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Endo Repro > Endo Histo > Flashcards

Endo Histo Flashcards

1
Q

Paracrine signaling

A

Short-distance communication between cells via substances released, shed, or presented by cells to affect specific targets on other cells in the vicinity, within a tissue or organ [somatostatin in pancreatic and stomach d-cells]

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2
Q

Autocrine signaling

A

Substances are released by a cell and affect the cell of origin itself [interleukins, growth factors]

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3
Q

Juxtacrine signaling

A

Substances expressed/anchored to the cell membrane bind to receptors on adjacent cells [delta/notch signaling in the developing nervous system and immune system]

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4
Q

Endocrine signaling

A

Communication between cells involving substances released through interstitial space and carried by the vascular system

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5
Q

Hormones

A

Factors synthesized from amino acids, cholesterol or phospholipids that use endocrine routes to induce distal cellular changes through specific binding to receptors …non-endocrine signaling substances are called “factors”

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6
Q

Other types of signaling

A

synaptic, intracellular

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7
Q

Epithelial info about endocrine glands and organs

A

Epithelial/epitheloid

Lacks a free surface, embedded in connective tissue

Fenestrated capillaries and lymphatic capillaries surround secretory tissue

Hormones are released into interstitial space

DUCTLESS (vs. exocrine)

Secretory cells are organized in follicles, anastamosing cords, nests, or clusters

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8
Q

Hypothalamus

A

Hypothalamus is the central regulator of the endocrine system

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9
Q

Nuclei of the hypothalamus

A

11 ‘major’ nuclei of the hypothalamus with diverse functions, release diverse substances

For the neuroendocrine system, we care about the PV (paraventricular) and SO (supraoptic) nuclei, in particular

Some release neurotransmitters

Some release neurohormones

Both can have indirect or direct effects on glands

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10
Q

Two major types of neurohormones in the neuroendocrine system

A

Releasing/Inhibiting Hormones

Direct hormones

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11
Q

Hypothalamic Connection to the pituitary gland

A

Below the hypothalamus is neural tissue transitioning into the pituitary gland, called the median eminence, which is surrounded by capillary beds

The median eminence lacks a blood-brain barrier

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12
Q

Hypothalamus network with pituitary

A

Hypothalamus: median eminence: infundibulum (posterior pituitary)

Below infundibulum (“pituitary stalk” )is pars nervosa

Axons from both the PV Hypothalamus and SO Hypothalamus project through infundibulum into pars nervosa, release oxytocin or vasopressin into pars nervosa

Called the neurohypophysis

Below the median emenince is hypothalamo-hypophyseal portal system

Arteries from internal carotid artery varry neurohormones (releasing and inhibiting) to anterior pituitary, called adenohypophysis

Pars tuberalis- Mostly vascularized area, wraps around infundibulum

Pars intermedia- Transitional area

Pars distalis

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13
Q

Posterior pituitary embryological origins

A

Posterior Pituitary from neuroectoderm, extension of the same structure of developing hypothalamus

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14
Q

Anterior pituitary embryological origins

A

Anterior Pituitary from oral ectoderm, develops from Rathke’s Pouch

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15
Q

Pituitary gland tissue and location

A

Pituitary gland is heterogenuous, pea-sized gland sitting in the sella turcica of the sphenoid bone

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16
Q

What’s in the anterior pitutitary (histological)

A

Cell bodies of secretory cells

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17
Q

What’s in the posterior pituitary

A

Axon terminals of neurons

if you see cell bodies, they’re most likely specialized glial cells: pituicytes

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18
Q

Two major components of neurohypophysis (posterior):

A

(hypophysis = pituitary gland)

Axons of hypothalamic neurons from PV and SO

Pituicytes

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19
Q

Herring Bodies

A

Unmyelinated Axons have dilations called “Herring Bodies”

Release either Vasopressin (AVP/ADH) or Oxytocin (+others) from neuroscretory vesicles

Along with neurophysin and ATP

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20
Q

Pituicytes

A

Pituicytes = astrocytes of the pituitary gland Will stain with GFAP - marker for astrocytes [*Think about immunocytochemistry]

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21
Q

Oxytocin

A

Milk letdown reflex

Uterine smooth muscle contraction during orgasm, menstruation and parturition Oxytocin injections

22
Q

Vasopressin (ADH)

A

Increase water permeability in kidneys

Diabetes insipidus

Central Nephrogenic

23
Q

Adenohypophysis histology

A

Cells are in clumps or cords with sinusoidal spaces

Classical staining of acidophils (lighter), basophils (purple/blue), and chromophobes (no stain)

Basic histology of the adenohypophysis tells relatively little compared to immunocytochemistry

Lactotrophs (PRL, VIP), somatotrophs (GH), corticotrophs (ACTH), gonadotrophs (FSH and LH), thyrotrophs (TSH)

Receptors for Releasing Hormones

Folliculo-stellate cells (supportive functions, might be stem cells)

The pars distalis has majority of the endocrine cells

24
Q

The other aspects of the adenohypophysis (pars intermedia and pars tuberalis)

A

The pars intermedia contains colloid-filled spaces and MSH

The pars tuberalis surrounds the infundibulum, mostly vascularized region of the pituitary

25
Q

Hormone categories of the adenohypophysis

A

somatotrophs, lactotrophs, gonadotrophs, thyrotrophs, coricotrophs

26
Q

somatotrophs

A

somatotropin (Growth hormone, GH), A

cidophil

major functions: stimulates growth in epiphysial plates of long bones via IGF (insulin growth factors) produced in the liver

27
Q

lactotrophs

A

Prolactin. acidophil, promotes milk secretion

28
Q

gonadotrophs

A

FSH and LH, basophilic

FSH promotes ovarian follicle development and estrogen secretion in women, spermatogenesis in men

LH promotes ovarian follicle maturation and progesterone secretion in women, interstitial cell androgen secretion in men

29
Q

Thyrotrophs

A

Thyrotropn (TSH), basophilic

Stimulates thyroid hormone synthesis, storage and liberation

30
Q

Corticotrophs

A

Adreno corticotropin (ACTH), Lipotropin (LPH), Basophilic

ACTH stimulates secretion of adrenal cortex hormones

LPH helps regulate lipid metabolism

31
Q

Kallmann syndrome

A

DSD “Differences in Sexual Development”

Hypogonadatropic

Hypogonadism

Delayed or absent puberty

Impaired sense of smell

Mutations in genes regulating migration of GnRH-containing neurons Also regulate migration of olfactory neurons

32
Q

Review the basic organization of the hypothalamic-pituitary system

A
33
Q

Pineal Gland- the other major neuroendocrine tissue source

A

•“Photo-neuroendocrine system”

–Retina, hypothalamus, pineal gland all derived from the same source (diencephalon).

–Neuroectoderm

  • Part of the epithalamus
  • Two major cell types:

–Pinealocytes (modified neurons)

•Release melatonin

–interstitial cells (glia)

  • Unmyelinated nerve axons from superior cervical ganglia
  • Brain sand in CT scans show “brain sand” or corpora arenacaea

–Calcium phosphate

–Midline of brain in CT

34
Q

neurons vs glial cells

A

neurons usually larger, rounder

35
Q

What does melatonin do?

A
  • There are 3 types of melatonin receptors (MT1-3)
  • It’s synthesis is inhibited by light

–Signals night-time to the body

  • In many animals, the day length coding determines lengths of reproductive cycles, affecting activity of GnRH neurons (not so in humans)
  • Not entirely necessary * for humans, although tumors = early onset puberty

Melatonin synthesis is regulated by the sympathetic nervous system. Pathway from hypothalamus to spinal cord to SCV back up to pineal gland

36
Q

Thyroid gland - Follicles (hormones stored in inactive form here)

A

•Follicular epithelium

–Surround the big colloid-containing follicles (thryoglobulin…precursor to the stuff released)

–Follicular cells (thyrocytes)

•Easier to identify…going to be darker (more basophilic) and make contact with follicles themselves. Make T3 and T4. These cells transport iodide.

–Parafollicular cells (calcitonin)

  • In light microscopy, actually paler staining, solitary, not abutting the follicles
  • Supposed to oppose the actions of PTH
37
Q

T cells vs C cells

A

T cells come into direct contact with the follicle, C cells usually have some layers in between.

38
Q

Steps of T3 and T4 production and transport

A
  • Production of thyroglobulin
  • Uptake of iodide from blood
  • Iodination of tyrosyl residues in thryoglobulin in the colloid
  • Formation of T3 and T4
  • Endocytosis of iodinated thyroglobulin by thryrocytes

Secretion of T4 and T3

39
Q

Parathyroid gland

A
  • Gross structure: 2 pairs of small ovoid, superior and inferior (in connective tissue, in posterior surface of thyroid gland)
  • Septa from connective tissue divide into lobules

–Fat cells in connective tissue of adults, easier to see

•Blood from inferior thyroid arteries—lots of fenestrated capillaries and lymphatic capillaries

40
Q

Parathyroid gland Main Actors: Principal/Chief cells

A
  • More of the parenchyma, tangled curvilinear cords of chief cells
  • Regulate synthesis, storage and secretion of PTH
  • Small, polygonal, centrally located nucleus
  • Acidophilic
  • Replicate when they are stimulated by changes in blood calcium levels
41
Q

Oxyphil cells: the other type of parathyroid cell

A
  • Not secretory, fewer
  • More rounded, larger than principal cells, distinctly acidophilic cytoplasm
  • Derived from Chief cells
  • Found increases in CKD, tumors
  • Possible paracrine action on chief cells
42
Q

Adrenal Glands: gross anatomy

A

•

–Glands are both embedded in perirenal fat superior t okidney

–Covered in a thick connective tissue capsule

–2 divisions of secretory tissue: medulla (catecholamine-secreting) and cortex (steroid-secreting)

43
Q

adrenal glands: blood supply

A

–Capsular arteries supply capsule,

–Fenestrated cortical sinusoidal capillaries supply cortex and drain into fenestrated medullary capillary sinusoids,

–Medullary arterioles that traverse the cortex, travel within the trabeculae and bring arterial blood to the medullary capillary sinusoids

•

–The medulla has a dual blood supply, arterial blood from the medullary arterioles and venous blood from the cortex

•

–Lymphatic vessels in the capsule around larger blood vessels and in the medulla,

•

44
Q

Adrenal medulla

A
  • Pale staining, epitheloid (from neural crest) chromaffin cells.
  • Will aslo see sinusoidal blood capillaries , connective tissue, and nerves (stroma)
  • Chromaffin cells are modified neurons (neural crest derivatives)
45
Q

Chromaffin cells

A

–Glucocorticoids released by the adrenal cortex are thought to have inhibited axonal growth from the chromaffin cells

–Chromogranins present

–Chromaffin cells organized in ovoid clusters

–Presynaptic, myelinated sympathetic nerve fibers synapse on chromaffin cells.

–Chromaffin cells secrete either norepinephrine or epinephrine (80:20 ratio) [“catecholamines”]

  • Cell type determined by proximity to cortex
  • Cell type determined by type of dense core vesicle
46
Q

Pheochromocytoma

A
  • Excessive catecholamines produced
  • Symptoms of over-active sympathetic nervous system
  • Large, loose clusters of chromaffin cells enveloped by thin, vascular channels (zellballen)
47
Q

Adrenal Cortex: zona glomerulosa

A

–cells are closely packed in ovoid clusters and curved columns continuous with the cellular cords in the fasciculata.

–Small and columnar or pyramidal. Spherical nuclei.

–Rich network of fenestrated sinusoidal capillaries around each cluster. Lots of smooth ER (think about the lipid nature…)

–Secretes aldosterone, which controls BP (a mineralocorticoid in fluid and electrolyte balance).

–Product of cholesterol, synthesis controlled by actions of angiotensin II

–Aldosterone synthase is only found in glomerulosa cells.

48
Q

Adrenal Cortex: Zona fasciculata

A

–Most of cortical volume

–large and polyhedral cells

–arranged in long, straight cords, one or two cells thick and separated by sinuosoidal capillaries.

–Spherical nucleus. May see binucleate cells.

–Developed sEr (because steroid secreting)

–Produce glucocorticoids and gonadocorticoids. Cortisol acts across body and brain.

–“HPA-axis” From ACTH

•

49
Q

Adrenal Cortex: Zona Reticularis

A

–Smaller cells than in fasciculata. Nuclei are more deeply stained.

–Anastamosing cords separated by fenestrated capillaries. Large lipofuscin.

–Mostly secrete gonadocorticoids DHEA, DHEAS, and androstenedione.

50
Q

lipofuscin

A

brownish stain in the middle of a cell that indicates it is older…

51
Q

Congenital Adrenal hyperplasia

A
  • Collection of genetic conditions, usually causes DSD
  • Androgenizing phenotype
  • May lack aldosterone
  • May lack cortisol

What would an XY male with CAH look like? Very male. Lots of hair, but also lots of problems and will die with messed up levels of aldosterone/ cortisol etc.

An XX female would have a “psuedopenis,” large clitoris

What would an XY female with CAH look like?

52
Q

Endocrine Pancreas

A

•Pancreas is both exocrine and endocrine

–Islets of Langerhans scattered throughout exocrine tissue, mostly in tail of pancreas

–Islet cells secrete: glucagon, insulin, or somatostatin

–α, β or δ-cells, respectively

Endo Repro (12 decks)

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