched tubular glands that emerge on the deeper part of the gastric foveola, inside the gastric areas and outlined by the folds of the mucosa.

•       There are three types of glands: cardiac glands (in the proximal part of the stomach), oxyntic glands (the dominating type of gland), and pyloric glands. The cardiac glands mainly contain mucus producing cells. The bottom part of the oxyntic glands is dominated by zymogen (chief) cells that produce pepsinogen (an inactive precursor of the pepsin enzyme). Parietal cells, which secrete hydrochloric acid are scattered in the glands, with most of them in the middle part.

•       The upper part of the glands consist of mucous neck cells; in this part the dividing cells are seen. The pyloric glands contain mucus-secreting cells. Several types of endocrine cells are found in all regions of the gastric mucosa. The pyloric glands contain gastrin producing cells (G cells); this hormone stimulates acid production from the parietal cells. ECL (enterochromaffine-like) cells, found in the oxyntic glands release histamine, which also is a powerful stimulant of the acid secretion. The A cells produce glucagon, which mobilizes the hepatic glycogen, and the enterochromaffin cells produce serotonin, which stimulates the contraction of the smooth muscles.

•       The surface of the mucous membrane is covered by a single layer of columnar epithelium . This epithelium commences very abruptly at the cardiac orifice, where there is a sudden transition from the stratified epithelium of the esophagus. The epithelial lining of the gland ducts is of the same character and is continuous with the general epithelial lining of the stomach. An important iodine-concentration by sodium-iodide symporter (NIS) is present in mucinous cells of surface epithelium and gastric pits of the fundus and pyloric part of the stomach.

PANCREAS

•       Herophilus (335–280 BC), a Greek anatomist and surgeon. Only a few hundred years later, Rufus of Ephesus, another Greek anatomist, gave the pancreas its name. The term "pancreas" is derived from the Greek πᾶν ("all", "whole"), and κρέας ("flesh")[8] – it is presumed because of its fleshy consistency.

•       producing several important hormones, including insulin, glucagon, somatostatin, and pancreatic polypeptide, and a digestive organ, secreting pancreatic juice containing digestive enzymes that assist the absorption of nutrients and the digestion in the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids in the chyme.

•       Under a microscope, stained sections of the pancreas reveal two different types of parenchymal tissue. Lightly staining clusters of cells are called islets of Langerhans, which produce hormones that underlie the endocrine functions of the pancreas. Darker-staining cells form acini connected to ducts. Acinar cells belong to the exocrine pancreas and secrete digestive enzymes into the gut via a system of ducts.

•       The pancreas is a dual-function gland, having features of both endocrine and exocrine glands.

•       The part of the pancreas with endocrine function is made up of approximately a million cell clusters called islets of Langerhans. Four main cell types exist in the islets. They are relatively difficult to distinguish using standard staining techniques, but they can be classified by their secretion: α cells secrete glucagon (increase glucose in blood), β cells secrete insulin (decrease glucose in blood), delta cells secrete somatostatin (regulates/stops α and β cells), and PP cells or gamma cells, secrete pancreatic polypeptide.

•       The islets are a compact collection of endocrine cells arranged in clusters and cords and are crisscrossed by a dense network of capillaries. The capillaries of the islets are lined by layers of endocrine cells in direct contact with vessels, and most endocrine cells are in direct contact with blood vessels, either by cytoplasmic processes or by direct apposition. According to the volume The Body, by Alan E. Nourse,the islets are "busily manufacturing their hormone and generally disregarding the pancreatic cells all around them, as though they were located in some completely different part of the body." The islet of Langerhans plays an imperative role in glucose metabolism and regulation of blood glucose concentration.

•       The pancreas as an exocrine gland helps out the digestive system. It secretes pancreatic fluid that contains digestive enzymes that pass to the small intestine. These enzymes help to further break down the carbohydrates, proteins, and lipids (fats) in the chyme.

•       In humans, the secretory activity of the pancreas is regulated directly via the effect of hormones in the blood on the islets of Langerhans and indirectly through the effect of the autonomic nervous system on the blood flow.

•       Sympathetic (adrenergic)

•       α2: decreases secretion from beta cells, increases secretion from alpha cells, β2: increases secretion from beta cells

•       Parasympathetic (muscarinic)

•       M3: increases stimulation of alpha cells and beta cells[7]

•       The pancreas lies in the epigastrium and left hypochondrium areas of the abdomen

•       It is composed of the following parts:

•       The head lies within the concavity of the duodenum.

•       The uncinate process emerges from the lower part of head, and lies deep to superior mesenteric vessels.

•       The neck is the constricted part between the head and the body.

•       The body lies behind the stomach.

•       The tail is the left end of the pancreas. It lies in contact with the spleen and runs in the lienorenal ligament.

•       The superior pancreaticoduodenal artery from gastroduodenal artery and the inferior pancreaticoduodenal artery from superior mesenteric artery run in the groove between the pancreas and the duodenum and supply the head of pancreas. The pancreatic branches of splenic artery also supply the neck, body and tail of the pancreas. The largest of those branches is called the arteria pancreatica magna; its occlusion, although rare, is fatal.

•       The body and neck of the pancreas drain into splenic vein; the head drains into the superior mesenteric and portal veins.

•       Lymph is drained via the splenic, celiac and superior mesenteric lymph nodes.

GLANDULAE SUPRARENALIS

•       = Adrenal Capsule

•       two small flattened bodies of a yellowish color

•       situated at the back part of the abdomen,  behind the peritoneum, and immediately above and in front of the upper end of each kidney; hence their name.

•       The right one is somewhat triangular in shape, bearing a resemblance to a cocked hat; the left is more semilunar, usually larger, and placed at a higher level than the right. They vary in size in different individuals, being sometimes so small as to be scarcely detected

•       usual size is from 3 to 5 cm. in length, rather less in width, and from 4 to 6 mm. in thickness. Their average weight is from 1.5 to 2.5 gm. each.

•       The right suprarenal is situated behind the inferior vena cava and right lobe of the liver, and in front of the diaphragm and upper end of the right kidney.

•       It is roughly triangular in shape; its base, directed downward, is in contact with the medial and anterior aspects of the upper end of the right kidney. It presents two surfaces for examination, an anterior and a posterior.

•       The anterior surface looks forward and lateralward, and has two areas: a medial, narrow, and non-peritoneal, which lies behind the inferior vena cava; and a lateral, somewhat triangular, in contact with the liver.

•       The upper part of the latter surface is devoid of peritoneum, and is in relation with the bare area of the liver near its lower and medial angle, while its inferior portion is covered by peritoneum, reflected onto it from the inferior layer of the coronary ligament; occasionally the duodenum overlaps the inferior portion.

•       A little below the apex, and near the anterior border of the gland, is a short furrow termed the hilum, from which the suprarenal vein emerges to join the inferior vena cava.

•       The posterior surface is divided into upper and lower parts by a curved ridge: the upper, slightly convex, rests upon the diaphragm; the lower, concave, is in contact with the upper end and the adjacent part of the anterior surface of the kidney.

•       The left suprarenal, slightly larger than the right, is crescentic in shape, its concavity being adapted to the medial border of the upper part of the left kidney. It presents a medial border, which is convex, and a lateral, which is concave; its upper end is narrow, and its lower rounded. Its anterior surface has two areas: an upper one, covered by the peritoneum of the omental bursa, which separates it from the cardiac end of the stomach, and sometimes from the superior extremity of the spleen; and a lower one, which is in contact with the pancreas and lienal artery, and is therefore not covered by the peritoneum. On the anterior surface, near its lower end, is a furrow or hilum, directed downward and forward, from which the suprarenal vein emerges. Its posterior surface presents a vertical ridge, which divides it into two areas; the lateral area rests on the kidney, the medial and smaller on the left crus of the diaphragm.

•       The surface of the suprarenal gland is surrounded by areolar tissue containing much fat, and closely invested by a thin fibrous capsule, which is difficult to remove on account of the numerous fibrous processes and vessels entering the organ through the furrows on its anterior surface and base.               

•         Small accessory suprarenals (glandulæ suprarenales accessoriæ) are often to be found in the connective tissue around the suprarenals. The smaller of these, on section, show a uniform surface, but in some of the larger a distinct medulla can be made out.

•       On section, the suprarenal gland is seen to consist of two portions :

•       1. external or cortical

•       2. internal or medullary. The former constitutes the chief part of the organ, and is of a deep yellow color; the medullary substance is soft, pulpy, and of a dark red or brown color.

SUBSTANTIA CORTICALIS

•       consists of a fine connective-tissue net-work, in which is imbedded the glandular epithelium.

•       The epithelial cells are polyhedral in shape and possess rounded nuclei; many of the cells contain coarse granules, others lipoid globules. Owing to differences in the arrangement of the cells, three distinct zones can be made out:

•        (1) the zona glomerulosa, situated beneath the capsule, consists of cells arranged in rounded groups, with here and there indications of an alveolar structure; the cells of this zone are very granular, and stain deeply.

•       (2) The zona fasciculata, continuous with the zona glomerulosa, is composed of columns of cells arranged in a radial manner; these cells contain finer granules and in many instances globules of lipoid material. (3) The zona reticularis, in contact with the medulla, consists of cylindrical masses of cells irregularly arranged; these cells often contain pigment granules which give this zone a darker appearance than the rest of the cortex.

SUBSTANTIA MEDULLARIS

•       extremely vascular, and consists of large chromaphil cells arranged in a network.

•       The irregular polyhedral cells have a finely granular cystoplasm that are probably concerned with the secretion of adrenalin. In the meshes of the cellular network are large anastomosing venous sinuses (sinusoids) which are in close relationship with the chromaphil or medullary cells. In many places the endothelial lining of the blood sinuses is in direct contact with the medullary cells. Some authors consider the endothelium absent in places and here the medullary cells are directly bathed by the blood.

•       This intimate relationship between the chromaphil cells and the blood stream undoubtedly facilitates the discharge of the internal secretion into the blood. There is a loose meshwork of supporting connective tissue containing non-striped muscle fibers. This portion of the gland is richly supplied with non-medullated nerve fibers, and here and there sympathetic ganglia are found.

Vessels and Nerves

The arteries supplying the suprarenal glands are numerous and of comparatively large size; they are derived from the aorta, the inferior phrenic, and the renal. They subdivide into minute branches previous to entering the cortical part of the gland, where they break up into capillaries which end in the venous plexus of the medullary portion.       

 

The suprarenal vein returns the blood from the medullary venous plexus and receives several branches from the cortical substance; it emerges from the hilum of the gland and on the right side opens into the inferior vena cava, on the left into the renal vein.     

•       The lymphatics end in the lumbar glands.               

•         The nerves are exceedingly numerous, and are derived from the celiac and renal plexuses, and, according to Bergmann, from the phrenic and vagus nerves. They enter the lower and medial part of the capsule, traverse the cortex, and end around the cells of the medulla. They have numerous small ganglia developed upon them in the medullary portion of the gland.  

•         In connection with the development of the medulla from the sympathochromaffin tissue, it is to be noted that this portion of the gland secretes a substance, adrenalin, which has a powerful influence on those muscular tissues which are supplied by sympathetic fibers.