202 ES - Histology Flashcards by Ina Vong

What are the 3 classes of hormones?

Steroids
Small peptides, polypeptides & proteins
Amino acids & arachidonic acid analogs & derivatives

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3 modes of hormonal action

Endocrine control
Paracrine control
Autocrine control

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Endocrine control

A cell targets a distant cell through the bloodstream

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Paracrine control

A cell targets nearby cell

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Autocrine control

A cell targets itself

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Mechanism of hormone action on cell surface receptors

Interact with hormones of catecholamines: second messengers

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Mechanism of hormone action on intracellular receptors

Steroids & thyroid hormones: receptors are in nucleus, bind to DNA & affect gene expression

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General functions of endocrine system

Secretes hormones
Communicate w peripheral cells & organs to maintain homeostasis & regulate development and growth
Metabolic rate
Blood calcium level
"fight or flight"
Reproductive function
Water reabsorption
Milk secretion
Social bonding
Love

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Endocrine glands & hormonal target tissues (4)

Hypothalamo-hypophyseal (pituitary gland)
Hypothalamus-pituitary gland-adrenal glands
Hypothalamus-pituitary gland-thyroid & parathyroid glands; pancreas & pineal gland
Hypothalamus-pituitary gland-gonads (ovary & testis)

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Median eminence

Region of hypothalamus, where hormones are relased

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Infundibulum

Pituitary stalk, infundibular stalk

Tube connecting hypothalamus to pituitary

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3 parts of adenohypophysis (anterior lobe of pituitary gland)

Pars distalis
Pars tuberalis
Pars intermedia

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4 parts of neurohypophysis (posterior lobe of pituitary gland)

Pars nervosa
Infundibulum
Median eminence
Infundibular stem

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2 types of cells found in pars distalis

Chromophils (further divided into acidophil & basophil)

Chromophobes

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What does acidophil secrete?

Prolactin (lactogenic hormone)

GH (growth hormone)

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What does basophil secrete?

LH & FSH
TSH (thyroid stimulating hormone)
ACTH

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What are chromophobes?

Minimal or no hormonal content

May be acidophils or basophils that have degranulated and thereby are depleted of hormone

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Releasing hormones of hypothalamus

Thyrotropin-releasing hormone (TRH)
Corticotropin-releasing hormone (CRH)
Gonadotropin-releasing hormone (GnRH)
Growth hormone-releasing hormone (GHRH)

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Inhibiting hormones of hypothalamus

Somatostatin

Dopamine

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Deficiency of vasopressin or loss of vasopressin (ADH) action results in?

Diabetes insipidus

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Which hormone controls water resorption in collecting ducts in kidney?

Vasopressin (ADH)

↑ ADH ↑ water reabsorption

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ADH pathway in water resorption

Hypothalamus produce ADH → stored in posterior lobe of pituitary gland → excreted to circulation → water reabsorption from distal and collecting tubules → urine is concentrated

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Oxytocin pathway of milk ejection

Positive feedback:
Oxytocin produces in hypothalamus → stored in posterior pituitary → released to mammary gland
→ baby sucks on nipples → stimulate sensory receptors around nipple → reaches hypothalamus & more oxytocin released

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Where is adrenal cortex derived from?

Mesodermal epithelium

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Blood supply of adrenal glands

Superior suprarenal arteries Middle suprarenal arteries Inferior suprarenal arteries

Zona glomerulosa secretions & function

Mineralocorticoids: aldosterone, deoxycortocosterone Function: fluid & ekectrolyte balance

Zona fasiculata & zona reticularis secretion & function

Gluococorticoids: cortisone, cortisol, corticosterone Function: - metabolism of carbohydrates, proteins & fats - anti-inflammatory & anti-immune

Adrenal medulla secretion

Catecholamine

Hypothalamic-pituitary-adrenal (HPA axis) function

Regulate the stress response

How does Hypothalamic-pituitary-adrenal (HPA) axis work?

Stress → hypothalamus release corticotropin-releasing hormone (CRH) → CRH signals the pituitary gland to secrete adrenocorticotropic hormone (ACTH) to the bloodstream → ACTH reaches adrenal glands → release cortisol from the adrenal cortex

Function of cortisol

Increased cortisol, increased availability of glucose for "fight or flight" Cortisol will negatively feedback to inhibit both the hypothalamus and the pituitary gland → shutting off the stress response

Pheochromocytoma

A tumor that produces excessive amounts of catecholamine

Function of thyroid gland

To store & release thyroid hormone (TH) - regulates mitochondrial biogenesis & metabolic rate

2 types of cell found in parenchyma of thyroid gland

``` Follicular cells (principle cells) Parafollicular cells (C cells) ```

Function of follicular cells (principle cells)

Produce T3 & T4

Function of parafollicular cells (C cells)

Secrete calcitonin - lowers blood calcium

Thyroxine (T4) & triiodothyronine (T3) function

Regulate cell and tissue basal metabolism and heat production and influence body growth and development.

T3 & T4 regulation

Regulated by TSH released from the anterior lobe of the pituitary gland.

How does calcitonin lower blood calcium level?

Suppressing resorptive action of osteoclasts and promotes calcium deposition in bones by increasing the rate of osteoid calcification.

Goiter

Chronic enlargement of thyroid

Colloid goiter (endemic goiter)

Iodine-deficiency goiter

Hashimoto's thyroiditis

Autoimmune thyroiditis Hypothyroidism → stimulate release of excessive amounts of TSH → hypertrophy of the thyroid

Exophthalmic goiter (Graves's disease)

Hyperthyroidism Abnormal IgG bind to TSH receptors → increase thyroid secretion

High TSH levels

Hypothyroidism Not enough thyroid hormones

Low TSH levels

Hyperthyroidism Too much thyroid hormones

Exophthalmos

Pop-eyed | Seen in exophthalmic goiter (Graves's disease)

2 types of cells in parathyroid gland

Principal (chief) cells | Oxyphil cells

Principal (chief) cells

Secrete parathyroid hormone (PTH) - regulated by blood calcium levels

Oxyphil cells

Not known to have a secretory role | Mitochondria almost fill the cell

Parathyroid hormone (PTH) function

Stimulates bone resorption | Increase blood calcium level

Calcium homeostasis is regulated by?

PTH & calcitonin

Calcitonin

Inhibits bone resorption

Bone resorption

Osteoclasts break down the tissue in bones and release the minerals → transfer of calcium from bone tissue to the blood

2 types of cells in pineal glands

Pinealocytes (chief cells) | Interstitial (glial) cells

Pineal gland function

Produces melatonin that controls the circadian rhythms | Reproductive function by inhibiting steroidogenic activity of gonads

Calcified concretions in pineal glands

Corpora arenacea | aka. Brain sand

Endocrine pancreas function

Regulate blood glucose level w insulin & glucagon

Islets of Langerhans

Pancreatic cells secreting insulin & glucagon

5 cell types of pancreas & their secretion

``` A (alpha) cells - glucagon B (beta) - insulin D (delta) - somatostatin PP (pancreatic polypeptide) cell - PP Epsilon cell - ghrelin ```

How are the A cells & B cells arranged in the pancreatic islet?

B cells are in the core | A cells are the surronding

What cells are found in the ovary? & their secretion?

Follicular & theca cells | Secrete estrogen

What cells are found in the testis? & their secretion?

Interstitial cell of Leydig | Testosterone

Which type of DM has a higher genetic linkage?

Type 2

Metabolic Consequences of DM

Insulin production, secretion, action defect in DM Hyperglycemia Dyslipidemia