Lec3 - Nuts and Bolts of the Endocrine System Flashcards
(112 cards)
1
Q
The endocrine system is a:
A
System of hormone secreting glands
2
Q
The endocrine system is essential for:
A
Normal growth and development
Adaptation to internal and external environment
Contribute to the process of sexual reproduction
3
Q
The nervous system and the endocrine system interact at the:
A
hypothalamus
e.g. in the regulation of temperature, circadian rhythms and hunger etc
4
Q
Characteristics of the hormones affecting other cells’ metabolism
A
Number of molecules of hormone available
Number of receptors available
Affinity of hormone to receptor
5
Q
Name the chemical classifications of some hormones
A
Steroid e.g. testosterone, oestrogen
Peptide/ protein e.g. oxytocin, ADH, insulin
(Amine e.g. adrenaline, noradrenaline and dopamine)
NO = nitric oxide is both a neurotransmitter and hormone
6
Q
Name the sources of the hormone types
A
Steroid hormones: adrenal cortex, ovaries and testes (from embryonic mesodermal tissue)
Protein/peptide: adenohypophysis (from ectodermal tissue of the oral cavity)
Thyroid, parathyroid, pancreas (from the endodermal origin of GI tract)
Amine: thyroid, adrenal medulla (from ectodermal origin)
7
Q
What is meant by diffuse neuroendocrine system?
A
Scattered nerve cells with endocrine function
8
Q
Where is the pituitary gland located?
A
In the SELLA TURCICA of the sphenoid bone
9
Q
What is the function of the pituitary gland?
A
It produces hormones which influence the activity of the other endocrine glands
10
Q
What part of the pituitary gland is the adenohypophysis?
A
The anterior portion - the glandular part; outpouching of ectoderm of oral cavity - Ratke’s pouch
11
Q
What part of the pituitary gland is the neurohypophysis?
A
The posterior portion - the neural part - down growth from the diencephalon of the brain
12
Q
What is the blood supply to the pituitary gland?
A
Superior hypophyseal artery
Inferior hypophyseal artery
13
Q
The superior and inferior hypophyseal arteries are branches of which artery?
A
Internal carotid
14
Q
The superior hypophyseal artery supplies:
A
the median eminence &
upper part of the stalk/infundibulum
15
Q
The inferior hypophyseal artery supplies:
A
the neurohypophysis &
lower part of the stalk/ infundibulum
16
Q
The arteries that supply the median eminence and stalk/infundibulum end as what?
A
Capillary plexuses
17
Q
The capillary plexuses in the median eminence and stalk ending are drained by:
A
portal veins
18
Q
The portal veins then pass to:
A
The anterior lobe of the pituitary gland where they form a secondary plexus
19
Q
What is the significance of the portal veins which run from the capillary plexuses in the median eminence and stalk ending to the anterior lobe of pituitary?
A
It provides a route for the neurosecretory substances released from the hypothalamus to also reach the anterior lobe
20
Q
What controls hormone release from both adenohypophysis and neurohypophysis
A
Signals from the hypothalamus
21
Q
What is the shape and location of the thyroid gland?
A
A bilobed gland in the neck (4x2 cms in size) weighing ~30g
22
Q
What is the point of connection of the two lateral lobes called?
A
ISTHMUS - lies anterior to the trachea
23
Q
What the upper and lower limits of the lobes of the thyroid gland?
A
From just below the oblique line of the thyroid cartilage to the 5/6th tracheal ring, immediately anterior to the trachea
24
Q
What type of tissue is the thyroid gland derived from?
A
Endoderm
25
How does the thyroid gland develop?
It develops as a growth from the floor of the pharynx, near the base of the tongue
26
What is the role of the thyroid gland?
Essential role in regulating tissue metabolism, growth and development
27
What is secreted by the thyroid gland?
T3 - triiodothyronine
| T4 - thyroxine
28
What is the arterial supply to the thyroid gland?
Superior thyroid artery from the external carotid
| Inferior thyroid artery from the subclavian artery
29
What are the veins that drain the thyroid gland?
From an extensive plexus, the blood drains into the internal jugular and brachiocephalic veins
30
What type of surgery of the thyroid gland do you need to be careful with and why?
Cricothyrotomy - damage to the recurrent pharyngeal nerve from the vagus
31
How many parathyroid glands are there?
4 - 2 superior and 2 inferior
32
What is the location of the parathyroid glands?
Embedded in the capsule of the thyroid gland in the posterior aspect
33
How big are the parathyroid glands?
Very small - like a grain of rice and weight 40mg
34
How do the parathyroid glands develop?
Develop from endoderm tissue, mostly from cells originating from the 3rd/4th pharyngeal pouches and migrate caudally with the thymus
35
What is the role of the parathyroid glands?
To secrete parathyroid hormone
| To regulate calcium and phosphate levels in homeostasis
36
Why must the parathyroid glands be preserved during thyroidectomy?
Because if removed, the blood calcium levels all and muscles including respiratory and laryngeal go into tetanic contraction leads to death
37
What is tetanic contraction and why does it occur?
Sodium and calcium compete for entry into cells
If calcium is removed, sodium is able to enter the cell freely, the cell becomes more positive, reaches threshold and action potentials are constantly fired. This causes constant contraction of muscle and they don't relax
38
VAN of the parathyroid glands
Veins: superior, middle and inferior thyroid veins
Arteries: primarily inferior thyroid arteries (but also superior)
Nerves: from middle and inferior cervical ganglions
39
What is the location of the adrenal glands?
Superior pole of the kidneys - T12 and retroperitoneal
40
What are the shapes of the adrenal glands?
Right is pyramidal
| Left is semilunar
41
What is the function of the adrenal glands?
Hormone release in response to stress
42
What is the origin of the adrenal glands?
Cortex derived from mesoderm
| Medulla derived from neural crest cells
43
What is the function of the cortex?
To secrete corticosteroids
Cells adjacent to the capsule secrete MINERALOCORTICOIDS e.g. ALDOSTERONE - function to maintain electrolyte balance
Deeper part of cortex secretes GLUCOCORTICOIDS e.g. HYDROCORTISONE - affect metabolism and electrolyte balance
Inner part of cortex secretes ADRENAL ANDROGENS e.g. TESTOSTERONE
44
What are the secretory cells of the medulla?
Chromaffin cells
45
Where do chromaffin cells develop from?
The same embryonic tissue as the sympathetic ganglia
46
What is the medulla regarded as?
Modified sympathetic ganglion (ANS)
47
What does the medulla secrete?
Adrenaline and smaller amounts of noradrenaline (catecholamines)
48
What effect does secretion of adrenaline and noradrenaline from the medulla have?
"Fight or flight" response - affects heart rate, metabolism, blood pressure and smooth muscle of viscera
49
What is the arterial supply to the adrenal glands?
Superior suprarenal artery (from the inferior phrenic artery)
Middle suprarenal artery (from aorta)
Inferior suprarenal artery (from renal)
50
What controls the thyroid gland?
The hypothalamus releasing Thyrotrophin releasing hormone (TRH)
Pituitary gland releasing Thyroid stimulating hormone (TSH)
51
Describe the arterial supply to the cortex and medulla of the adrenal gland
The arteries branch before they enter the capsule, and the rami supply the cortex and medulla
Cortical arteries give rise to a SUBCAPSULAR PLEXUS and turn into CORTICAL SINUSOIDS that distribute blood to cortical cells
52
How many sources of blood does the medulla receive?
Two
53
What are the two sources of blood received by the medulla
1. The rami from the branched arteries (superior, middle and inferior suprarenal arteries) supplying the cortex and medulla
2. The medullary arteries which pass through the cortex to supply the medulla
54
What is the significance of the two sources of blood to the medulla?
The hormones secreted by cortical cells can influence the activity of the cells in the medulla
e.g. cortisol mediates NA conversion to adrenaline
55
What is the venous drainage of the adrenal glands?
Adrenal veins drain into the IVC (on the right)
| or renal vein (on the left hand side)
56
The activity of the adrenal glands is under the control of?
The hypothalamus & pituitary - ACTH
| Sympathetic division of the ANS - coeliac plexus and splanchnic nerves
57
How does the release of ACTH affect the adrenal glands?
ACTH stimulates secretion/release of corticosteroids
58
Describe the ANS control of the medulla
The medulla is under direct control of the ANS - sympathetic division & therefore produces a very fast response
Preganglionic sympathetic fibres end in the chromaffin cells of the medulla
The chromaffin cells release catecholamines into adjacent circulation when they receive impulses from the preganglionic sympathetic fibres
59
```
Give the definitions of the following words:
Endocrine
Autocrine
Paracrine
Neuroendocrine
```
Endocrine - the action of a hormone on a target organ far away from the secreting cell
Autocrine - the action of the hormone of the secreting cell itself
Paracrine - the action of the hormone on the adjacent cell
Neuroendocrine - neural stimulation of endocrine cells to secrete hormones e.g. medulla of the adrenal gland
60
What are the clinical manifestations of endocrine diseases?
```
Depends on whether it is:
A hormone overproduction
Hormone underproduction
OR
Tumour/mass/lesion which can be functional or non-functional
```
61
What is the difference between a functional and non-functional tumour?
A functional tumour is associated with an overproduction of hormones
A non-functional tumour is associated with a pressure effect on surrounding tissues or structures
62
What is the overall structure of an endocrine gland?
A functional unit consisting of cuboidal secretory cells with a lumen at the centre
Not all functional endocrine units have a lumen - pituitary and parathyroid gland cells have no lumen
Secretory cells supported by myoepithelial cells
63
Describe three types of cells of the anterior pituitary gland
Acidophils - take up acidic dyes - stain pink
Basophils - take up basic dyes - stain purple
Chromophobe - no specific staining features
64
Does the staining pattern relate to a specific hormone secretion?
No - ACTH is secreted by both basophils and chromophobes
65
Name the types of pathology of the pituitary gland
```
Pituitary adenoma (benign tumours)
- can be functional = secreting hormones causing HYPERPITUITARISM
or non-functional = not producing hormones - a pressure effect causing HYPOPITUITARISM
```
66
What are the space occupying effects of functional or non-functional adenomas?
```
Diplopia - double vision
Impaired vision because the skull cannot expand to allow for extra space being taken up
Headaches
Nausea
Vomiting
```
67
What effect do cancers that metastasise to the brain have?
Space occupying - build up of pressure
68
What are the names of the two hormones secreted by the thyroid gland?
Triiodothyronine T3
| Thyroxine T4
69
What is the function of T3 and T4?
To stimulate metabolic rate
70
What is required in order to synthesise T3 and T4?
Iodine
71
Where is iodine commonly found?
Sea salt
72
What condition is associated with a lack of iodine?
GOITRE - an enlarged thyroid gland
73
Why does the thyroid gland enlarge when there is a lack of iodine?
To absorb the maximum amount of iodine
74
Describe the composition of a 'normal' thyroid gland
Thyroid tissue is composed of follicles with variable sized lumina
The follicles contain colloid with an eosinophilic/pink appearance
The follicles are lined with cuboidal cells
75
The thyroid gland is highly vascular - True or False?
True
76
What is the purpose of the fenestrations in the endothelial cells lining the capillaries around the thyroid gland?
The fenestrations allow passage of the hormone into the circulation
77
What type of cells are found between the follicles?
Parafollicular cells or C cells
78
What is the function of C cells?
C cells secrete calcitonin which promotes reduction of calcium concentration in the blood
79
Describe the various types of pathology of the thyroid gland and their effects.
Goitre - enlargement of the thyroid gland - can be euthyroid
Grave's Disease - excess T3 and T4 low TSH - causing hyperthyroidism
Hashimoto's disease - low T3 and T4 high TSH - aka thyroiditis - causing hypothyroidism
Adenoma - can be euthyroid
Cancer - can be euthyroid
80
Why does multi-nodular goitre occur?
Multi-nodular just means enlargement of many nodes
Due to a lack of iodine
Goitre due to hyperplasia and hypertrophy of the thyroid cells
The gland enlarges to maximise the amount of iodine absorbed
81
How can patients with goitre be euthyroid?
Because the enlarged gland means more iodine is absorbed and so overcomes the deficiency - therefore the pt is euthyroid
82
What gives rise to the irregular appearance of the thyroid gland in goitre?
Fibrosis of the thyroid tissue but the pt is euthyroid
83
Why is it important to assess the radiology before thyroidectomy surgery?
The patient might arrest even after successful thyroidectomy due to tracheomalacia
84
What is tracheomalacia?
softening of the trachea which collapses and obstructs the airways
85
What do you do to prevent cardiac arrest during or after a thyroidectomy?
Intubate the patient
86
What causes Grave's disease?
Autoantibodies which stimulate TSH receptors
87
What is Grave's disease?
Diffuse enlargement of the thyroid gland - goitre due to hyperplasia of thyroid cells
88
What characteristic appearance does a Grave's disease thyroid gland have following thyroidectomy?
Vascular surface
89
What characteristic appearance does the colloid have in Grave's Disease and why?
The colloid has a 'soap bubble' appearance due to hyperactivity
90
Name two associated consequences of Grave's Disease
Infiltrative opthalmopathy - accumulation of soft tissue and inflammatory cells behind the eye leading to proptosis
Infiltrative dermopathy - thickening and induration of the skin on the anterior shin - pre-tibial myxoedema
91
What is Hashimoto's thyroiditis?
An autoimmune disease where the immune system destroys its own thyroid tissue
There is progressive depletion of thyroid cells by inflammation & replaced by fibrosis
92
What happens to T3, T4 and TSH in Hashimoto's thyroiditis?
Low T3/T4 and high TSH because the negative feedback is disrupted
93
Name the four main types of thyroid carcinoma
1. Papillary carcinoma (75-85%) increased risk of lymph node metastasis
2. Follicular carcinoma (10-20%) increased metastasis to bone, lung and liver
3. Medullary (5%) - arises from C cells; 20% as with MEN2 syndrome (multiple endocrine neoplasm)
4. Anaplastic (<5%) - older patients & poor prognosis
94
What is a follicular adenoma?
A benign tumour of the thyroid follicular cells - where the follicular cells join together
95
What do parathyroid glands secrete?
Parathyroid hormone (PTH)
96
What is the function of PTH?
To control levels of calcium in the blood - a decrease in blood calcium stimulates PTH secretion
97
Describe the types of pathology of the parathyroid glands
Parathyroid adenoma - involving one gland
Parathyroid hyperplasia - involving all four glands
Both cause hypercalcaemia
98
The adrenal glands consist of the adrenal cortex and medulla which are embryonically, morphologically and functionally distinct. True or false?
True
99
What colour are normal adrenal glands and why?
Orange/yellow because the cells are rich in lipids
100
Describe the different causes of adrenocortical hyperactivity
Adrenal hyperplasia, adenoma or cancer (rare)
Cushing's syndrome
Conn's syndrome
Adrenogenital syndrome
101
What is Cushing's syndrome?
Where there are excessive levels of cortisol
102
What is Conn's syndrome?
Excess levels of aldosterone
103
What's is adrenogenital syndrome?
Excess androgens
104
Describe a cause of adrenocortical insufficiency
Addison's disease
105
What are the two types of adrenal cortex adenoma?
Functional adrenal cortex adenoma - can cause Cushing's or Conn's Syndrome
Non-functional adrenal cortex adenoma
106
What is the function of the cells of the adrenal medulla?
To secrete catecholamines in response to intense emotional reaction - fight or flight hormones
107
Secretion of catecholamines (noradrenaline, adrenaline, cortisol) results in:
vasoconstriction, increased heart rate, increased blood glucose - part of organism's defence to stress
108
Why do adrenal medulla cells stain darker than cortical cells?
Because medullary cells are neuroendocrine cells
109
What is a phaeochromocytoma?
Adrenal medulla tumour
| 0.1 -0.3% cause of treatable hypertension
110
Why are phaeos called 10% tumours?
```
Because:
10% are familial as part of the MEN2 syndrome
10% are extra adrenal
10% are bilateral
10% are malignant
10% arise in childhood
```
111
What occurs as a result of a phaeo?
Due to high levels of catecholamines, there is a precipitous increase in BP, tachycardia, palpitations, headache, sweating, tremor and sense of apprehension
112
What are complications of increased BP?
Congestive cardiac failure (CCF)
Ischaemic heart disease (IHD)
Cardiac arrhythmias
Cerebrovascular accident (CVA)
