Endocrine system Histolgy

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Endocrine system:

Endocrine system

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When functioning properly, the endocrine system, is like a fine-tuned orchestra. Because the endocrine system is comprised of several organs, many functions can go awry. The endocrine system carries out a wide variety of physiological processes through chemical messengers called "hormones"

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Synthesis and secretion of chemical messenger known as hormones. glands secrete hormones into the bloodstream. The circulating blood then delivers hormones to all the cells of body. Hormones act only on those target cells that have specific surface receptor to bind that hormone. This leads to alteration in the activities of target cells. Hormone producing elements in the body may be in the form of discrete organ, tissue or unicellular structure Dr Pankaj Maheria 3

Type of hormones:

Type of hormones Protein and glycoproteins molecules Small peptide molecules Amino acid derivatives Steroids derived from cholesterol Dr Pankaj Maheria 4

Division :

Division Major endocrine organs Endocrine components within other solid organs Diffuse endocrine system Dr Pankaj Maheria 5

Pituitary gland:

Pituitary gland Small bean shaped Weighs : 0.5 gm Measurement : 15 mm transversely 10 mm anteroposteriorly 6 mm vertically Sella turcica Master endocrine gland Dr Pankaj Maheria 6

Development :

Development Oral ectoderm and neurectoderm Posterior part or neurohypophysis : Neurectoderm Downward growth of diencephalon Anterior part or adenohypophysis Oral ectoderm Outpouching ( Rathke’s pouch) from the roof of primitive oral cavity. Dr Pankaj Maheria 7

Subdivision :

Subdivision Dr Pankaj Maheria 8 PARTS COMPONENTS LOBES Adenohypophysis Pars Distalis Anterior Lobe Pars Tuberalis Pars Intermedia Neurohypophysis Pars Nervosa Posterior Lobe Infundibular Stalk

Hormones :

Hormones Functional group Act directly on non-endocrine tissue Grwoth hormne , prolactine , antidiureticmhormone , Oxytocin and melanocyte stimulating hormones Modulate the secretory activity of other endocrine glands. Thyroid stimulating hormones, adenocorticotrophic hormone and gonadotrophic hormone ,follicle stimulating hormone, luteinising hormones Dr Pankaj Maheria 9

Blood supply:

Blood supply Dr Pankaj Maheria 10

Adenohypophysis :

Adenohypophysis Cells are arranged in irregular cords / clusters in between thin walled fenestrated sinusoids Classification of cells Chromophils Acidophils Basophilis Chromophobes Dr Pankaj Maheria 11

Chromophils: Acidophils:

Chromophils : Acidophils Stain pink (acidophilic) hence called Acidophils or Alpha cells. More abundant in peripheral part Smaller than basophil with large and more numerous granules. Includes two major cell type: Somatotropes - produce growth hormone or somatotropin . Mammotropes produce prolactin Dr Pankaj Maheria 12

Chromophils: Basophils:

Chromophils : Basophils Stain blue with hematoxylin and other basic dyes. Considered as degranulated (resting) chromophils More abundant in core of the gland. Large than acidophil. Dr Pankaj Maheria 13

Chromophils: Basophils:

Chromophils : Basophils Includes different cell type. Gonadotropes : Follicle stimulating hormones (FSH) Leutinizing hormone (LH) Corticotropes Adrenocorticotropin (ACTH) Thyrotropes Thyrotropin (thyroid stimulating hormone ) Dr Pankaj Maheria 14

Pars Intermedia:

Pars Intermedia Located between pars distalis and pars nervosa. Consists mainly of Basophils In Amphilia , cells are involved in synthesis of MSH ( Melanocyte stimulating hormone) which act on melanocytes of skin to produce melanin. However the function of these cells in human is not clearly known. Produce MSH, ACTH and lipotropic hormone (LPH) Rudimentary in human. Contains Rathke’s cysts, small irregular colloid containing cavities lined with cuboidal epithelium. Dr Pankaj Maheria 15

Pars Tuberalis:

Pars Tuberalis Funnel shaped superior extension of the pars distalis surrounds the infundibular stem. Similar to pars distalis but it contains mostly gonadotropins . Consists of cords or clusters of chromophil (mostly basophilc ) and chromophobic cells. Dr Pankaj Maheria 16

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Chromophils Acidophils Basophils Somatotrophs Lactotrophs gonadotrophs thyrotrophs Cortocotrophs Diagram Shape of cells Round or Oval Small irregular Large rounded polyhedral Polygonal Affinity for stain Oragne G Carmine & Erythrosin Aniline blue & PAS + Aniline blue & PAS + Aniline blue & PAS (Weakly) Size of secreting granules 350-400 nm 200 nm (600 nm during lactation ) 275-375 nm 120-200 nm 375-550 nm Hormone GH Prolactin (PRL) Lh and FSH TSH ACTH and MSH Site of action Skeletal tissue Mammary gland Ovary & Testis Thyroid Adrenal cortex & pigmenaation of skin Dr Pankaj Maheria 17


Neurohypophysis Consist of median eminence, infundibular stalk & pars nervosa(posterior lobe of Hypophysis ) Stains poorly Does not synthesize any hormone Contains many unmyelinated axons whose cell bodies are located mainly in the supraoptic and periventricular nucleus in the hypothalamus and Pituicytes . Dr Pankaj Maheria 18


Neurohypophysis Axons passing from these nuclei to the pars nervosa are together termed hypothalamo hypophysial tract. Axons contain neurosecretory granules and exhibit large granules filled dilatations called Herring Bodies . Two hormones - Oxytocin Vasopressin (ADH) Dr Pankaj Maheria 19

Thyroid gland :

Thyroid gland Butterfly shaped gland In front of upper part of trachea. Brownish red in colur Weighs 25 gm Two capsule Inner fibroelastic true capsule Outer false capsule derived form pretracheal fascia. Dr Pankaj Maheria 20

Structure : stroma:

Structure : stroma Connective tissue framework. Capsule Intralobular loose areolar connective tissue Dr Pankaj Maheria 21

Structure : parenchyma :

Structure : parenchyma Thyroid follicles : Structural and functional unit. Spheroidal Single layers of cuboidal epithelial cells (follicular cell) bounded by basement membrane. Homogeneous colloid material which stain pink color in stain Dr Pankaj Maheria 22

Differences between resting and active follicles. :

Differences between resting and active follicles. Resting follicles Follicles are large Lined by squamous epithelium Nucleus : drak Large amount of acidophilic colloid in the lumen Active follicle Follicles are small Lined by cuboidal to low columnar epithelium Nucleus : pale Little amount of colloid with scalloped border. Dr Pankaj Maheria 23

Parafollicular cells (C cell ):

Parafollicular cells (C cell ) Neuroendocrine cells Scattered cells in the follicular lining Identified ultrastructurally only by immunocytochemical method. Calcitonin : antagonist of parathormone . Dr Pankaj Maheria 24

Parathyroid galnd:

Parathyroid galnd Two pairs gland. Small oval structures , yellowish in colour Essential for life Dr Pankaj Maheria 25

Structures :

Structures Capsule : Thin connective tissue Septae Reticular fibres Parenchyma Secretory endocrine cells Arrange in clusters Cells : two type Chief or principal cells Oxyphil cells Dr Pankaj Maheria 26

Chief cells :

Chief cells Smaller and numerous Polygonal in shape Rounded central nucleus Pale eosinophilic or clear cytopalsm . Systhesis and secretion: parathyroid hormones or parathormone (PTH) Dr Pankaj Maheria 27

Oxyphil cells :

Oxyphil cells Larger and less numerous Polygonal in shape Dark necleus . Copius eosinophilic cytoplasm. Appear after puberty Increases with age Function : not known Dr Pankaj Maheria 28

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As age advances the gland is infiltrate by adipose tissue. Adipocytes : more than 50% Secretion of hormones controlled by blood calcium and phosphate level. Not by any other hormones Dr Pankaj Maheria 29

Adrenal gland:

Adrenal gland Small Flattened Right : triangular and left: crescentric Weighs : 5 to 8 gms Closely applied to upper pole of kidney Contain two functionally different type of endocrine tissue which have distinctly different embryological origin. Part: Yellow peripheral region : cortex Brown central region : medulla Dr Pankaj Maheria 30

Adrenal cortex:

Adrenal cortex Three histological zone Zona glomerulosa Zona fasciculata Zona reticularis Cells of cortex: Typical steroid synthesizing cells Lipid droplets Many mitochondria with long tubular cristae sER Dr Pankaj Maheria 31

Adrenal cortex:

Adrenal cortex Do not store the hormones. Relase hormones by diffusion through plamsa membrane and not by exocytosis Controlled by: ACTH for glucocorticoid Renin – angiotensin system for mineralocorticoid Dr Pankaj Maheria 32

Zona glomerulosa:

Zona glomerulosa Outermost zone beneath capsule. 15% total volume. Rounded or arched clusters of columnar or pyramidal cells. Acidophilic cytoplasm with few lipid droplets. Fenestrated capillaries. Secretion: Mineralocorticoids , primarily aldosterone . Dr Pankaj Maheria 33

Zona fasciculata:

Zona fasciculata Intermediate zone 65% of total volume Straight parallel cords of polyhedral cells Pale sating cytoplasm with many lipid droplet Spongiocytes Fenestrated capillaries Secretion: Glucocortocoids Dr Pankaj Maheria 34

Zona reticularis:

Zona reticularis Inner most zone 5- 10 % of total volume Small irregular anastomosing cord of cells . Smaller and more acidophilc than other Cytoplasm Elongated mictochondria , glycogen, lipofusion pigments and few lipid droplet Secretion: Small amount of androgen Dr Pankaj Maheria 35

Adrenal medulla:

Adrenal medulla Clumps or cords of chromaffin cells ( Phaeochromocyte ) Polyhedral in shape Fine reticular fibres Few parasympathetic ganglion cells Dr Pankaj Maheria 36

Adrenal medulla: Chromaffin cells:

Adrenal medulla: Chromaffin cells Modified sympathetic postganglionic neurons which lose their axons and dendrites to become secretory cells Neural crest Stain : Chromium salt Dr Pankaj Maheria 37

Adrenal medulla:Chromaffin cells:

Adrenal medulla:Chromaffin cells Two different type Epinephrine: small less electron dense granules Norepinephrine : large more electron dense granules Dr Pankaj Maheria 38

Pineal gland:

Pineal gland Small flattened conical gland Pia mater which forms the capsule Trabecula Blood vessels Unmylinated postganglionic sympathetic fibres dervied from superiro cervical ganglion Synthesis and secretion of hormones: melatonin Dr Pankaj Maheria 39

Structures :

Structures Two type of cells Pinealocytes astroglial cells or interstitial cells Brain sand (Corpora arenacea ) Basophilic bodies found extracellular in matrix Composition : Concentric layers of clacium and magnesium phosphate Increase with age Landmark for raiologist Dr Pankaj Maheria 40

Pinealocytes :

Pinealocytes Main cells type 95% of cell population Modified neuron Large irregular nuclei and prominent nucleoli Long tortuous cytoplasmic processes ending in relation to blood vessels as swelling Store granules containing melatonin and its precursor serotonin. Dr Pankaj Maheria 41

Astroglial cells:

Astroglial cells Neuroglial cells Dark elongated nuclei Long cytoplasmic processes that support the pinealocytes and blood vessels. Dr Pankaj Maheria 42

Function :

Function Role of pineal as endocrine gland is poorly understood. Diurnal and circadian rhythms Dr Pankaj Maheria 43

Applied :

Applied Gigantism Acromegaly Diabetes insipidus Hypothyroiddism Adult : myxoedema Child : cretinism Hyperthyroidism Hyperadrenalism Cushing’s syndrome Conn’s syndrome Hypoadrenalism Addison’s disease Dr Pankaj Maheria 44

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Dr Pankaj Maheria 45

Thank you…….:

Thank you……. Dr Pankaj Maheria 46

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Characteristic features of different types of chromophils . Differences between resting and active follicles. Function of pineal galnd Write the layer of adrenal gland and hormone secreted by them? What is function of chief cell of parathyroid gland? Dr Pankaj Maheria 47

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