Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Endocrine > Thyroid Physiology and Anatomy > Flashcards

Thyroid Physiology and Anatomy Flashcards

1
Q

Thyroid Gland

A

Largest endocrine gland
Only endocrine gland which is superficial and allows palpation

Requires substances from the environment to synthesise hormone

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Thyroid gland embryology

A

4th week of human embryogenesis

  • Midline thickening at back of the tongue and stretches downwards
  • Migrates in front of larynx and comes into close proximity with parathyroid glands
  • Comes into contact with cells from lower part of the pharynx (become C-cells - produce calcitonin)

End of 2nd month

  • 2 lobes joint at isthmus in front of trachea
  • Thyroglossal duct loses contact (does not occur in 15% of population0

Week 12
- Primitive follicles become visible as simple epithelium surrounding central lumen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Thyroid Gland point of origin remnant

A

Point of origin in tongue persists as foramen caecum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Failure of development

A

Congenital hypothyroidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Under or over migration

A

Lingual or retrosternal thyroid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Failure of thyroglossal duct to recess

A

thyroglossal cyst

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Thyroid gland vertebral levels

A

C5, C6, C7 and T1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Secretions of. thyroid gland tissues

A

Thyroxine (T4)
Tri- iodothyronine (T3)
Calcitonin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

parathyroid gland secretions

A

4 parathyroid glands

Secrete parathyroid hormone (PTH)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Thyroid gland shape

A

‘butterfly shape’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Thyroid gland innervation

A

Autonomic nerve supply

Parasympathetic
- vagus nerves

Sympathetic
- superior, middle and inferior ganglia of sympathetic trunk

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Thyroid gland blood supply

A

Superior and inferior thyroid arteries

- branch of external carotid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Thyroid gland venous drainage

A

Superior/ middle thyroid vein
- drains to internal jugular

inferior thyroid vein
- drains to brachiocephalic vein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Thyroid gland support

A

Supported by ligaments and strap muscles

Posteromedial aspect of the gland is attached by posterior suspensory ligament (Berry ligament)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

basic function unit of thyroid gland

A

Follicle

  • colloid surrounded by follicular cells
  • parafollicular cells

Richly vascularised and innervated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Control of thyroid gland

A

Controlled by negative feedback loop

Thyroid is controlled by TSH from the pituitary gland. (in turn regulated by TRH from hypothalamus)

T3 predominantly completes the. negative feedback loop by suppressing the production of TSH and TRH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Underactive thyroid

A

High TSH as compensatory

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Thyroid Hormone Synthesis (6)

A
  1. Thyroglobulin synthesis (thyroxine rich protein- exclusively made by follicular cells)
  2. Uptake and concentration of iodide
  3. Oxidation of iodide to iodine.
  4. Iodination of thyroglobulin
  5. Formation of MIT and DIT
  6. Secretion
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Synthesis and storage of T3 and T4 (4)

A
  1. Iodine taken up by follicle cells
  2. Iodine attached to tyrosine residues on thyroglobulin to form MIT and DIT
  3. Coupling of
    MIT + DIT =T3
    DIT + DIT = T4
  4. Stored in colloid thyroglobulin till required
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Effect on carbimazole and Propylthiouracil on synthesis and storage of T3 and T4

A

Step 3 can be inhibited:
Iodine unable to attach to tyrosine residues on thyroglobulin - No formation of MIT and DIT

Used to treat hyperthyroidism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Thyroid Hormone- T4

A

Thyroxine
90% of thyroid hormones secreted
Converted to T3 by liver and kidney
Not biologically active

22
Q

Thyroid Hormone - T3

A

Tri-iodothyronine
10% of thyroid hormones secreted
Major biologically active thyroid hormone

23
Q

Thyroid hormone transport

A

Bound to serum proteins

  • thyroxine binding globulin (TBG)
  • Thyroxine binding pre-albumin (TBPA)
  • Albumin

Only unbound hormones can enter cells

24
Q

Thyroid binding globulin (TBG)

A

T4 and T3 are almost entirely bound by plasma proteins

T3 has a more rapid onset and offset of actions as its less avidly bound

Only free/unbound hormone is available to tissues

Metabolic state correlates more freely with the total concentration in the plasma

Concentration of total hormone does not necessarily vary directly with that of free hormones .

25
Q

Increased TBG

aetiology

A

Increases total T4 (but not free T4)

Pregnancy
Newborn state
OCP and other sources. of oestrogen 
Hepatitis A
Chronic active hepatitis 
Biliary cirrhosis 
Acute intermittent porphyria 
Genetics
Clofibrate
Heroin
26
Q

Decreased TBG

aetiology

A

Decreases total T4 (but not free T4)

Androgens 
Karge doses of glucocorticoids 
Cushing Syndrome 
Active acromegaly 
Severe systemic illness
Chronic liver disease
nephrotic syndrome 
Genetics 
Pheytoin 
Carbamzepine
27
Q

Effects of Thyroid Hormone (all cells, especially neurons)

A

Increased metabolic rate

Increased glucose uptake

28
Q

Effect of thyroid hormone on liver tissue

A

Increased glycogenolysis and gluconeogenesis

Decreased glycogenesis

29
Q

Effect of thyroid hormone on adipose connective tissue.

A

Increased lipolysis

Decreased lipogenesis

30
Q

Effect of thyroid hormone on lungs

A

Increased breathing rate

- Helps meet increased O2 demand for aerobic cellular respiration

31
Q

Effect of thyroid hormone on heart

A

Increased heart rate
Increased force of contraction

Helps meet increased O2 demand for aerobic cellular respiration

32
Q

thyroid hormone physiological effect

A

target virtually every tissue
Occurs throughout life to alter. gene transcription and protein synthesis

Profound effects on

  • metabolism
  • growth
  • developement
  • reproduction
  • behaviours
33
Q

Thyroid Hormone Effect: Metabolic rate

A

Increases metabolic rate

increase number and size of mitochondria
Increases oxygen use and rates of ATP hydrolysis
Increase synthesis of respiratory chain enzymes

34
Q

Thyroid Hormone: Thermogenesis

A

Increases thermogenesis

~ 30 % of temperature regulation due to thyroid hormone thermogenesis

35
Q

Thyroid Hormone: Carbohydrate metabolism

A

Increases blood glucose
- stimulation of glycogenolysis and gluconeogenesis

Increased insulin dependent glucose uptake into cells

36
Q

Thyroid Hormone: Lipid metabolism

A

Mobilise fats from adipose tissue

Increases fatty acid oxidation in tissues

37
Q

Thyroid Hormone; Protein Metabolism

A

Increases protein synthesis

38
Q

Thyroid Hormone: Growth and Development

A

Growth Hormone releasing hormone (GHRH) production and secretion requires thyroid hormones

Glucocorticoid-induced GHRH release also dependent on thyroid hormones

GH / Somatomedins require presence of thyroid hormone for activity

39
Q

Thyroid hormone: development of foetal and neonatal brain

A

Myelinogenesisi and axonal growth require thyroid hormone

40
Q

Thyroid Hormone: CNS activity

A

Hypothyroidism: Slow intellectual functions

Hyperthyroidism: nervousness, hyperkinesis and emotional liability

41
Q

Thyroid Hormones Permissive Sympathomimetic Action

A

Thyroid hormones increase responsiveness to adrenaline and sympathetic NS neurotransmitter, noradrenaline, by increasing number of receptors

CV responsiveness also increased due to this affect
- increase force and rate of contraction

42
Q

use of beta-blocker in hyperthyroidism

A

Need to use beta-blocker (egg, propranolol) to treat symptoms in initial stages if therapy for hyperthyroidism,

43
Q

De-iodinase Type 1

A

D1

Found in liver and kidney

44
Q

De-iodinase type 2

A

D2

Found in heart, skeletal muscle, CNS, fat, thyroid and pituitary

45
Q

De-iodinase type 3

A

D3

Found in foetal tissue, placenta and brain (except pituitary)

46
Q

Degradation of thyroid hormones

A

Thyroid produces T4 and T3 which enter circulation and peripheral tissues

T4

  • 15% go to minor degradative pathways
  • 45% converted by D3 into inactive reverse T3 and then rapidly excreted
  • 40% converted by D1 into T3

T3

  • can become biologically active
  • converted to Inactive T2 by D3

In the brain and pituitary thyrotroph
- T4 converted to T3 by D2. T3 then contributes to negative feedback on TRH and TSH

47
Q

Hypothyroidism

A

Deficiency of thyroid hormones

48
Q

Hypothyroidism aetiology

A

Primary (gland) failure
- may be associated with goitre

Secondary to TRH or TSH
- no goitre

lack of iodine in diet

49
Q

Hypothyroidism symptoms

A 
Reduced BMR
Slow pulse rate
Fatigue, lethargy. slow response times and mental sluggishness
Cold-intolerance
Tendency to put on weight easily

In adults
-myxoedema

babies
- Cretinism (dwarfism and limited mental functioning)

50
Q

Hyperthyroidism Aetiology

A

Graves Disease
Toxic adenoma
Toxic nodule in MNG

51
Q

Graves disease

A

Autoimmune
- TSH receptor antibodies act like TSH but are unchecked by T3 and T4

Exopthalmos (bulging eyes)
Goitre

52
Q

Hyperthyroidism symptoms

A 
Increased BMR
Very fast pulse rate 
Increased nervousness and excessively emotional 
Insomnia 
Sweating and heat intolerance
Tendency to lose weight easily

Endocrine (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions