Histology exam 5
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- what are the organs of the endocrine system?
- pituitary, thyroid, parathyroid, adrenal & pineal glands
- what are the clusters of cells of the endocrine system?
- pancreatic islets of Langerhans, theca interna in the ovary, interstitial cells in the testis
- what are the individual cells of the endocrine system?
- enteroendocrine cells in the digestive tract that belong to the DNES
- which organs which are not exclusively endocrine secrete hormones?
- kidney, heart, liver, thymus, and placenta
- list the three groups of hormones with examples
-
(1) Steroid and FA derivs
testosterone, cortisol
(2) AA derivs
thyroxine, epinephrine
(3) Peptides and Proteins
growth hormone, insulin - Do most organelles of the secretory cells show polarity?
- NO
- which secretory cells are the exception to the rule that organelles don't show polarity?
- follicle cells of the thyroid & individual endocrine cells which are contained in an epithelium (e.g. enteroendocrine cells in the digestive tract)
- what are two major differences between the endocrine and nervous systems?
-
(1) Time Until Effect
Nervous -- ms
Endocrine -- minutes --> hours
(2) Target Distance
Nervous -- local
Endocrine -- diffuse, distant - what are the two different glands of the pituitary gland?
- adenohypophysis & neurohypophysis
- describe the embryological development of the adenohypophysis
-
develops from a hollow evagination (Rathke's pouch), an outgrowth of stomadeal ectoderm from the roof of the mouth
Rathke's pouch loses its connection with the oral cavity and ascends toward the base of the brain where it contacts the neurohypophysis - what are the four subdivisions of the adenohypophysis?
-
(1) pars distalis
(2) pars tuberalis
(3) cystic remnants of Rathke's pouch
(4) pars intermedia - pars distalis
- largest subdivision; forms from the anterior wall of Rathke’s pouch, constituting > 95% of adenohypophysis
- pars tuberalis
- forms a collar of cells around the infundibulum of the neurohypophysis
- cycstic remnants of Rathke’s pouch
- small cysts persisting from the original cavity of Rathke’s pouch
- pars intermedia
- forms from the posterior wall of Rathke’s pouch at the interface of the adeohypophysis with the pars nervosa of the neurohypophysis; these cells also surround small cystic remnants of Rathke’s pouch; this subdivision is rudimentary in humans.
- describe the embryological development of the neurohypophysis
- develops as an outgrowth from the hypothalamus of the diencephalon of the brain, and retains its connection with the brain, abutting the posterior wall of Rathke's pouch
- what are the two subdivisions of the neurohypophysis?
- infundibulum and the pars nervosa
-
acidophils
- def
- two types -
hormone-containing granules in the cytoplasm of these cells stain with acidic dyes (e.g. eosin)
somatoitropes & mammotropes - somatotropes
- secrete somatotropin (growth hormone, GH), which promotes growth (anabolic)
- mammotropes
- secrete prolactin which stimulates milk production
-
basophils
- def
- types -
hormone-containing granules in the cytoplasm of these cells stain with basic dyes (e.g. hematoxylin)
thyrotropes, gonadotropes & adrenocorticotropes - thyrotropes
- secrete thyroid stimulating hormone (TSH) which stimulates thyroid hormone synthesis and release
- gonadotropes
- secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH); both hormones present in males, however in males LH can be referred to as interstitial cell stimulating hormone (ICSH); regulate egg and sperm maturation and sex hormone production
- adrenocorticotropes
- secrete adrenocorticotropic hormone (ACTH) which regulates glucocorticoid secretion by adrenal gland
- chromophobes
- cells with sparse granule content that do not stain with either hemotoxylin or eosin; may be degranulated cells or reserve, undifferentiated cells
-
Waddya think? -
get it? - describe the distribution of cell types in the adenohypophysis
-
pars distalis contains all five cell types
pars tuberalis contains gonadotropes only
pars intermedia contains adrenocorticotropes only - show how adenohypophseal hormone secretion is regulated by factors produced by neurons in the hypothalamus
- factors transported via axons --> terminate in capillary bed at base of hypothalamus (median eminence) --> nuerohormones released / uptake by capillaries --> hypophyseal portal vessels --> second capillary network (within adenohypophysis) --> stimulate or inhibit secretion of hormones
- infundibulum
-
extension from the hypothalamus; continuous with the pars nervosa
contains the hypothalamo-hypophyseal tract which consists of axons from neurons whose cell bodies are located in the supraoptic and paraventricular nuclei of the hypothalamus - pars nervosa
- contains axons and axon terminals of the neurons forming the hypothalamo-hypophyseal tract
- herring bodies
-
(of the pars nervosa)
expanded axon terminals which accumulate secretory granules containing oxytocin or ADH (vasopressin) - oxytocin
- causes smooth muscle and myoepithelial cell contraction
- ADH
- acts on the kidney tubules to prevent water loss
- thyroid gland consists of what two structures?
-
(1) thyroid follicles
(2) parafollicular cells - thyroid follicles basic structure
- hollow spheres composed of a single layer of follicle cells which form an epithelium (follicular epithelium)
- does the follicular epithelium demonstrate cellular polarity?
- yes, these cells have apical and basal surfaces
- what do follicle cells secrete?
- thyroglobulin
- thyroglobulin
- a glycoprotein secreted by follicle cells; stored in the center of the follicle; contains modified tyrosine AAs that constitute the thyroid hormones (thyroxine T4 and T3)
- what do thyroid hormones do?
- they regulate the basal metabolic rate
- parafollicular cells
-
(C cells, clear cells)
occur within the follicular epithelium and in small clusters b/t follicles; possess secretory granules containing the hormone calcitonin, which acts to inhibit bone resorption, lowering calcium levels; belong to the diffuse neuroendocrine system (DNES) - list the four basic steps of synthesis and release of thyroid hormones
-
(1) follicle cells synth and secrete thyroglobulin from their apical surfaces into the follicle lumen
(2) tyrosines of tyroglobulin are iodinated in the follicle lumen and are rearranged to form the thyroid hormones T3 and T4
(3) iodinated thyroglobulin resorbed by pinocytosis into follicle cells, where it is hydrolyzed, liberating T3 & T4
(4) T3 & T4 released from basolateral surfaces of the follicle cell & enter the blood stream - active follicle (thyroid)
- follicle cells are cuboidal to columnar and are involved involved with both secretion and resorption of thyroglobulin
- inactive follicle (thyroid)
- follicle cells are squamous, reflecting the paucity of secretory organelles and the lack of synthetic and uptake activity
-
parathyroid glands
- def
- cell types -
four small, spherical glands that are embedded in the posterior surface of the thyroid gland
chief cell (major), oxyphil cell - chief cell
- major cell type, arranged in cords or clumps; small polyhedron-shaped cells with secretory granules visible only with electron microscope; secrete PTH which increases blood calcium levels, primarily by increasing osteoclast activity
- oxyphil cell
- large cell may appear singly or in clumps; heterochromatic nucleus and abundant eosinophilic cytoplasm, due to numerous mitochondria; no secretory granules (fxn unknown)
-
adrenal glands
- general definition
- subdivisions / embryological origin -
paired glands, each located at the superior pole of a kidney
cortex -- derived from mesoderm and constitutes the major steroid-producing center
medulla -- derived from neural crest and is the major source of epinephrine and norepinephrine neurohormones - adrenal cortex: list four features of these steroid-secreting cells
-
(1) abundant smooth ER
(2) mitochondria with tubular cristae in the zona fasciculata and the zona reticularis; shelf-like cristae in the zona glomerulosa
(3) numerous lipid droplets filled with cholesterol, precursor for steroid hormones
(4) secretion is by diffusion, with no hormone storage - list and describe the three zones of the adrenal cortex
-
(1) Zona glomerulosa
- located immediately beneath the capsule; cells appear as round clusters; secretes mineral corticoids (e.g. aldosterone)
(2) Zona fasiculata
- middle layer, largest corticle zone; cells arranged in rows perpendicular to the capsule with alternating wide-diamter, fenestrated capillaries; secretes glucocorticoids and androgens
(3) Zona reticularis
- occupies deepest layer of the cortex; cells arranged as anastomosing cord; same secretions as zona fasciculata - adrenal medulla
-
composed of chromaffin cells (modified adrenergic neurons without axons or dendrites; represent symp ganglion cells; polyhedral cells containing abundant dense-core secretory granules)
synth and release Epi and NE -
pineal gland:
- general definition - conical-shaped gland, 5-8 mm in length and 3-5 mm in width; develops from the roof of the diencephalon and remains attached by a short pineal stalk
-
pineal gland:
- surrounded by? - a capsule composed of pia mater
-
pineal gland:
- cell types? which is major? - pinealocytes (major), interstitial cells
- pineal gland: pinealocytes
- modified neurons; euchromatic Nu, spherical to ovoid, with a prominent nucleolus; processes end in association with capillaries, secretes melatonin
- pineal gland: interstial cells
- Nu elongated and more heterochromatic than that of pinealocytes; long processes with intermediate filaments; located among groups of pinealocytes and in the connective tissue septae
- pineal gland: corpora araneacea
-
brain sand
globular, basophilic accumulations of calcium phosphates and carbonates in the interstitial space - pineal gland: secretion
-
major secretion is melatonin
secreted in dark, inhibited in light
retinal stimulation by light is relayed to the pineal via symp innerv from the superior cervical ganglion - what are the four fxns of the testis?
-
(1) produce sperm
(2) produce male sex hormones
(3) produce seminal fluid (semen)
(4) propel sperm and seminal fluid to exterior - testis serves both exocrine and endocrine fxn?
-
exocrine - sperm
endocrine - testosterone production - tunica albuginea
- a layer of dense CT beneath the tunica vaginalis, encapsulating the seminiferous tubules
- blood-testis barrier
-
occluding jxns that unite the processes of adjacent Sertoli cells, dividing the seminiferous epithelium into:
(1) basal compartment
(2) adluminal compartment - 7 fxns of supporting cells of sertoli
-
(1) mediate exchange of nutrients to germ cells
(2) form blood-testis barrier
(3) breakdown excess spermatid cytoplasm
(4) produce testicular fluid
(5) secrete androgen-binding protein that binds to and concentrates testosterone in the seminiferous epithelium
(6) produce inhibin which inhibits the secretion of FSH from the adenohypophysis
(7) orchestrate movement/cytodifferentiation of germ cells - 5 steps of cytodifferentiation
-
(1) intercellular bridges break down
(2) nucleus condenses and elongates
(3) acrosome forms
(4) flagellium forms
(5) excess cytoplasm is shed - 4 Stages of Spermatogenesis
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(1) Spermatocytogenesis -- mitotic divisions of spermatogonia (diploid) to form primary spermatocytes (diploid); cytokinesis is incomplete
(2) Meoisis -- I (form secondary spermatocytes, haploid), II (form spermatids, haploid)
(3) Spermiogenesis -- cytodifferentiation of spermatids into spermatozoa
(4) Spermiation -- release of mature sperm into lumen of seminiferous tubule - list two pathologies associated with the prostate
-
(1) benign prostatic hypertrophy
- hyperplasia of the glands immediately surrounding the urethra
(2) prostate cancer - what are the 9 fxns of the female reproductive system?
-
(1) produce female germ cells (ova)
(2) produce female sex hormones, estrogen and progesterone
(3) transport female germ cells, sperm, and conceptus
(4) provide site of fertilization
(5) house and nourish conceptus during pregnancy
(6) maintain pregnancy
(7) expel fetus at parturition
(8) form birth canal
(9) receives sperm - corpus albicans
- degenerating corpus luteum
- 4 stages of oogenesis
-
(1) oogonia in the fetal ovary divide mitotically to form diploid, primary oocytes that are located in primordial follicles
(2) primary oocytes immediately begin the first meoitic division, that arrests in prophase
(3) a secondary oocyte is formed during the day preceding ovulation in each ovarian cycle. A primary oocyte in a Graafian follicle completes meiosis I to from a haploid, secondary oocyte. This secondary oocyte begins meiosis II but arrests in metaphase; this is the oocyte that is ovulated
(4) an ovum, a mature, haploid germ cell, is formed in the oviduct (completion of meiosis II) only after fertilization occurs - cycle of ovary
-
(1) follicular phase (1-13) -- follicles are differentiating and secreting estrogen; follicles begin to develop while menstruation is occuring
(2) ovulation (14) -- graafian follicle ruptures, releasing secondary oocyte
(3) luteal phase (15-28) -- corpus luteum is the functional ovarian structure, secreting progesterone and estrogen. Hormone secretion diminishes after day 26 - Oviduct segments:
-
(1) infundibulum -- funnel-shaped free end with fimbria which embrace the ovary
(2) ampulla -- thin walled, lateral 2/3; fertilization occurs here near the jxn with isthmus
(3) isthmus -- thicker walled, narrower, medial 1/3
(4) intramural -- within uterine wall; lumen is continuous with uterine lumen - Uterus subdivisions:
-
(1) fundus -- domed portion above entrance of oviducts
(2) corpus or body -- major portion
(3) isthmus -- constricted portion at jxn of cervix and body
(4) cervix -- located above and within the vagina - colostrum
- secreted for the first few days after birth; protein rich with a high antibody content
- milk
- secretory product released after the colostrum phase; milk has a high lipid content compared with colostrum and also contains protein, carbs, and antibodies
- 4 Placental fxns
-
(1) provides exchange of respiratory gases between maternal and fetal circulations
(2) provides nutrients for and removes wastes from fetus
(3) secretes hormones
(4) transports some macromolecular materials - trophoblast cells
- form the peripheral rim of the fluid-filled blastocyst cavity; these cells will form the fetal portion of the placenta
- inner cell mass
- cluster of cells inside the trophoblast at one pole of the blastocyst; these cells will develop into the embryo
- chorion
- composed of extra-embryonic fetal CT and two cell layers derived from the trophoblast, called the cytotrophoblast and the syncytiotrophoblast
-
placentral interhemal membrane
- definition and parts -
placentral interhemal membrane -- separates the maternal and fetal blood supplies, which normally do not mix
consists of:
(1) capillary endothelial cell (of villus) and its basement membrane
(2) fetal CT of villus
(3) cytotrophoblast and its basement membrane
(4) syncytiotrophoblast - three subdivisions of decidua
-
(1) decidua basalis -- underlies the implanted conceptus (beneath trophoblastic shell), forming the maternal portion of the functional placenta
(2) decidua capsularis -- covers the luminal surface of the conceptus, seperating it from the uterine lumen; will eventually fuse with decidua parietalis of the opposite side, obliterating the uterine lumen
(3) decidua parietalis -- lines the remainder of the uterus - rete testis lined with
- simple cuboidal epithelium
- efferent ducts lined with
-
simple columnar / cuboidal epithelium with cilia
lysosomal granules in epithelium - duct of the epididymis lined with
-
pseudostratified columnar epithelium with stereocilia
smooth muscle surrounding duct of epididymis - ductus deferens lined with
- pseudostratified columnar epithelium with stereocilia
- what is the most important diagnostic feature of the ductus deferens?
-
muscularis externa:
inner & outer longitudinal layers
middle circular layer