General Flashcards
(69 cards)
1
Q
Thyroid hormone
synthesis
function
A
Synthesized by addition of iodine to tyrosine
• Critical to brain development
2
Q
Thyroid hormone
regulate
deficiency leads to?
A
Regulate
- • metabolic rate
- • circulation
- • bone turnover
• Deficiency:
- • Slow heart,
- brain,
- metabolism
3
Q
Hypothalamus
What does it produce?
A
Thyrotropin releasing hormone
TRH
4
Q
Pituitary
What does it produce?
A
Thyroid stimulating hormone
TSH
5
Q
THyroid
What does it produce?
A
- Thyroxine - T4
- Triiodothyronine - T3
6
Q
What happens in the Periphery that the hormones can effect?
A
Pulse
Basal Metabolic Rate
7
Q
Hypothyroidism
What are primary, secondary and tertiary deficiencies?
where does hormone resistance occur?
A
Issue with the organ is:
- Thyroid
- Primary
- Pituitary
- Secondary
- Hypothalamus
- Tertiary
Resistance - can occur in the periphery in response to thyroid hormone which can lead to defieciency linked diseases
8
Q
Anatomy of the Pituitary and Hypothalamus
A
Pituitary:
- sits at base of brain
- in a pocket (pituitary fossa) in the Sphenoid bone
- bony cavity - sella turcica (turkish saddle)
Hypothalamus - sits just above the pituitary gland
9
Q
Anterior pituitary
A
aka Adenohypophysis
hypothalamic hormones travel to it via blood vessels
10
Q
Posterior pituitary
A
Aka Neurohypophysis
hypothalamic hormones stimulated via the neural fibres
Produce Vasopressin/ADH
11
Q
What lies lateral to the pituitary
A
Cavernous sinus
pituitary surgeru can cause damage to surrounding structures
e.g nerves, ICA etc
12
Q
What can pituitary tumours damage?
A
Optic nerve
can cause vision problems
13
Q
Anterior pituitary hormones
A
-
TSH -> thyroid -> thyroxine
- • influences metabolic rate
-
ACTH -> adrenals -> cortisol
- • influences stress response
-
GH -> liver -> IGF-1
- • vertical growth (in children), bone mass, metabolism
-
LH/FSH -> gonads -> testo/estradiol
- • sex hormones, sperm and ova
- PRL (prolactin) -> breast -> lactation
14
Q
Excess GH
causes?
A
Acromegaly
15
Q
Excess ACTH
causes?
A
Cushing’s
16
Q
Excess PRL (prolactin)
causes
A
Galactorroea
Amenorrhoea
17
Q
Excess TSH
causes
(i.e by a TSHoma etc)
A
Thyrotoxicosis
18
Q
Peptide/Protein hormone cell
A
– Lots of rER
– Golgi
– Secretory vesicles
19
Q
Steroid secreting cells
A
– Lots of smooth ER
– Abundant mitochondria
– Lipid droplets (precursor for making steroid hormones)
20
Q
Pititary Anatomy
A
- rounded body, about 1 cm dia.
- connected to floor of III ventricle by the infundibulum (pituitary stalk), just posterior to the optic chiasma
- lies in a depression in the body of the sphenoid – pituitary (hypophyseal) fossa – also called the sella turcica
21
Q
Pituitary fossa
A
• Pituitary fossa is lined by dura and covered over by a covered over by a sheet of dura (diaphragma sellae), pierced by the pituitary stalk
22
Q
• Adenohypophysis (Anterior pituitary)
more glandular
A
– pars distalis
– pars tuberalis (surrounds the stalk)
– pars intermedia
extension of the hypothalamus
23
Q
Neurohypophysis (Posterior pituitary)
A
– pars nervosa
– infundibulum (neural stalk) - continutation of the brain tissue/neural tissue
24
Q
Pituitary gland
Development
A
Adenohypophysis
- an upgrowth of ectoderm/endoderm from the embryonic oral cavity (Rathke’s Pouch).
Neurohypophysis
- downgrowth from floor of the diencephalon.
25
POsterior pit.
* Consists of axons of modified neurones, supported by a population of glial-like cells, called ***pituicytes***.
* Cell bodies of these neurones **lie in the supraoptic and paraventricular nuclei of the hypothalamus.**
26
Post pit hormones
• “Transmitters” are the hormones:
**antidiuretic hormone (ADH, vasopressin)**
* increases water retention in kidney.
* raises blood pressure by contracting vascular smooth muscle cells (at high concentrations) smooth muscle cells (at high concentrations).
**oxytocin**
• contraction of smooth muscle cells, esp. of uterus during childbirth; and myoepithelial cells of mammary gland during lactation.
27
ADH and oxytocin
ADH and oxytocin are peptides (9 aa each, 2 different)
* made in cell bodies of neurones (in hypothalamus) as a larger protein, subsequently cleaved to yield the hormone and a binding protein (neurophysin).
* transported down axons to terminals
* released from terminals into fenestrated capillaries on stimulation of the cell bodies in the hypothalamus.
* accumulations of hormone within the axons exist, called Herring bodies
28
Ant Pit
Pars distalis
Pars distalis
• Cords of cuboidal/polygonal epithelial secretory cells clustered around large, fenestrated sinusoids. • Traditionally classified into:
– Acidophils
– Basophils
– Chromophobes
29
Pars Distalis
• **Acidophils**
## Footnote
– *Somatotrophs* Growth Hormone
– *Mammotrophs* Prolactin
**• Basophils**
– *Thyrotrophs* Thyroid Stim. Hormone
– *Corticotrophs* Adrenocorticotrophic hormone
– *Gonadotrophs* Follicle stim. Hormone Luteinizing hormone
**• Chromophobes**
– either reserve cells or resting cells that have lost their secretory granules
30
Pars Tuberalis
• Thin layer of cuboidal cells, mostly gonadotrophs.
31
Pars intermedia
• Cells secrete
**Melanocyte stimulating hormone** – increases skin pigmentation, but physiological role in man is uncertain.
32
Stimulating hypothalamic hormones
* Thyrotropin releasing hormone (TRH)
* Gonadotropin releasing hormone (GnRH)
* Growth hormone releasing hormone (GRH)
* Corticotropin releasing hormone (CRH)
33
Inhibiting hypothalamic hormones
* Somatostatin (blocks GH and TSH release)
* Dopamine (blocks prolactin release)
34
Reasons for a portal system
1. Need less releasing hormone
2. More immediate response
3. Can use the same hormone again elsewhere for other purposes
e. g. somatostatin from Islets of Langerhans blocks release of insulin and glucagon.
35
Thyroid
Anatomy
* 2 pear-shaped lateral lobes connected by a midline isthmus
* intimately related to the trachea
* isthmus lies at level of 2nd-4th tracheal rings
* isthmus may be joined to the hyoid bone by a fibrous cord, a remnant of the embryological thyroglossal duct
36
Throid
development
• Arises from a diverticulum in floor of the primitive pharynx just caudal to the site of the future tongue
## Footnote
– thyroglossal duct
– opens at base of tongue as the foramen caecum
– connection to pharynx eventually lost, isolating the gland
37
Thyroid cell organization
Thyroid epithelial cells are organized into follicles.
**– secrete thyroglobulin** (large glycoprotein, mw 660Kd)
– accumulates in the follicles as “colloid”
38
Thyroid follicular cells
Thyroid follicular cells take up iodide
– oxidized to Iodine
– covalently attached to the tyrosines of thyroglobulin within the lumen of the follicle
* On stimulation by TSH (from the anterior p u a y) ituitary)
* follicular cells endocytose the iodinated thyroglobulin
* break it down in lysosomes
* release the iodinated tyrosine derivatives as tetra- iodothyronine (thyroxine) (T4) or triiodothyronine (T3)
39
C cells/Parafollicular cells
* scattered cells found within the follicular epithelium or as clusters between the follicles.
* larger, more rounded than the follicle cells
**• secrete calcitonin (inhibits Ca++ mobilization**)
• neural crest-derived - migrate to thyroid during development.
40
Parathyroid gland
Anatomy
* 2 pairs of parathyroid glands, each about the size of a pea
* Usually found on or embedded in the posterior border of the lateral lobes of the thyroid gland, but position is somewhat variable (esp. inferior parathyroids)
* No functional significance in the association between thyroid and parathyroid glands
41
Parathyroid gland
Cellular organisation
Densely-packed, **small Chief (or principal) cells** arranged in irregular cords aro nd blood around blood vessels
. – **secrete parathyroid hormone (parathormone)**
– stimulates calcium mobilization.
42
Adrenal glands
Anatomy
* **Pyramidal (right) or crescentshaped (left) bodies in contact with the upper poles of the poles of the kidneys**
* Separated from kidneys by connective tissue but surrounded by the renal fascia.
43
Development of the adrenal glands
The adrenal glands have 2 distinct parts with different origins:
## Footnote
• **Cortex**
– derived from the coelomic epithelium (mesothelium) lining the posterior abdominal wall
• **Medulla**
– derived from an adjacent sympathetic ganglion
44
Adrenal cortex
• Cells secrete steroids
## Footnote
– have lots of SER and lipid droplets (containing cholesterol) so appear pale and "frothy" in histological sections.
• Cells are organized into 3 zones:-
**– Zona glomerulosa (**outermost)
**– Zona fasciculata**
**– Zona reticularis**
45
Zona Glomerulosa
| (outer part of cortex)
* cells arranged in rounded clusters, surrounded by capillaries
* **secrete mineralocorticoids – mainly aldosterone (95%)**
* Target : Na+ retention in kidney – (distal convoluted tubule)
* *regulated by renin/anigiotensin system*
46
Zona Fasciculata
| (bulk of cortex)
* cells arranged in straight cords, running radially
* **secrete glucocorticoids – mainly cortisol (95%)**
* Target : glucose, lipid and protein metabolism
*• secretion regulated by ACTH*
47
Zona Recticularis
• cells arranged in irregular cords
**• secrete some *glucocorticoids* and small quantities of *sex steroids (mostly weak androgens)***
• functionally insignificant (?)
48
Adrenal Medulla
* modified sympathetic ganglion
* large, polyhedral cells arranged in cells arranged in clumps or cords
* resemble “axon-less” ganglion cells
*(cholinergic) preganglionic sympathetic input from the greater and lesser splanchnic nerves, via the coeliac ganglion.*
* on stimulation secrete on stimulation, secrete catecholamines catecholamines directly into the blood
* 80% of the cells secrete adrenaline (epinephrine); the rest, noradrenalin (norepinephrine)
49
what is the high conc of glucocorticosteroird from the cortex needed for?
needed to induce the enzyme responsible for converting noradrenalin to adrenalin.
50
Islets of Langerhans
* Small, rounded clusters of cells, 100-200 µm dia., embedded within the exocrine pancreas
* The cells are smaller and more-lightly stained than the exocrine cells, and arranged in irregular cords around capillaries
51
Cells in the Islets of Langerhans
**• A or cells** (~20%) secrete *glucagon*
**• B or cells** (~70%) secrete *insulin*
• **D or cells** (5-10%) secrete *somatostatin*
**• F or PP cells** (1-2%) secrete *pancreatic polypeptide*
• Other, minor cell types secrete vasoactiveintestinal peptide (VIP), substance P, motilin, serotonin, etc.
52
Steroid Hormone
*made from cholesterol*
* affect water & electrolyte balance
* mineralocorticoid - **aldosterone**
* affect carbohydrate & protein metabolism
* glucocorticoid - **cortisol**
* sexual characteristics
* sex steroids - **oestrogen; progesterone; testosterone**
53
Adrenal cortex
Hormones
* aldosterone,
* cortisol,
* androgens
54
Adrenal medulla
Hormones
adrenaline,
noradrenaline
55
Anterior Pituitary
(Endocrine cells)
hormones
* ACTH,
* GH,
* prolactin,
* FSH,
* LH,
* TSH
56
Hypothalamus/ Median Eminence
* TRH,
* CRH,
* GHRH,
* GnRH,
* somatostatin
* Inhibits Growth Hormone release
* controls both Insulin and Glucagon levels
* dopamine
* Inhibits Prolactin release
57
Ovary
Hormones
oestrogen,
progesterone
58
Pancreas
Hormones
glucagon,
insulin,
somatostatin
59
Parathyroid
hormones
parathyroid hormone (PTH)
60
Posterior Pituitary
(neural cells)
hormones
vasopressin (ADH),
oxytocin
61
Testes
hormones
testosterone
62
Thyroid
Hormones
calcitonin,
tri-iodothyronine (T3 ),
thyroxine (T4 )
63
Catechloamines
Multi-enzyme biosynthesis
Circulate in free form
stored in SECRETORY GRANULE or VESICLE (in neurons)
largely hydrophilic do not associate with plasma protein
64
Thryoid Hormones
Formed within thyroglobulin
Circulate mainly in bound form
stored in colloid as part of thyroglobulin
lipophilic
highly bound to plasma proteins
65
Proteins/Peptides
Rough endoplasmic reticulum
Peptides as precursor molecules
Circulate largely in free form
stored in SECRETORY GRANULE
both released by EXOCYTOSIS
triggered by Ca2+ contents released and granule recycled
largely hydrophilic do not associate with plasma protein
66
Steroid Hormones
Smooth endoplasmic reticulum
Formed form chlolesterol, multi-enzyme biosynthesis Circulate mainly in bound form
not stored, made from cholesterol stored in lipid droplets biosynthesis involves mitochondria & smooth endoplasmic reticulum
release not well understood
lipophilic highly bound to plasma proteins
67
Thyroxine T4
binding in plasma
**Active:**
* 0.04% free
**Inactive:**
* 70% bound to *thyroxine binding globulin (TBG)*
* 20% bound to *pre-albumin*
* 10% bound to *albumin*
68
Testosterone
binding in plasma
**Active:**
* 2% free
**Inactive**:
* 3% bound to *corticosteroid binding globulin*
* 60% bound to *sex hormone binding globulin*
* 35% bound to *albumin*
69
Assessment of hormone levels?
Via
* bioassay
* Radioimmunoassay (RIA)
* Enzyme-linked immunoabsorbant assay (ELISA)
RIA and ELISA are the most commonly used
