Endocrine system Flashcards
Which organs are included in the endocrine system (6)?
Gonads
Pancreas
Pituritary gland
Thyroid gland
Parathyroid glands
Adrenal glands
Are peptide hormones soluble in water?
Yes
Do peptide hormones need a transporter?
No because they are soluble in water and can travel through the membrane
They need a receptor
What do endocrine organ secrete?
Signals in form of hormones
Do steroid hormones need a receptor?
Yes
Are steroid hormones soluble in water?
No
What does the hypothalamus-hypophyseal system target?
Other endocrine glands
What does the hormones from the hypothalamus stimulate?
The pituitary gland
2 parts of the pituitary gland
Adenohypohysis
Neurophypohysis
Different name for pituitary gland
Hypophisis
What is the part of the CNS that includes the hypothalamus called?
Diencephalon
Which 7 structures forms the border of the hypothalamus?
Superior: Hypothalamic sulcus
Inferior: Optic chiasm, tuber cinereum, mammillary body and infundibulum
Anterior: Lamina terminalis
Posterior: Midbrain
What is the small swelling in the tuber cinereum called (located behind the infundibulum)?
Median eminence
What is the connection between the pituitary gland and thalamus called?
Infundibulum
Functions of the hypothalamus
Regulation of food and water intake
Sleep-wake cycle
Sexual behaviour patterns
Defence mechanisms against attack
What kind of tissue is the neurohypophysis?
Nervous tissue
What cells are the adenohypophysis made of?
Endocrine cells
Origin of neurohypophysis
Diencephalic downgrowth
Origin of adenohypophysis
Ectodermal derivative
Which is anterior, neurohypophysis or adenohypophysis?
Adenohypophysis
What forms the infundibular stem?
Axons of neurons which body is located in the hypothalamus
What forms the neural stalk (connection of hypothalamus and pituitary gland)?
Median eminence
Infundibular stem
3 regions of the hypothalamus
Anterior (supraoptic)
Middle (tuberal)
Posterior (mammillary)
Where is the body of the parvocellular neurosecretory cells located?
Inside the middle part of the hypothalamus
Where is the axons of the parvocellular neurosecretory cells located?
Infundibular
Is there a portal system in the pituitary gland?
Yes
What are the 2 magnocellular nuclei called?
Paraventricular nucleus
Supraoptic nucleus
What supplies the primary capillary plexus in the upper infundibulum?
Superior hypophysial artery
How many capillary beds in the hypothalamohypophysial portal system?
2
Which hormones do the basophils contain?
Glycoprotein hormones
Which hormones do the acidophils contain?
Polypeptide hormones
What do lactotrope cells produce?
Prolactin
What do somatotrope cells produce?
Growth hormone
What do thyrotropes cells produce?
Thyroid stimulating hormones
What do gonadotropes cells produce?
Luteinising hormone or follicle stimulating hormone
What do corticotropes cells produce?
Adrenocorticotrophic hormone
Where is the thyroid gland located?
Lower neck, C5-T1
When does the thyroid gland enlarge in women?
During menstruation and pregnancy
What connects the 2 lobes of the thyroid?
The isthmus
What muscles protect the thyroid gland?
The infra hyoid muscles
-> Omohyoid, sternohyoid muscle, sternothyroid and thyrohyoid muscle
Where are the parathyroid gland attached?
Thyroid
What is the thin capsule of the thyroid gland made of?
Connective tissue
What is the functional unit of the thyroid gland?
Follicles
What shape does the follicles have?
Spherical and cyst like
What is the core of the follicles made up of?
Central colloid core
What is the colloid?
Storage form of thyroid hormone
What is iodothyroglobulin?
The inactive stored form of the active thyroid hormones
What produced T3 and T4?
The follicular epithelial cells
Which follicles are large? resting or active?
Resting
Why are resting follicles large and lined by squamous or low cuboidal epithelium?
Because they store a lot of hormones
Why are active follicles small and lined by cuboidal cells?
Because they are secreting hormone via endocytosis
What 2 types of cells in the thyroid gland?
Follicular cells
C cells
Where are C cells found in the thyroid gland?
Inbetween follicular cells
What does C stand for in C cells?
Clear
Calcitonin
Calcium
What do C cells produce?
Calcitonin (thyrocalcitonin)
Where are the arteries that supply the thyroid gland from?
External carotid artery
Thyreocervical trunk (branch of subclavian artery)
3 veins of the thyroid gland
Superior thyroid vein
Inferior thyroid vein
Superficial branch
What is the color of the parathyroid glands?
Yellow-brownish
Embrylogical origin of the parathyroid glands?
Endodermic origin
What does it mean that parathyroid glands are ectopic?
That they are in an unusual place
2 cell types in the parathyroid
Chief cells
Oxyphil (eosinophil) cells
Where are the suprarenal (adrenal) glands located?
Above the adipose of each kidney
What is the position of the adrenal glands?
Retriperotoneal
Which adrenal gland is longer?
The left
Does the renal fascia also contain the adrenal glands?
Yes
What are the renal fascia surrounded by?
Renal fascia and peri renal adipose tissue (fat)
Shape of the left adrenal gland
Semilunar
Shape of the right adrenal gland
Pyramidal
3 superrenal arteries for each adrenal gland
Superior, middle and inferior suprarenal arteries
Where does the superior suprarenal arteries branch from?
Inferior phrenic arteries
Where does the middle suprarenal arteries branch from?
Directly from the aorta
Where does the inferior suprarenal arteries branch from?
Renal arteries
What does the vein from the right adrenal gland drain into?
Directly into the inferior vena cava
What does the vein from the left adrenal gland drain into?
Left renal vein
Does the renal glands have their own capsule?
Yes
What does the cortex of the adrenal glands synthesise?
Steroid hormones
What does the medulla of the adrenal glands synthesise?
Catecholamines (adrenalin and noradrenalin)
3 different part of the cortex of the adrenal gland
Zona glomerulosa
Zona fasciculata
Zona reticularis
What is the endocrine system?
Communication between different parts of the body
What is the endocrine system vital for maintaining?
Homeostasis
What does angiotensin and renin regulate?
Blood pressure and renal filtration
What are hormones transported via?
The bloodstream
Why are endocrine glands vascularised with a dense microvascular network?
Because hormone transport take place via the bloodstream
What does the microenvironment of the microvasculature of endocrine glands harbour?
Stem and progenitor cells
Via what does the hypothalamus control the production and secretion of numerous hormones in the pituitary gland?
Neuroendocrine signals
What do the hormones released into the bloodstream from the hypothalamus trigger?
The release of hormones from their target glands which in turn affect organ function
What regulates the hormone level?
Feedback mechanisms
What creates a negative feedback loop?
When hormones from target glands reach a certain concentration in the blood
What does the negative feedback loop do?
Inhibits further hormone release in the hypothalamus and pituitary gland
Where is the pituitary gland contained?
In the hypophyseal fossa
Different name for adenohypohysis of the pituitary gland
Anterior lobe
Different name for Neurohypophisis of the pituitary gland
Posterior lobe
Neural lobe
What kind of structure is the hypothalamus?
Bilateral, paired structure
In what 2 areas does the hypothalamus have major functions?
Homeostasis and survival
What does the homeostatic functions by the hypothalamus include?
Control of body temperature and circulation of blood
What is the pituitary gland continuos with?
Infundibulum
In which bone is the pituitary fossa found?
Sphenoid bone
What is the pituitary gland covered by superiorly?
A circular diaphragma sellae of dura mater
What does the dura mater that covers the pituitary gland superiorly form?
A bridge pierced by the sellae dorsal
When during development does the pituitary gland loose contact with the primitive oral cavity?
When rathe’s pouch is pinched off
What does the central infundibular stem contain?
Neural hypophyseal connections
What is the central infundibular stem continuous with?
The median eminence of the tuber cinereum
What is the infundibular stem formed by?
Axons of neurons whos body is in the hypothalamus
What part of the adenohypophysis surrounds the infundibular stem?
The pars tuberalis
What part of the adenohypophysis is the largest?
Pars distalis
What is in-between neurohypophysis and adenohypophyis?
The pars intermedia
3 parts of the adenohypophyis
Pars tuberalis
Pars intermedia
Pars distalis
How are the endocrine cells of the adenophysis classified?
According to their staining
What does the staining of the endocrine cells of the adenophysis reflect?
Their hormone production which reflects their function
Which part of the hypothalamus is above the infundibulum?
The middle (tuberal)
What does the parvocellular neurons reach?
The infundibular capillary bed
What does the action potentials of pravocellular neurons result in?
Calcium-dependent exocytosis of releasing hormones or inhibiting hormones into the capillary bed
What are the pravocellular neurons transport to?
Adenohypophysis
What does magnocellular neurons give rise to?
The hypothalamohypophyseal tract
What does the hypothalamohypophyseal tract descend to?
The neurohypophysis
2 hormones secreted directly to the capillary bed by magnocellular nuclei
Antidiuretic hormone (vasopressin)
Oxytocin
What makes up nearly half the volume of the neurophypophysis?
Axon swellings containing the secretory granules for antidiuretic hormone and oxytocin
Which nuclei does the neurons which secrete antidiuretic hormone and oxytocin belong to?
Supraoptic
Paraventricular nuclei
Which artery does the superior hypophyseal artery anastomoses with?
Inferior hypophyseal artery
Which vein connects to the inferior hypophyseal artery capillary bed?
Hypophysial vein
Which lobe of the pituitary gland is the secondary capillary plexus located in?
Anterior lobe
What tissue is the adenophypophysis composed of?
Winding cords of epithelial cells flanked by vascular sinusoids
3 types of cells seen in adenophypophysis when staining
Acidophils
Basophils
Chromophobes
How does acidophils stain?
Their cytoplasm stains red or orange
How does basophils stain?
Their cytoplasm stains blueish
How does chromophobes stain?
They cytoplasm stains very poorly
What kind of hormones does the acidophil cells contain?
Polypeptide hormones
What kind of hormones does basophil cells contain?
Glycoprotein hormones
How much hormone content is found in chromophobes?
Little to none
What kind of cells can chromphobes in adenohypophysis be?
Acidophils or basophils that have granulated and are depleted of hormones
Stem cell that haven’t differentiated into hormone producing cells
What is the posteromedial aspects of the lobes of the thyroid gland attached to?
The side of the cricoid cartilage
What connects the lower part of the lobes of the thyroid gland?
The isthmus
Where is the isthmus typically?
Anterior to the 2nd and 3rd tracheal cartilage.
However the site greatly varies
Is the conical pyramidal lobe always present?
No, often absent or small
Where does the conical pyramidal lob ascend towards?
The hyoid bone
What is the convex lateral surface of the thyroid gland covered by?
Sternothyroid
What prevents the upper pole of the gland from extending o to thyrohyoid?
Attachments of the sternothyroid muscle
From lateral to medial how is the neurovascular bundle of the neck organised
Jugular vein
Vagus nerve
Common carotid artery
Name of fascia in the neck
Pretracheal (visceral)
What is the thyroid gland developed from?
Endocermal cells
Where in the embryo is the thyrogloassal duct?
Posterior to the tongue
What is the central collie core of follicles surrounded dby?
A single-layered epithelium
What does the central colloid core rest on?
Basal lamina
What does colloid consist of?
Iodinated glycoprotein
Iodothyroglobulin
What is iodothyroglobulin?
The inactive stored form of the active thyroid hormones
What is iodothyroglobulin produced by?
The follicular epithelial cells
What does the follicular cell type depend on?
Their level of activity
What controls the follicular cells’ level of activity?
Hypophysial thyroid-stimulating hormone (TSH, thyrotropin)
Wha does the peptide hormone calcitonin do?
Lowers blood calcium
What is the venous drainage of the thyroid gland usually via?
Superior, middle and inferior thyroid vein
Where do the parathyroid glands usually lie?
Between the posterior lobar borders of the thyroid gland and its capsule
How many parathyroid glands are there typically?
2 on each side
What are the parathyroid glands usually supplied by?
The inferior thyroid arteries
What is the endodermic origin of the parathyroid glands?
3rd and 4th pharyngeal pouch
What is the capsule of the parathyroids made up of?
Connective tissue
Does the parathyroid glands have distinct lobules?
No
What do the parathyroid glands synthesize and secrete?
Parathyroid hormone (PTH)
What makes the number of oxyphil cells in the parathyroid increase?
Age
When are chief cells dominant in the parathyroid glands?
In childhood
When does adipose tissue accumulate in the stroma?
After puberty
Where does the right adrenal gland lie in relations to the inferior vena cava?
Posterior
What separates the right adrenal gland and the inferior vena cava?
A thin layer of fascia and connective tissue
What does the left adrenal gland lie closely to?
Left crus of the diaphragm
What separates the left adrenal gland and the crus of the diaphragm?
A thin layer of fascia and connective tissue
Where does the medullary veins emerge from?
The hilum
Wheat does the medullary veins form?
A suprarenal vein
What does the right suprarenal vein pass into?
Directly into the inferior vena cava
What does the left suprarenal vein pass into?
Left renal vein
What is the adrenal glands capsule like?
Thick collagenous
What forms the main mass of the adrenal glands?
An outer cortex
Do the zones of the suprarenal cortex synthesize the same hormones?
No they each synthesise a specific hormone
Is the function of androgen the same in both genders?
Yes
What makes up 70% of the cortex of the adrenal glands?
The zona fasciculata
What is the suprarenal medulla composed of?
Groups and columns of chromatin cells separated by wide venous sinusoids and supported by a network of reticular fibers
What are chromaffin cells functionally equivalent to?
Postganglionic sympathetic neurons
What are chromaffin cells dericatives of?
Neural crest
What do chromaffin cells do?
Synthesise, store and release noradrenaline and adrenaline
What is 80% of what is produced by the chromaffin cells in the suprarenal medulla?
Adrenaline
What mediates the release of adrenaline and noradrenaline into the venous sinusoids?
Sympathetic neurones
How is adrenaline stored?
In small granules
How is noradrenaline stored?
In large granules
Do some cells of the suprarenal medulla synthesize both noradrenaline and adrenalin?
Yes
What does a double plexus of the adrenal glands show?
That it may have function in productions of the other hormones
