Endocrine system anat 1&2 Flashcards
- Endocrine anatomy theory component (no histology cards in here/diagrams)
Endocrine verse exocrine glands
- endocrine glands have ducts for transport of substances directly to body cavities or organs - e.g. salivary glands, sweat glands, prostate gland
- endocrine glands are ductless and secrete hormones directly into blood - e.g. pituitary gland, adrenal gland, testes
why is endocrine responses slower than neuro responses
- hormones are released from specific cells
- hormones have to diffuse to and cross capillary wall; blood transport is slower than nerves
- relies on diffusion once hormone leaves the vascular system
What are the functions of hormones?
- reproduction (Sex hormones)
- growth and development
- maintenance of internal environment (adrenals, parathyroid)
- energy production and storage (thyroid and pancreatic hormones)
Define ‘local’ hormones providing an example
- have a local effect i.e. travel short distance to effector tissue
- usually only small amounts in system (e.g. secreti)
- includes paracrine hormones which don’t even enter vasculature to reach their target organ (e.g. gastrin)
Define ‘general’ hormones including examples
- secreted by specific endocrine glands
- transported around body in blood
- cause different reactions
- some hormones have general and local effects
- some hormones have very set target tissues with specific receptors (e.g. trophic hormones - specific target to release other hormones)
What are tophic hormones
hormones that have a specific target tissue that stimulate the release of other hormones
Explain carrier molecules in relation to hormones
- hormones may circulate freely or be bound to carrier molecules
- free hormones degrade quickly while bound ones last longer*
- carrier molecules usually proteins
What is the main function of endocrine organs?
Endocrine gland contains tissue which releases hormone directly into the blood
What are the three types of endocrine organs
- Organs that are primarily endocrine (pituitary, thyroid)
- combines endocrine function with other major functions (testes, ovary)
- Relatively incidental endocrine function (diffuse endocrine system) → liver, kidneys, heat, GIT
What are the typical characteristics of the endocrine glands?
- scattered throughout body and range of embryological origins
- secrete hormones from cells
- ductless
- highly vascular (travel through blood)
- sparse connective tissue
Discuss the 4 different morphology of endocrine glands (types of endocrine glands)
- follicular → ovary, thyroid, hormones stored in follicle lumen but reabsorbed to enter capillary, NO DUCTS
- Cell masses or cord → pituitary, adrenal cortex
- Solitary endocrine cells → enteroendocrine cells
- neurocrine cells → products released into blood, hypothalamus and pineal
The 2 routes of hormones released by the hypothalamus (master gland) → explain neurosecretory cells in posterior pituitary
- Neurosecretory cells → make and transport hormones via axons (stored in ends of axons and released from here when required)
- 2 hormones released: antidiuretic hormone (ADH) and oxytocin
2 routes of hormones in the hypothalamus: explain the neurosecretory cells released into the anterior pituitary
- hormones are released into the anterior pituitary
- cause release or inhibition of the trophic hormones of the anterior pituitary
What are the 2 parts of the pituitary gland (hypophysis)
- anterior pituitary composed of: pars distalis, pars intermedia, pars tuberalis
- posterior pituitary (also composed of 3 parts)
Bone
Anatomy of the pituitary: what is it surrounded by?
Completely surrounded by sphenoid bone → thus can’t handle expansion of tissue e.g. as a result of a tumour (there is no room to expand)
*
Main hormones released from the anterior pituitary gland: note what is trophic hormone and not a trophic hormone
Thyroid stimulating hormone (trophic)
gonadotrophic hormone (FSH and LH) (trophic)
Adrenocorticotrophic hormone (trophic)
Growth hormone
prolactin
melanocyte stimulating hormone
What are the main hormones released by the posterior pituitary gland (are there any trophic hormones)
oxytocin
antidiuretic hormone
these are not trophic hormones.
Histology of the pituitary gland: What is the main cell type that produces hormones in the pituitary gland
chromophils:
- somatotrophs 45% of cells in pituitary gland (growth hormones)
- followed by mammotrophs and corticotrophs (20%)
Other cell types are chromophobes (don’t really matter much)
List the functions of the pineal gland:
- regulates diurnal and circadian rhythms (melatonin produced night-time)
- inhibits puberty (supresses gonadotrophic function until puberty)
- regulates daily fluctuations of corticosteroids (daylight/night/melatonin/cortisol release from adrenal glands)
- photoreceptor in lower vertebrate (regulates colour change)
Thyroid: What is the function of the thryoid?
- Increases metabolic rate, generating heat
What are the 2 main hormones produced by follicular cells in the thyroid gland? What else does thyroid hormone regulate (another hormone)
- Thyroxine (T4)
- Tri-iodothyronine (T3)
- Calcium regulation function: through parafollicular cells producing calcitonin (increase uptake of calcium by skeleton thus lowering blood Ca)
Why is iodine required in formation of thyroid hormones T4 and T3?
- Formed from iodinised tyrosine molecules in cuboidal follicular cells
- stores outside follicular cells in follicular lumen as inactive form thyroglobul which forms colloid
- If deficient in iodine, get build up of thyroglobulin in follicles and enlarged thyroids* (goitre in humans) → swelling of thyroid glands
Blood supply of the thyroid comes from:
- Common carotid artery
- also the cranial thyroid and caudal thyroid artery
- drains into internal jugular vein
What nerve innervates thyroid
Parasympathetic nerve supply via vagus
Sympathetic through cranial cervical ganglion
