Dr.shatarat. endocrine glands

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1 Dr.shatarat endocrine glands

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3 endocrine glands Secretory cells of endocrine glands release their products, signaling molecules called hormones, into the neighboring vascularized compartment for uptake by capillaries and distribution throughout the body. There is no Junqueira's secretory duct as in exocrine glands Basic Histology Text and Atlas, 2014 th Edition Distribution by the circulation allows hormones to act on target cells with receptors for those hormones at a distance from the site of their secretion. Dr.shatarat

4 endocrine cells produce hormones that act on target cells only a short distance away Through 1- local in interstitial fluid 2-short loops of blood vessels For example :gastrin made by pyloric G cells reaches target cells in the fundic glands contact-dependent signalling in which a signaling molecule remains on the secreting cell s surface or adjacent extracellular matrix and affects target cells when the cells make contact. Juxtacrine signaling is particularly important in embryonic and regenerative tissue interactions Dr.shatarat

5 Why the CNS is not enough? Why do we need Endocrine system? Dr.shatarat

6 At puberty the female begins to undergo regular monthly cycles called sexual cycles Sexual cycles are under the control of the Brain Hypothalamus The hypothalamus acts as a pulse generator which generates the pulsatile release of The follicle-stimulating hormone (FSH) Gonadotropin releasing hormone (GnRH) (GnRH) Controls the release of the Gonadotropin from the anterior part of the pituitary gland FSH and LH Control THE OVARIAN CYCLE Dr.shatarat Controls The endometrial cycle ( menstrual cycle ) luteinizing hormone (LH)

7 Histology Dr.shatarat

8 The HEMATOXYLIN stains nucleic acids (plus calcium deposits and bacteria) blue. The EOSIN stains most proteins (actually, arginine and lysine) pink. Clear areas represent water, carbohydrate lipid, gas Dr.shatarat

9 Nuclei will always stain Blue with the Hematoxylin. The cytoplasm of cells will stain according to its composition. Dr.shatarat

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11 Dr.shatarat Cells of the adenohypophysis

12 Most of the anterior lobe of the pituitary gland has the typical organization of endocrine tissue The cells are organized in clumps and cords separated by fenestrated sinusoidal capillaries of relatively large diameter Pars distalis. This specimen of the pars distalis is stained with brilliant crystal scarlet, aniline blue, and Martius yellow to distinguish the various cell types and connective tissue stroma. The cords of cells are surrounded by a delicate connective tissue stroma stained blue. The sinusoidal capillaries are seen in close association with the parenchyma and contain erythrocytes stained yellow. In the region shown here, the acidophils (Ac) are the most numerous cell type present. Their cytoplasm stains cherry red. The basophils (Bas) stain blue. The chromophobes (Ch), although few in number in this particular region, are virtually unstained. 640 Histology: A Text and Atlas: With Correlated Cell and Molecular Biology The adenohypophysis is made of epithelia cells!!!!!!!! and vascular Dr.shatarat Sinusiods supported by a mesh of connective tissue

13 How many colors can be identified in this H&E section????? Dr.shatarat

14 Adenohypophysis high power The adenohypophysis contains 3 cell types: -acidophils (stain red) -basophils (stain blue) -chromophobes (pale stain) Dr.shatarat The adenohyphysis stains red-blue on low power because of the acidophils and basophils

15 1-Chromophils Histologists identified three types of cells according to their staining reaction, namely Basophils (10%) Acidophils (40%) 2- Chromophobes (50%) chromophils (cells which take up stain) called acidophils and basophils. The anterior pituitary also contains one type of chromophobe (cells which stain only weakly) Dr.shatarat

16 Parenchymal cells of the pars distalis to be subdivided into acidophil cells (A), basophils (B), and chromophobes (C) in which the cytoplasm is poorly stained. Also shown are capillaries and sinusoids (S) Dr.shatarat stained with Gomori trichrome. (X400

17 Cells of the adenohypophysis Chromophils Chromophobes Acidophils Basophils Dr.shatarat

18 Importance of different colors? Acidophils secrete growth hormone and prolactin Basophils secrete TSH, LH, FSH and ACTH Chromophobes are undifferentiated cells Dr.shatarat

19 Cells of the Adenohypophysis 1- Chromophobes small weakly stained cells represent stem cells or (most likely) partially degranulated chromophils Dr.shatarat

20 Chromophils Subtypes of basophilic and acidophilic cells are identified by immunohistochemistry Specific cells are usually named according to their hormone s target cells Acidophils secrete either growth hormone (somatotropin) or prolactin and are called somatotrophs and lactotrophs (or somatotropic cells and lactotropic cells), respectively. The basophilic cells are the corticotrophs, gonadotrophs, and thyrotrophs The micrograph shows somatotrophs stained using an antibody Dr.shatarat against somatotropin. (X400; Hematoxylin counterstain)

21 Chromophils Acidophils Basophils Somatotops Mammotrops Gonadotrops Thyrotrops Corticotrops Dr.shatarat

22 1- Somatotrops: LM Form ~ 50% of the total number of chromophils. Occur in clumps and clusters Central nucleus EM Rod shaped mitochondria Many rer Many secretory granules (secrete GH) Moderate Golgi Action of GH: acts on growth of long bones via insulin-like growth factors synthesized in the liver. Dr.shatarat

23 2- Mammotrops Form 15-20% of chromophils Occur singly Small polygonal cells Organelles are ill-defined During lactation organelles increase in size and number Secrete prolactin Action of prolactin: promotes milk secretion. Dr.shatarat

24 3- Gonadotrophs Form ~ 10% of chromophils. Rounded cells. Prominent nucleus. Many granules with variable size. Cytoplasm contains well developed Golgi, many rer. Secrete FSH and LH. Action of FSH: promotes ovarian follicle development and estrogen secretion in women, and spermatogenesis in men. Action of LH: promotes follicular maturation and progesterone secretion in women and Leydig secretion in men. Dr.shatarat

25 4- Thyrotrops Form ~ 5% of chromophils. Located away from sinusoids. Cytoplasm contains many small organelles. Secrete TSH. Action of TSH: stimulates thyroid hormone synthesis, storage, and liberation. Dr.shatarat

26 5- Corticotrops Form 15-20% of chromophils. Round-ovoid cells scattered through pars distalis. Eccentric nucleus with few organelles. Secrete ACTH. Action of ACTH: stimulates secretion of adrenal cortex hormones and regulated lipid metabolism. Dr.shatarat

27 * Folliculostellate cells are characterized by a star like appearance with their cytoplasmic processes encircling hormone-producing cells. They have the ability to make cell clusters or small follicles they do not produce hormones. Folliculostellate cells are interconnected by gap junctions. Based on immunocytochemical and electrophysiological studies, it is hypothesized that the network of folliculo-stellate cells interconnected by gap junctions transmits signals from the pars tuberalis to pars distalis. These signals may regulate hormone release throughout the anterior lobe of the pituitary gland. Thus, the folliculo-stellate network may appear to function in addition to the hypophyseal portal vein system Dr.shatarat

28 Neurohypophysis (Posterior Pituitary) It is composed of neural tissue, containing some 100,000 unmyelinated axons of large secretory neurons with cell bodies in the supraoptic and paraventricular nuclei of the hypothalamus Also present are highly branched glial cells called pituicytes that resemble astrocytes and are the most abundant cell type in the posterior pituitary Dr.shatarat

29 Neurohypophysis high power The neurohypophysis resembles neural tissue, with glial cells, nerve fibers, nerve endings, and intra-axonal neurosecretory granules Precursors of ADH (vasopressin) and oxytocin are synthesized in the hypothalamus and transported to the pars nervosa where processing is completed Dr.shatarat

30 Does not contain secretory cells. Contains axons of secretory nerves; their mother cells are present in the paraventricular and supraoptic hypothalamic nuclei. Pituicytes are the most numerus cells. Pituicytes resemble astrocytes. Dr.shatarat

31 Neurohypophysis high power Hering bodies are large dilated axon terminal endings that are filled with accumulated neurosecretory granules Dr.shatarat

32 Secretory neurons have larger diameter but are histologically and functionally similar to other neurons. Axons of neurons transport ADH and oxytocin into the pars nervosa. Secretory products accumulate in the distal part of the axon in Hering bodies. Hering bodies appear slightly acidophilic. Secretory products are surrounded by a membrane and bound to neurophysin. Nerve impulses trigger the release release of peptides from neurosecretory bodies. Dr.shatarat

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35 Most Oxytocin is released from paraventricular nuclei. Most ADH is released from supraoptic nuclei. Dr.shatarat

36 ADH facilitates resorption of water from the distal tubules and collecting ducts of the kidney by altering the permeability of the cells to water. Dr.shatarat

37 Oxytocin promotes contraction of smooth muscles of the uterus and myoepithelial cells of the breast. Dr.shatarat

38 Tumours of the pituitary 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 Dr.shatarat

39 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. Dr.shatarat

40 Gross anatomy Dr. Shatarat & Dr. Badran

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42 Glands drain ipsillaterally by superior, middle, and inferior thyroid veins. Dr. Shatarat & Dr. Badran

43 In the fifth week, epithelium of the dorsal wing of the third pouch differentiates into INFERIOR PARATHYROID GLAND while the ventral wing forms THE THYMUS Both gland primordia lose their connection with the pharyngeal wall, and the thymus then migrates in a caudal and a medial direction, pulling the inferior parathyroid with it Dr. Shatarat & Dr. Badran

44 Epithelium of Epithelium dorsal of wing the dorsal of wing of the fourth pharyngeal pouch forms the fourth pharyngeal pouch forms THE SUPERIOR PARATHYROID GLAND When the parathyroid gland loses contact with the wall of the pharynx, it attaches itself to the dorsal surface of the caudally migrating thyroid as the superior parathyroid gland Dr. Shatarat & Dr. Badran

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46 Parathyroid Gland low power Low power of parathyroid, showing random cords of cells. The parathyroid is somewhat lobulated in appearance and considerable adipose tissue is intermingled with secretory portions. Adipose tissue Cords of cells Dr. Shatarat & Dr. Badran

47 Parathyroid Gland high power Chief cells Oxyphil cells Dr. Shatarat & Dr. Badran 2 cells types of the Parathyroid: Chief cells secrete parathormone (PTH). They have large round nuclei with a small amount of clear cytoplasm. Oxyphil cells have smaller, darker nuclei and relatively larger amount of cytoplasm. The significance of the oxyphil cells is not clear. Some oxyphil cells show low levels of PTH synthesis, suggesting that these cells are transitional derivatives of principal cells.

48 Read only Photomicrograph of human parathyroid gland. This H&E stained specimen shows the gland with part of its connective tissue capsule (Cap). The blood vessels (BV) are located in the connective tissue septum between lobes of the gland. The principal cells are arranged in two masses (top and bottom) and are separated by a large cluster of oxyphil cells (center). The oxyphil cells are the larger cell type with prominent eosinophilic cytoplasm. They may occur in small groups or in larger masses, as seen here. The principal cells are more numerous. They are smaller, having less cytoplasm, and consequently exhibit closer proximity of their nuclei. Adipose cells (AC) are present in variable, although limited, numbers Dr. Shatarat & Dr. Badran

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50 PINEAL GLAND Also called pineal body, epiphysis cerebri is an endocrine or neuroendocrine gland that regulates daily body rhythm. It develops from neuroectoderm of the posterior portion of the roof of the diencephalon and remains attached to the brain by a short stalk. In humans, it is located at the posterior wall of the third ventricle near the center of the brain. The pineal gland is a flattened, pine cone shaped structure It measures 5 to 8 mm high and 3 to5 mm in diameter and weighs between 100 and 200 mg. Dr. Shatarat & Dr. Badran

51 The pineal gland contains two types of parenchymal cells: Pinealocytes Interstitial (glial) cells. Dr. Shatarat & Dr. Badran

52 The interstitial (glial) cells constitute about 5% of the cells in the gland. In addition to the two cell types, the human pineal gland is characterized by the presence of calcified concretions called brain sand It appears to be derived from precipitation of calcium phosphates and carbonates on carrier proteins that are released into the cytoplasm when the pineal secretions are exocytosed Dr. Shatarat & Dr. Badran

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54 Melatonin is released in the dark and regulates reproductive function in mammals by inhibiting the steroidogenic activity of the gonads Production of gonadal steroids is decreased by the inhibitory action of melatonin on neurosecretory neurons located in the hypothalamus (arcuate nucleus) that produce GnRH. Inhibition of GnRH causes a decrease in the release of FSH and LH from the anterior lobe of the pituitary gland. In addition to melatonin, extracts of pineal glands from many animals contain numerous neurotransmitters, such as serotonin, norepinephrine, dopamine, and histamine, and hypothalamic-regulating hormones, such as somatostatin and TRH. Clinically, tumors that destroy the pineal gland are associated with precocious (earlyonset) puberty. Animal studies demonstrate that information relating to the length of daylight reaches the pineal gland from photoreceptors in the retina. The pineal gland thus influences seasonal sexual activity. Recent studies in humans suggest that the pineal gland has a role in adjusting to sudden changes in day length, such as those experienced by travelers who suffer from jet lag. In addition, the pineal gland may play a role in altering emotional responses to the reduced length of day during winter in temperate and subarctic zones known as seasonal affective disorder (SAD) Dr. Shatarat & Dr. Badran

55 Endocrine Pancreas (Islets of Langerhans) Dr. Shatarat & Dr. Badran

56 Endocrine Pancreas Islets of Langerhans Low power High power Dr. Shatarat & Dr. Badran

57 Endocrine Pancreas Cells in the islets of Langerhans Alpha secrete glucagon Beta secrete insulin Delta secrete somatostatin and gastrin PP secrete pancreatic polypeptide Dr. Shatarat & Dr. Badran

58 First described by Langerhans in 1869 (as an observation on the urine of pancreactictomized dogs). In 1893 Gustave-Edouard Laguesse ( ) attached the name Langerhans to the structures. Langerhans did not suggest any function for them. The book has been reprinted with an English translation by H. Morrison. Dr. Shatarat & Dr. Badran

59 Spherical-oval cellular masses between the acini of the pancreas. Variable in size and number of cells in them. They form ~ 1 million secretroy units. Not homogeneously distributed and increase in number towards the tail. Surrounded by a very thin capsule. They have the same embryological origin as the rest of the pancreas (endoderm). Dr. Shatarat & Dr. Badran

60 Section of an adult human pancreas stained for glucagon (green) and insulin (red) Dr. Shatarat & Dr. Badran

61 In H & E cells show variation in staining reaction between acidophilia and basophilia. E.M. shows typical poly peptide secreting cells with variable amount of granules. Immunohistochemistry is the only accurate method to differentiate between cells. Dr. Shatarat & Dr. Badran

62 Major pancreatic cells cell Cell Location % Secretion Function α Peripheral ~ 20 Glucagon Blood glucose level; glycogenolysis and lipolysis β Central ~ 70 Insulin Blood glucose level δ Scattered 5-10 Somatostatin Inhibits release of other cells F (PP) Scattered <1 Pancreatic polypeptide activity of chief cells, bile secretion. pancreatic enzyme and HCO3 secretion. intestinal motility Dr. Shatarat & Dr. Badran

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68 Suprarenal (adrenal) Glands Dr. Shatarat & Dr. Badran

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71 Adrenal Histology Dr. Shatarat & Dr. Badran

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74 The gland is divided into an outer cortex and an inner medulla. The adrenal cortex is composed of three zones histologically: Outer zona glomerulosa, site for aldosterone synthesis. Central zona fasciculata produce cortisol, and Inner zona reticularis produce androgens. Dr. Shatarat & Dr. Badran

75 Zona glomerulosa Is the exclusive site of production of aldosterone. Consists ~ 15% of the cortex. Cells are arranged in closely packed clusters continuous with the next layer. Cells are small pyramidal-columnar with spherical nuclei. Clusters of cells are surrounded by fenestrated sinusoidal capillaries. Cells have abundant ser, large mitochondria with shelf-like cristae, Golgi complex, few rer, and few lipid droplets. Dr. Shatarat & Dr. Badran

76 Zona glomerulosa secretes mineralocorticoids, that function in the regulation of sodium and potassium homeostasis and water balance. The main mineralocorticoid is aldosterone. Aldosterone stimulates resorption of sodium from: Distal renal tubules. Gastric mucosa. Salivary glands. Sweat glands. The zona glomerulosa is under the feed back control of the reninangiotensin-aldosterone system. Dr. Shatarat & Dr. Badran

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78 Zona Glomerulosa Dr. Shatarat & Dr. Badran

79 Zona Fasciculata The thickest middle zone that form ~80% of the cortex. Cells are large polyhedral, arranged in long straight cords 1-2 cells thick. Cords are separated by sinusoidal capillaries. Cells are lightly stained, commonly binucleated. Cells are typical steroid synthesizing cells. Cytoplasm contains lipid droplets. Cells secrete glucocorticoids, mainly cortisol. Dr. Shatarat & Dr. Badran

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81 Glucocorticoids may have different, even opposite effects in different tissues: In the liver: conversion of aminoacids to glucose. polymerization of glucose to glycogen. uptake of aminoacids and fatty acids. In adipose tissue: breakdown of lipids to glycerol and free fatty acids. In other tissues: rate of glucose use and oxidation of fatty acids. In cells: protein synthesis and protein catabolism. Dr. Shatarat & Dr. Badran

82 Zona reticularis The inner zone, forms 5-7% of the cortex. Contains light and dark cells. Cells are smaller than the reticularis, their nuclei are more deeply stained. Cells are arranged in anastomosing cords separated by fenestrated capillaries. Cells have few lipid droplets. Cells are typical steroid-secreting cells. Their principal secretion is weak androgen (minimal glucocorticoids). Dr. Shatarat & Dr. Badran

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84 Adrenal medulla Composed of large, pale staining epithelioid cells; chromaffin cells, connective tissue, sinusoidal capillaries and nerves. The chromaffin cells are modified neurons. Myelinated, presynaptic nerves pass directly to chromaffin cells. Dr. Shatarat & Dr. Badran

85 Chromaffin cells E.M shows that there are two types of chromaffin cells: Cells containing large dense core vesicles secrete norepinephrine. Cells containing small homogeneous less dense vesicles secrete epinephrine. Dr. Shatarat & Dr. Badran

86 Glucocorticoids secreted in the cortex induce the conversion of norepinephrine to epinephrine in chromaffin cells. Most of chromaffin cells at the corticomedullary junction secrete epinephrine. Norepinephrine-secreting cells are also found in paraganglia (collections of catecholamine-secreting cells adjacent to the autonomic ganglia) and in various viscera. The conversion of norepinephrine to epinephrine (adrenalin) occurs only in chromaffin cells of the adrenal medulla About 80% of the catecholamine secreted from the adrenal is epinephrine Dr. Shatarat & Dr. Badran

87 The catecholamines, in concert with the glucocorticoids, prepare the body for the fight-or-flight response. Sudden release of catecholamines establishes conditions for maximum use of energy. Dr. Shatarat & Dr. Badran

88 Medullary chromaffin cells are innervated by preganglionic sympathetic neurons, They trigger epinephrine and norepinephrine release during stress and intense emotional reactions. Epinephrine increases: heart rate dilates bronchioles, dilates arteries of cardiac and skeletal muscle. Norepinephrine constricts: vessels of the digestive system and skin, increasing blood flow to the heart, muscles, and brain. Both hormones stimulate glycogen breakdown, elevating blood glucose levels. Together these effects augment the capability for defensive reactions or escape of stressors, the fight-or-flight response. During normal activity the adrenal medulla continuously secretes small quantities of these hormones. Dr. Shatarat & Dr. Badran

89 Thyroid gland Dr. Shatarat & Dr. Badran

90 Thyroid follicle: The structural and functional unit of the thyroid gland. Consists of a group of cells resting on the same basal lamina surrounding a lumen filled with colloid. The follicles are variable in size. Hormones are stored in the follicles. Each follicle is surrounded by variable amount of connective tissue. Dr. Shatarat & Dr. Badran

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93 Follicular cells (principal cells): Squamous-columnar cells according to activity. Basophilic cytoplasm. Nucleus: round-ovoid with 2 nucleoli. Many rer. Numerous apical lysosomes and mitochondria. Supranuclear Golgi complex. Apical microvilli. Numerous vesicles in the cytoplasm. Dr. Shatarat & Dr. Badran

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95 Parafollicular cells (Clear cells, C cells): Pale staining, larger than follicular cells. Occur singly or in clusters among follicular cells. Overlapped by follicular cells. E.M: Moderate rer. Well-developed Golgi. small, dense, basal secretory granules. Secrete calcitonin: Inhibits bone resorption by osteoclasts. Stimulated when Ca 2 is high. Dr. Shatarat & Dr. Badran

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98 Thyroid gland 1. Recognize and understand the coverings of the thyroid gland and their clinical importance. 2. Recognize and understand the main parts of the thyroid gland and their locations, relations and connections. 3. Comprehend the blood supply of the thyroid gland, their relations with recurrent and external laryngeal nerves. 4. Understand the embryological origins of the pituitary gland and its associated malformations. 5. Grasp the clinical correlations of the midline structures of neck related to the thyroid gland and differentiate between them and the those on the lateral side of the neck. 6. Recognize and understand imaging of the thyroid gland. 7. Grasp the histological structure of the thyroid gland and its cells under light. 7/14/2018 Dr.Shatarat

99 Gross anatomy 7/14/2018 Dr.Shatarat

100 It is placed anteriorly in the lower neck at the level with the 5 th cervical to the 1 st thoracic vertebrae 7/14/2018 Dr.Shatarat Transverse sections through the neck at the level of the second sixth cervical vertebrae

101 It consists of Right and left lobes connected by 7/14/2018 Dr.Shatarat a narrow isthmus

102 3- Lobs Each lobe is pear shaped Apex base its apex being directed upward as far as the oblique line on the lamina of the thyroid cartilage its base lies below at the level of the fourth or 5 th tracheal ring. It should be noted that the normal thyroid gland is nearly always asymmetric. The right lobe may be even twice as large as the left lobe. The right upper pole extends higher up in the neck, and the lower pole extends lower. Note The posteromedial aspects of the lobes are attached to the side of the cricoid cartilage by a lateral thyroid ligament 7/14/2018 Dr.Shatarat

103 4- THE ISTHMUS The isthmus extends across the midline in front of the 2 ed, 3 ed, and 4 th tracheal rings 5- Pyramidal lobe persists in at least 15% of the population is often present, and it projects upward from the isthmus Note A fibrous or fibromuscular band, the levator of the thyroid gland, musculus levator glandulae 7/14/2018 Dr.Shatarat thyroideae, sometimes descends from the body of the hyoid to the isthmus or pyramidal lobe

104 6- Coverings and fascia of the thyroid gland False capsule The thyroid gland is surrounded by True capsule 7/14/2018 Dr.Shatarat

105 A-True capsule, a thin fibrous capsule, which is formed by condensation of the stroma of the gland. It is attached by means of dense connective tissue to the cricoid cartilage (part of the larynx) and superior tracheal rings (part of the trachea). Clinical note The True capsule of thyroid capsule is much denser in front than behind and the enlarging gland therefore tends to push backwards, burying itself round the sides and even the back of the trachea and oesophagus. 7/14/2018 Dr.Shatarat cause dangerous Dyspnea Dysphagia

106 B- False capsule it is a loose sheath formed by the visceral portion of the pretracheal layer of deep cervical fascia external to the true capsule The false capsule thickens between the cricoid cartilage and thyroid gland to form the ligament of Berry (The suspensory ligament of the thyroid) gland (attaches the thyroid gland to trachea) 7/14/2018 Dr.Shatarat

107 The false capsule of the thyroid gland also attaches the gland to the larynx and even to the hyoid bone It is clear that the false capsule is attached to Both the larynx and trachea This explains why the thyroid gland follows the movements of the larynx in swallowing. Clinical note This information is important because any pathologic neck swelling that is part of the thyroid gland will move upward when the patient is asked 7/14/2018 to swallow Dr.Shatarat

108 The pretracheal layer of deep cervical fascia is attached to hyoid bone And The attachment of the sternothyroid muscles to the thyroid cartilage effectively binds down the thyroid gland to the larynx This limits upward expansion of the gland However, downward expansion has no limitation a large goitre will extend downwards into the superior mediastinum ( Plunging Goitre ) Or Retrosternal Goiter 7/14/2018 Dr.Shatarat

109 7- Relations of the Lobes A-The superior belly of the omohyoid C-The sternothyroi d B-The sternohyoid D-The anterior border of the sternocleidomastoid 7/14/2018 Dr.Shatarat

110 The anastomosis between the superior and inferior thyroid arteries. Posterior view 7/14/2018 Dr.Shatarat

111 Posterolaterally: The carotid sheath with the common carotid artery, the internal jugular vein, and the vagus nerve Medially: The larynx, the trachea, the pharynx, and the esophagus. Associated with these structures are the cricothyroid muscle and its nerve supply, the external laryngeal nerve. In the groove between the esophagus and the trachea is the recurrent laryngeal nerve 7/14/2018 Dr.Shatarat

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113 A-The superior thyroid artery B-The inferior thyroid artery C- Sometimes the thyroidea ima. A-The superior thyroid artery, a branch of the external carotid artery, descends to the upper pole of each lobe, accompanied by The External Laryngeal Nerve 7/14/2018 Dr.Shatarat

114 The superior thyroid artery on each side is related to the external laryngeal nerve, which supplies the cricothyroid muscle. Damage to the external laryngeal nerve results in an inability to tense the vocal folds and in hoarseness Thus, The Superior Thyroid Artery during surgery on the thyroid, is ligated near the gland to avoid injury to 7/14/2018 Dr.Shatarat the external laryngeal nerve

115 B-The inferior thyroid artery a branch of the thyrocervical trunk, ascends behind the gland to the level of the cricoid cartilage. It then turns medially and downward to reach the posterior border of the gland. The recurrent laryngeal nerve crosses either in front of or behind the artery, or it may pass between its branches. 7/14/2018 Dr.Shatarat

116 The terminal branches of the inferior thyroid artery on each side are related to the RECURRENT LARYNGEAL NERVE. 7/14/2018 Dr.Shatarat

117 Thus, THE INFERIOR THYROID ARTERY during surgery on the thyroid, is ligated away from the gland to avoid injury to the recurrent laryngeal nerve 7/14/2018 Dr.Shatarat

118 Variable C-The thyroidea ima, In approximately 10% of people, a thyroid ima artery arises from the brachiocephalic trunk, or the arch of the aorta, from the right common carotid subclavian, or internal thoracic arteries ascends on the anterior surface of the trachea, which it supplies, and continues to the isthmus of the thyroid gland. Clinical note The possible presence of this artery must be considered when performing procedures in the midline of the neck inferior to the isthmus because it is a potential source of bleeding 7/14/2018 Dr.Shatarat

119 Lesions of the Laryngeal Nerves The muscles of the larynx are innervated by the recurrent laryngeal nerves, with the exception of the cricothyroid muscle, which is supplied by the external laryngeal nerve. Both these nerves are vulnerable during operations on the thyroid gland because of the close relationship between them and the arteries of the gland. To be discussed next year 7/14/2018 Dr.Shatarat

120 9-The veins from the thyroid gland A-Superior thyroid vein which drains into the internal jugular vein; B-The middle thyroid vein which drains into the internal jugular vein; C-The inferior thyroid vein The inferior thyroid veins of the two sides anastomose with one another as they descend in front of the trachea. They drain into the left brachiocephalic vein in the thorax 7/14/2018 Dr.Shatarat

121 10-The lymphatic vessels of the thyroid gland communicate with a capsular network of lymphatic vessels From this network, the vessels pass initially to prelaryngeal, pretracheal, and paratracheal lymph nodes, which drain in turn to the superior and inferior deep cervical nodes Inferior to the thyroid gland, the lymphatic vessels pass directly to the inferior deep cervical lymph nodes 7/14/2018 Dr.Shatarat

122 The uppermost, just above the thyroid isthmus, in front of the cricoid cartilage, and medial to a pyramidal lobe, if present, is a constant node group of one to five nodes, which has been termed The Delphian node enlargement of which is indicative of metastasis from thyroid or laryngeal carcinoma. 7/14/2018 Dr.Shatarat

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124 In a cross section of the embryo in the area of the head and neck The following can be noticed THE PHARYNGEAL ARCHES THE PHARYNGEAL ARCHES are separated by deep clefts known as PHARYNGEAL CLEFTS with development of the arches and clefts, a number of outpocketings, The pharyngeal pouches appear 7/14/2018 Dr.Shatarat

125 Thyroid Gland 1-begins to develop during the third week as an endodermal thickening in the floor of the pharynx between the tuberculum impar and the copula at a point later indicated by the foramen cecum 7/14/2018 Dr.Shatarat Pharynx (ventral view) 4th week

126 2- It descends in front of the pharyngeal gut as a bilobed diverticulum 3- During this migration, the thyroid remains connected to the tongue by a narrow canal, the thyroglossal duct. 7/14/2018 Dr.Shatarat

127 4-As development continues, the duct elongates, and its distal end becomes bilobed. Soon, the duct becomes a solid cord of cells, and as a result of epithelial proliferation, the bilobed terminal swellings expand to form the thyroid gland 5-The thyroid gland now migrates inferiorly in the neck and passes either anterior to, posterior to, or through the developing body of the hyoid bone. 6-By the seventh week, it reaches its final position in relation to the larynx and trachea. Meanwhile, the solid cord connecting the thyroid gland to the tongue fragments and disappears. 7/14/2018 Dr.Shatarat

128 7-The site of origin of the thyroglossal duct on the tongue remains as a pit called the foramen cecum. 8-The thyroid gland may now be divided into a small median isthmus and two large lateral lobes 7/14/2018 Dr.Shatarat Pharynx and derivatives (between 6th and 7th weeks)

129 as we mentioned before, most glands have two different origins Second origin of the thyroid gland 9-The ultimobranchial bodies (from the fifth pharyngeal pouch) and neural crest cells are believed to be incorporated into the thyroid gland, where they form the parafollicular cells, which produce calcitonin. 7/14/2018 Dr.Shatarat

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131 Congenital Anomalies of the Thyroid Gland 1-Agenesis of the Thyroid Failure of development of the thyroid gland may occur and is the commonest cause of cretinism 2-Incomplete Descent of the Thyroid The descent of the thyroid may be arrested at any point between the base of the tongue and the trachea Lingual thyroid is the most common form of incomplete descent The mass of tissue 7/14/2018 Dr.Shatarat

132 Aberrant thyroid tissue may be found anywhere along the path of descent of the thyroid gland. It is commonly found in the base of the tongue, just behind the foramen cecum, and is subject to the same diseases as the thyroid gland itself. caution!!! A mass in the posterior midline might be the only thyroid in the patient s body 7/14/2018 Dr.Shatarat

133 7/14/2018 Dr.Shatarat yroglossal Duct and Thyroid Abnormalities

134 3-Persistent Thyroglossal Duct Conditions related to a persistence of the thyroglossal duct usually appear in childhood, in adolescence, or in young adulthood 7/14/2018 Dr.Shatarat

135 Thyroglossal Duct and Thyroid Abnormalities A thyroglossal cyst may lie at any point along the migratory pathway of the thyroid gland but is always near or in the midline of the neck by its name, it is a cystic remnant of the thyroglossal duct, Although approximately 50% of these cysts are close to or just inferior to the body of the hyoid bone they may also be found at the base of the tongue or close to the thyroid cartilage. Sometimes a thyroglossal cyst is connected to the outside by a fistulous canal, a thyroglossal fistula. Such a fistula usually arises secondarily after rupture of a cyst but may be present at birth. 7/14/2018 Dr.Shatarat

136 Thyroglossal cyst. These cysts, which are remnants of the thyroglossal duct, may be anywhere along the migration pathway of the thyroid gland. They are commonly found behind the arch of the hyoid bone. An important diagnostic characteristic is their midline 7/14/2018 Dr.Shatarat

137 Branchial Fistulas Branchial fistulas occur when the second pharyngeal arch fails to grow caudally over the third and fourth arches, leaving remnants of the second, third, and fourth clefts in contact with the surface by a narrow canal. Such a fistula, found on the lateral aspect of the neck directly anterior to the sternocleidomastoid muscle, usually provides drainage for a lateral cervical cyst These cysts, remnants of the cervical sinus, are most often just below the angle of the jaw Frequently a lateral cervical cyst is not visible at birth but becomes evident as it enlarges during childhood. Patient with a lateral cervical cyst. These cysts are always on the lateral side 7/14/2018 of the neck in front of the sternocleidomastoid muscle. They Dr.Shatarat commonly lie under the angle of the mandible and do not enlarge until later in life.

138 4-Thyroglossal Sinus (Fistula) Occasionally, a thyroglossal cyst ruptures spontaneously, producing a sinus). Usually, this is a result of an infection of a cyst. All remnants of the thyroglossal duct should be removed surgically 7/14/2018 Dr.Shatarat

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140 1-As the lateral lingual swellings increase in size, they overgrow the tuberculum impar and merge, forming the anterior two-thirds, or body, of the tongue Since the mucosa covering the body of the tongue originates from the first pharyngeal arch, sensory innervation to this area is by the mandibular branch of the trigeminal nerve. The body of the tongue is separated from the posterior third by a V-shaped groove, the terminal sulcus 2-The posterior part, or root, of the tongue originates from the second, third, and part of the fourth pharyngeal arch The fact that sensory innervation to this part of the tongue is supplied by the glossopharyngeal nerve indicates that tissue of the third arch overgrows that of the second. Some of the tongue muscles probably differentiate in situ, but most are derived from myoblasts originating in occipital somites. Thus, tongue musculature is innervated by the hypoglossal nerve. 7/14/2018 Dr.Shatarat

141 in the floor of the pharynx Tuberculum impar Copula (hypobranchial eminence Epiglottal swelling Foramen cecum Palatine tonsil Root of tongue 7/14/2018 Dr.Shatarat

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146 Metastatic disease to the thyroid is common; it likely relates to its rich blood supply of approximately 560 ml/100 g tissue/min (a flow rate per gram of tissue that is second only to the adrenal glands) 7/14/2018 Dr.Shatarat

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