Endocrine anatomy29042010 pdf


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Endocrine anatomy29042010 pdf

  3. 3. proencephalon = telencephalon (cerebral hemispheres) + diencephalon midbrain = mesencephalon = tectum + cerebral peduncles • brain stem = the brain minus the cerebrum and cerebellum. • BRAIN STEM = the stalk of the brain connecting the cerebral hemispheres with the spinal cord and compromising the midbrain (mesencephalon), pons and medulla ablongata. • ????//// DIENCEPHALON IS CONSIDERED PART OF BRAIN STEM BY SOME.
  4. 4. Endocrine Glands 1) Hypothalamus 2) Pineal body. 3) Pituitary gland. 4) Thyroid gland. 5) Parathyroid glands. 6) Pancreas (pancreatic islets of Langerhans). 7) Adrenal glands. 8) Gonads (ovary/ testis).
  5. 5. The hypothalamus • The hypothalamus forms the floor of the 3rd ventricle. • It includes, from before backwards, • the optic chiasma, the tuber cinereum, the infundibular stalk (leading down to the posterior lobe of the pituitary), the mamillary bodies and the posterior perforated substance. • In each of these there is a number of cell masses or nuclei and a fibre pathway—the medial forebrain bundle—which runs throughout the length of the hypothalamus and serves to link it with the midbrain posteriorly and the basal forebrain areas anteriorly. • Sherrington described the hypothalamus as the head ganglion of the autonomic system. • It is largely concerned with autonomic activity and can be divided into a posteromedial sympathetic area and an anterolateral area concerned with parasympathetic activity
  6. 6. The hypothalamus (continue) • The hypothalamus plays an important part in endocrine control by the formation of releasing factors or release-inhibiting factors. • These substances, following their secretion into the hypophyseal portal vessels, influence the production by the cells of the anterior pituitary of adrenocorticotrophin (ACTH), follicle-stimulating hormone, luteinizing hormone, prolactin, somatotrophin, thyrotrophin and melanocyte- stimulating hormone. • The hormones oxytocin and vasopressin (anti-diuretic hormone, ADH) are produced by neurones in the hypothalamus and released at their axon terminals in the posterior pituitary
  7. 7. Clinical features (skip) 1) Lesions of the hypothalamus may result in a variety of autonomic disturbances, e.g. somnolence (somnolentia), disturbances of temperature regulation and obesity, as well as a variety of endocrine abnormalities, e.g. hypogonadism and hypothyroidism. 2) Damage to the supraoptic nuclei or the infundibular stalk leads to diabetes insipidus.
  8. 8. The thalamus and 3rd ventricle in coronal section.
  9. 9. The pineal gland • The pineal gland rests between the two superior colliculi (corpora quadrigemina) and is attached by a stalk to the posterior dorsal thalamus. • It secretes melatonin and has an important role in setting the circadian rhythm. • (When calcified, the pineal gland is easily identified on skull radiographs. It may then give the important radiological sign of lateral displacement by a space-occupying lesion of the cerebral hemisphere). The latter is a radiological finding you can skip it.
  10. 10. Skip????// • The small, red, pinecone–shaped pineal gland, or epiphysis cerebri, is part of the epithalamus. The pineal gland contains neurons, glial cells, and special secretory cells called pinealocytes . • Pinealocytes synthesize the hormone melatonin which is derived from molecules of the neurotransmitter serotonin. • Melatonin slows the maturation of sperm, oocytes, and reproductive organs by inhibiting the production of a hypothalamic releasing factor that stimulates FSH and LH secretion. • Collaterals from the visual pathways enter the pineal gland and affect the rate of melatonin production. • Melatonin production rises at night and declines during the day. This cycle is apparently important in regulating circadian rhythms, our natural awake-asleep cycles. • This hormone is also a powerful antioxidant that may help protect CNS tissues from toxins generated by active neurons and glial cells.
  11. 11. The Pituitary Gland
  12. 12. The sphenoid Bone / Sella Tursica • The general shape of the sphenoid has been compared to a giant bat with its wings extended. The wings can be seen most clearly on the superior surface . • A prominent central depression between the wings cradles the pituitary gland below the brain. This recess is called the hypophysial fossa, and the bony enclosure is called the sella turcica . • The anterior clinoid processes are posterior projections of the lesser wings of the sphenoid. The tuberculum sellae forms the anterior border of the sella turcica; the dorsum sellae forms the posterior border. • A posterior clinoid process extends laterally on either side of the dorsum sellae. • The lesser wings are triangular in shape, with the superior surfaces supporting the frontal lobe of the brain. • The inferior surfaces form part of the orbit and the superior part of the superior orbital fissure, which serves as a passageway for blood vessels and cranial nerves of the eye.
  13. 13. The pituitary gland (hypophysis cerebri) • This is an example of a ‘two in one’ organ of which nature is so keen; compare the two glandular components of the suprarenal cortex and medulla, and the exocrine and endocrine parts of the pancreas, testis and ovary. • The pituitary comprises a larger anterior and smaller posterior lobe, the latter connected by the hollow infundibulum (pituitary stalk) to the tuber cinereum in the floor of the 3rd ventricle.  The two lobes are connected by a narrow zone termed the pars intermedia.  The pituitary lies in the cavity of the pituitary fossa covered over by the diaphragma sellae, which is a fold of dura mater. This fold has a central aperture through which passes the infundibulum. Below is the body of the sphenoid, laterally lies the cavernous sinus and its contents separated by dura mater, with intercavernous sinuses communicating in front, behind and below. The optic chiasma lies above, immediately in front of the infundibulum.
  14. 14. Hypophyseal Portal Vessels
  15. 15. Structure • The anterior lobe is extremely cellular and consists of chromophobe, eosinophilic and basophilic cells. • The pars intermedia contains large colloid vesicles reminiscent of the thyroid. • The posterior lobe is made up of nerve fibers whose cell stations lie in the hypothalamus.
  16. 16. Development • The posterior lobe is a cerebral diverticulum. • The anterior lobe and the pars intermedia develop from Rathke’s pouch in the roof of the primitive buccal cavity. • Occasionally a tumour grows from remnants of the epithelium of this pouch (craniopharyngioma). • These tumours are often cystic and calcified.
  17. 17. Clinical features (skip) • Tumours of the pituitary, as well as forming intracranial space- occupying lesions, may have two special features; their endocrine disturbances and their relationship to the optic chiasma. • Chromophobe adenoma is the commonest pituitary tumour. As it enlarges it expands the pituitary fossa (sella turcica) and this may be demonstrated radiologically. • Compression of the optic chiasma produces the very rapid typical bitemporal hemianopia. • The tumour itself is non-secretory and gradually destroys the normally functioning gland. • The patient develops hypopituitarism with loss of sex characteristics, hypothyroidism and hypoadrenalism. • In childhood there is an arrest of growth. • As the tumour extends there may be involvement of the hypothalamus with diabetes insipidus and obesity
  18. 18. Clinical features (skip) • The eosinophil adenoma secretes the pituitary growth hormones. If it occurs before puberty, which is unusual, it produces gigantism; after puberty it results in acromegaly. • The basophil adenoma is small, produces no pressure effects and may be associated with Cushing’s syndrome, although this more often results from hyperplasia or tumour of the suprarenal cortex. • Pituitary tumours may be approached through a frontal bone flap or, using the fibre- optic endoscope, through the nasal cavity and sphenoid sinus. • The close relationship of the pituitary to the sphenoid sinus makes it possible to insert fibre-optic instruments into the pituitary gland by a transnasal, transsphenoidal approach. This is now the preferred approach to surgery of pituitary tumours.
  19. 19. The descent of the thyroid, showing possible sites of ectopic thyroid tissue or thyroglossal cysts,and also the course of a thyroglossal fistula. (The arrow shows the further descent of the thyroid which may take place retrosternally into the superior mediastinum.)
  20. 20. The Thyroid Gland • The thyroid is made up of : 1. The isthmus—overlying the 2nd and 3rd rings of the trachea; 2. The lateral lobes— each extending from the side of the thyroid cartilage downwards to the 6th tracheal ring; 3. An inconstant pyramidal lobe projecting upwards from the isthmus, usually on the left side, which represents a remnant of the embryological descent of the thyroid. Relations: • The gland is enclosed in the pretracheal fascia, • covered by the strap muscles • overlapped by the sternocleidomastoids. • The anterior jugular veins course over the isthmus. When the thyroid enlarges, the strap muscles stretch and adhere to the gland. so that, at operation, they often appear to be thin layers of fascia.
  21. 21. The Thyroid Gland (continue) • On the deep aspect of the thyroid lie the larynx and trachea, with the pharynx and oesophagus behind and the carotid sheath on either side. • Two nerves lie in close relationship to the gland; in the groove between the trachea and oesophagus lies the recurrent laryngeal nerve and deep to the upper pole lies the external branch of the superior laryngeal nerve passing to the cricothyroid muscle.
  22. 22. Blood supply  Three arteries supply and three veins drain the thyroid gland: • the superior thyroid artery arises from the external carotid and passes to the upper pole; • the inferior thyroid artery arises from the thyrocervical trunk of the 1st part of the subclavian artery and passes behind the carotid sheath to the back of the gland; • the thyroidea ima artery is inconstant; when present, it arises from the aortic arch or the brachiocephalic artery; • the superior thyroid vein drains the upper pole to the internal jugular vein; • the middle thyroid vein drains from the lateral side of the gland to the internal jugular; • the inferior thyroid veins (often several) drain the lower pole to the brachiocephalic veins. • As well as these named branches, numerous small vessels pass to the thyroid from the pharynx and trachea.
  23. 23. Development of Thyroid Gland • Thyroid gland develops mainly from the thyroglossal duct. • Parafollicular cells are derived from the caudal pharyngeal complex (from 4th and 5th pharyngeal pouch). • After formation of the pharyngeal arches, the medial ends of the two mandibular arches are separated by • Tuberculum impar = A midline structure in the floor of the pharynx. • Immediately the tuberculum impar the epithelium of the floor of the pharynx shows a thickening. • This thickening is soon depressed to form a diverticulum called the thyroglossal duct.
  24. 24. Development of Thyroid Gland (continue) • The site of the diverticulum is now seen as a depression called the foramen caecum. • The diverticulum grows down in the midline into the neck. • Its tip bifurcates. • Proliferation of the cells of this bifid end gives rise to the • Two lobes of the thyroid gland. • The developing thyroid gland comes into intimate contact with The caudal pharyngeal complex and fuses with it. • Cells arising from this complex are believed to give origin to the parafollicular cells of the thyroid.
  25. 25. The Parathyroid Glands The normal sites of the parathyroid glands (posterior aspect).
  26. 26. The relationship of the recurrent laryngeal nerve to the thyroid gland and the inferior thyroid artery. (a) The nerve is usually deep to the artery but (b) may be superficial to it or (c) pass through its branches.
  27. 27. Normal and abnormal sites of the parathyroid glands (lateral view).
  28. 28. The Parathyroid Glands • These are usually four in number, a superior and inferior on either side; • however, the numbers vary from two to six. • 90% are in close relationship to the thyroid, • 10% are aberrant, the latter invariably being the inferior glands. • Each gland is about the size of a split pea and is of a yellowish-brown colour.
  29. 29. The Parathyroid Glands (continue) • The superior parathyroid is more constant in position than the inferior gland. • It usually lies at the middle of the posterior border of the lobe of the thyroid above the level at which the inferior thyroid artery crosses the recurrent laryngeal nerve. • The inferior parathyroid is most usually situated below the inferior artery near the lower pole of the thyroid gland. • The next commonest site is within 1cm of the lower pole of the thyroid gland. • Aberrant inferior parathyroids may descend along the inferior thyroid veins in front of the trachea and may even track into the superior mediastinum in company with thymic tissues. • Less commonly, the inferior gland may lie behind and outside the fascial sheath of the thyroid and be found behind the oesophagus or even in the posterior mediastinum. • Only on extremely rare occasions are the glands actually completely buried within thyroid tissue.
  30. 30. Development • The superior parathyroids differentiate from the 4th branchial pouch. • The inferior gland develops from the 3rd pouch in company with the thymus, • As the thymus descends, the inferior parathyroid is dragged down with it. • It is thus easily understood that the inferior parathyroid may be dragged beyond the thyroid into the mediastinum.
  31. 31. The derivatives of the branchial pouches. The inferior parathyroid migrates downwards from the 3rd pouch whereas the superior parathyroid (4th pouch) remains stationary.
  32. 32. Clinical Features (skip) 1. These possible aberrant sites are, of course, of great importance in searching for a parathyroid adenoma in hyperparathyroidism. 2. The parathyroids are usually safe in subtotal thyroidectomy because the posterior rim of the thyroid is preserved. However, they may be inadvertently removed or damaged, with resultant tetany due to the lowered serum calcium.
  34. 34. The Suprarenal Glands • The suprarenal glands are retroperitoneal, cap the upper poles of the kidneys and lie against the crura of the diaphragm. • The left is related anteriorly to the stomach across the lesser sac, • the right lies behind the right lobe of the liver and tucks medially behind the inferior vena cava. • Each gland, weighing only 3 to 4 g, • Each gland has three arteries supplying it: • direct branch from the aorta; branch from the phrenic artery; branch from the renal artery. • The single main vein drains from the hilum of the gland into the nearest available vessel—the inferior vena cava on the right, the renal vein on the left.
  35. 35. The Suprarenal Glands • The suprarenal gland comprises a cortex and medulla, which represent two developmentally and functionally independent endocrine glands within the same anatomical structure. • The medulla is derived from the neural crest (neuroectoderm) whose cells also give rise to the sympathetic ganglia. • The cortex, on the other hand, is derived from the mesoderm. • The suprarenal medulla receives preganglionic sympathetic fibres from the greater splanchnic nerve and secretes adrenaline and noradrenaline. • The cortex secretes the adrenocortical hormones.
  36. 36. PANCREAS
  37. 37. The pancreas • The pancreas lies retroperitoneally in roughly the transpyloric plane. • For descriptive purposes it is divided into head, neck, body and tail. • Relations • The head lies in the C-curve of the duodenum and sends out the uncinate process which hooks posteriorly to the superior mesenteric vessels as these travel from behind the pancreas into the root of the mesentery. • Posteriorly lie the inferior vena cava, the commencement of the portal vein, aorta, superior mesenteric vessels, the crura of diaphragm, • coeliac plexus, the left kidney and suprarenal gland. • The tortuous splenic artery runs along the upper border of the pancreas. • The splenic vein runs behind the gland, receives the inferior mesenteric vein and joins the superior mesenteric to form the portal vein behind the pancreatic neck.
  38. 38. The pancreas • To complete this list of important posterior relationships, the common bile duct lies either in a groove in the right extremity of the gland or embedded in its substance, as it passes to open into the second part of the duodenum. • Anteriorly lies the stomach separated by the lesser sac. • To the left, the pancreatic tail lies against the hilum of the spleen.
  39. 39. The pancreas • The blood supply • Blood is supplied from the splenic and the pancreaticoduodenal arteries; • the corresponding veins drain into the portal system. • The lymphatics • The lymphatics drain into nodes which lie along its upper border, in the groove between its head and the duodenum, and along the root of the superior mesenteric vessel.
  40. 40. Cell of the Pancreas • Pancreatic islets, accounts for only 1% of the pancreatic cell population. • There are two million islets in the normal pancreas. 1. Alpha cells ------- Glucagon. 2. Beta cells --------- Insulin. 3. Delta cells -------- somatostain.(GHIH) 4. F cells ------------ PP (pancreatic polypeptide)
  41. 41. Development • The pancreas develops from a larger dorsal diverticulum from the duodenum and a smaller ventral out pouching from the side of the common bile duct. • The ventral pouch swings round posteriorly to fuse with the lower aspect of the dorsal diverticulum, trapping the superior mesenteric vessels between the two parts. • The ducts of the two formative segments of the pancreas then communicate; • that of the smaller takes over the main pancreatic flow to form the main duct, • leaving the original duct of the larger portion of the gland as the accessory duct.
  42. 42. Testis and epididymis
  43. 43. Transverse section of the testis
  44. 44. Testis and Epididymis • The left testis lies at a lower level than the right within the scrotum; • rarely, this arrangement is reversed. • Each testis is contained by a white fibrous capsule, the tunica albuginea, and each is invaginated anteriorly into a double serous covering, • the tunica vaginalis, just as the intestine is invaginated anteriorly into the peritoneum. • Along the posterior border of the testis, rather to its lateral side, lies the epididymis, which is divided into an expanded head, a body and a pointed tail inferiorly. • Medially, there is a distinct groove, the sinus epididymis, between it and the testis. The epididymis is covered by the tunica vaginalis except at its posterior margin which is free or, so to say, ‘extraperitoneal’. • The testis and epididymis each bear at their upper extremities a small stalked body, termed respectively the appendix testis and appendix epididymis (hydatid of Morgagni). • The appendix testis is a remnant of the upper end of the paramesonephric (Müllerian) duct; the appendix epididymis is a remnant of the mesonephros. • These structures, being stalked, are liable to undergo torsion.
  45. 45. Blood Supply • The testicular artery arises from the aorta at the level of the renal vessels. • It anastomoses with the artery to the vas, supplying the vas deferens and epididymis, which arises from the inferior vesical branch of the internal iliac artery. • This cross-connection means that ligation of the testicular artery is not necessarily followed by testicular atrophy. • The pampiniform plexus of veins becomes a single vessel, the testicular vein, in the region of the internal ring. • On the right this drains into the inferior vena cava, • on the left into the renal vein.
  46. 46. Lymph Drainage + Nerve Supply • The lymphatic drainage of the testis obeys the usual rule; it accompanies the venous drainage and thus passes to the para- aortic lymph nodes at the level of the renal vessels. • Free communication occurs between the lymphatics on either side; • there is also a plentiful anastomosis with the paraaortic intrathoracic nodes and, in turn, with the cervical nodes, • so that spread of malignant disease from the testis to the nodes at the root of the neck is not rare. • Nerve supply • T10 sympathetic fibres via the renal and aortic plexus. • These convey afferent (pain) fibres—hence referred pain from the testis to the loin.
  47. 47. Structure of the Testis • The testis is divided into 200–300 lobules each containing one to three seminiferous tubules. • Each tubule is some 2 feet (62 cm) in length when teased out, and is thus obviously coiled and convoluted to pack away within the testis. • The tubules anastomose posteriorly into a plexus termed the rete testis from which about a dozen fine efferent ducts arise, pierce the tunica albuginea at the upper part of the testis and pass into the head of the epididymis,which is actually formed by these efferent ducts coiled within it. • The efferent ducts fuse to form a considerably convoluted single tube which constitutes the body and tail of the epididymis;
  48. 48. Development and Descent of the Testis • This is important and is the key to several features which are of clinical interest. • The testis arises from a germinal ridge of mesoderm in the posterior wall of the abdomen just medial to the mesonephros • and links up with the epididymis and vas, which differentiate from the mesonephric duct. • As the testis enlarges, it also undergoes a caudal migration according to the following timetable: • 3rd month (of fetal life) reaches the iliac fossa; • 7th month traverses the inguinal canal; • 8th month reaches the external ring; • 9th month descends into the scrotum.
  49. 49. Development and Descent of the Testis • Amesenchymal strand, the gubernaculum testis, extends from the caudal end of the developing testis along the course of its descent to blend into the scrotal fascia. • The exact role of this structure in the descent of the testis is not known; theories are that it acts as a guide (gubernaculum = rudder) or that its swelling dilates the inguinal canal and scrotum. I • n the third fetal month, a prolongation of the peritoneal cavity invades the gubernacular mesenchyme and projects into the scrotum as the processus vaginalis. • The testis slides into the scrotum posterior to this, projects into it and is therefore clothed front and sides with peritoneum. About the time of birth this processus obliterates, leaving the testis covered by the tunica vaginalis. • Very rarely, fragments of adjacent developing organs —spleen or suprarenal — are caught up and carried into the scrotum along with the testis.
  50. 50. Clinical Features(skip) The testis arises at the level of the mesonephros at the level of L2/3 When searching for secondary lymphatic spread from a neoplasm of the testis, Rarely, a rapidly developing varicocele (dilatation of the pampiniform plexus of veins) The testis may fail to descend and may rest anywhere along its course— intra- abdominally, within the inguinal canal, at the external ring or high in the scrotum. Abnormalities of the obliteration of the processus vaginalis lead to a number of extremely common surgical conditions of which the indirect inguinal hernia is the most important.
  51. 51. Types of hydrocele. (a) Vaginal hydrocele, (b) congenital hydrocele, (c) infantile hydrocele, (d) hydrocele of the cord. (The tube at the upper end of each diagram represents the internal inguinal ring. Yellow = hydrocele, Brown = vas and epididymis)
  52. 52. The Ovary ◊The Fallopian tube, ovary and broad ligament
  53. 53. The Ovary • The ovary is an almond-shaped organ, 1.5 in (4 cm) long, attached to the back of the broad ligament by the mesovarium. • The ovary has two other attachments, the infundibulopelvic ligament, (sometimes called the suspensory ligament of the ovary), along which pass the ovarian vessels and lymphatics from the side wall of the pelvis, • and the ovarian ligament, which passes to the cornu of the uterus. • Relations • The ovary is usually described as lying on the side wall of the pelvis opposite the ovarian fossa, • which is a depression bounded by the external iliac vessels in front and the ureter and internal iliac vessels behind and which contains the obturator nerve. • However, the ovary is extremely variable in its position and is frequently found prolapsed into the pouch of Douglas in perfectly normal women. • The ovary, like the testis, develops from the genital ridge and then descends into the pelvis. In the same way as the testis, it therefore drags its blood supply and lymphatic drainage downwards with it from the posterior abdominal wall.
  54. 54. Blood supply, lymph drainage and nerve supply • Blood supply • is from the ovarian artery which arises from the aorta at the level of the renal arteries. • The ovarian vein drains, on the right side, to the inferior vena cava, on the left, to the left renal vein, exactly comparable to the venous drainage of the testis. • Lymphatics pass to the aortic nodes at the level of the renal vessels, following the general rule that lymphatic drainage accompanies the venous drainage of an organ. • Nerve supply is from the aortic plexus (T10). • All these structures pass to the ovary in the infundibulopelvic ligament
  55. 55. Structure • The ovary has no peritoneal covering; the serosa ends at the mesovarian attachment. • It consists of a connective tissue stroma containing Graafian follicles at various stages of development, corpora lutea and corpora albicantia (hyalinized, regressing corpora lutea, which take several months to absorb completely). • The surface of the ovary in young children is covered with a so- called ‘germinal epithelium’ of cuboidal cells. • It is now known, however, that the primordial follicles develop in the ovary in early fetal life and do not differentiate from these cells. • In adult life, in fact, the epithelial covering of the ovary disappears, leaving only a fibrous capsule termed the tunica albuginea. • After the menopause the ovary becomes small and shrivelled; in old age the follicles disappear completely. Thank You