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Endocrine glands Flashcards

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1
Q

Where is the pituitary gland located?

A

In the hypophyseal fossa of the sella turcica on the sphenoid bone.
→ It lies below the hypothalamus and is connected to it by the infundibulum.

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2
Q

How is the pituitary gland divided anatomically?

A

Into two major parts:

Anterior lobe (adenohypophysis)

Posterior lobe (neurohypophysis)
→ A small pars intermedia lies between them.

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3
Q

What are the subdivisions of the anterior pituitary (adenohypophysis)?

A
  1. Pars distalis (largest, main secretory part)
  2. Pars tuberalis (wraps around the infundibulum)
  3. Pars intermedia (rudimentary in humans)
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4
Q

What are the subdivisions of the posterior pituitary (neurohypophysis)?

A
  1. Pars nervosa (contains axons of hypothalamic neurons)
  2. Infundibular stalk (connects pituitary to hypothalamus)
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5
Q

How does the pituitary gland develop embryologically?

A

From two germ layers:

Adenohypophysis: from oral ectoderm (Rathke’s pouch)

Neurohypophysis: from neuroectoderm of the diencephalon

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6
Q

What is the blood supply to the pituitary gland?

A

Branches of the internal carotid artery:

Superior hypophyseal arteries: to median eminence and infundibulum (mainly anterior lobe)

Inferior hypophyseal arteries: to posterior lobe

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7
Q

What is the hypophyseal portal system?

A

A vascular link between the hypothalamus and anterior pituitary:
→ Capillaries in the median eminence drain into portal veins, which deliver hormones to the anterior pituitary.

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8
Q

How does venous blood drain from the pituitary gland?

A

Via hypophyseal veins into the cavernous sinus.

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9
Q

What is the histological structure of the anterior pituitary?

A

It contains chromophils (acidophils & basophils) and chromophobes.
→ Chromophils secrete various hormones.

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10
Q

What are the main cell types in the anterior pituitary and their hormones?

A

Somatotrophs → GH (growth hormone)

Lactotrophs → PRL (prolactin)

Corticotrophs → ACTH

Thyrotrophs → TSH

Gonadotrophs → FSH & LH

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11
Q

What is the function of the posterior pituitary?

A

It stores and releases hormones made in the hypothalamus:
→ ADH (vasopressin) from the supraoptic nucleus
→ Oxytocin from the paraventricular nucleus

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12
Q

What is the role of pituicytes in the neurohypophysis?

A

Pituicytes are specialized glial cells that support the axons in the pars nervosa.

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13
Q

What is the functional role of the pituitary gland?

A

It is the master endocrine gland, regulating growth, metabolism, reproduction, and stress through hormone release.

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14
Q

What is the embryological origin of the anterior pituitary (adenohypophysis)?

A

It originates from an upward-growing finger of ectoderm from the roof of the mouth, called Rathke’s pouch.

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15
Q

What is the embryological origin of the posterior pituitary (neurohypophysis)?

A

It develops from a ventral evagination of neuroectoderm from the diencephalon.

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16
Q

What is the weight and location of the pituitary gland?

A

It weighs 600–900 mg and sits in the hypophyseal fossa of the sella turcica of the sphenoid bone.

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17
Q

What are the anatomical relations of the pituitary gland?

A

Anterior: sphenoid sinus

Posterior: posterior intercavernous sinus, basilar artery, pons

Superior: diaphragm sellae, optic chiasm

Inferior: sphenoid sinus

Lateral: cavernous sinus

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18
Q

What does the pars tuberalis of the adenohypophysis do?

A

It covers the anterior part of the infundibulum and tuber cinereum.

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19
Q

What are the three parts of the neurohypophysis?

A

Pars nervosa – main bulk

Median eminence – upper part

Infundibular stalk – connects pars nervosa to the base of the brain

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20
Q

Which arteries supply the posterior lobe of the pituitary?

A

Superior hypophyseal artery

Infundibular artery

Inferior hypophyseal artery

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21
Q

Which veins drain the anterior and posterior lobes of the pituitary?

A

Anterior hypophyseal veins: drain the anterior lobe

Posterior hypophyseal veins: drain the posterior lobe

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22
Q

What proportion of anterior pituitary cells are chromophobic?

A

About 50%, representing non-secretory cells or precursors of the other types.

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23
Q

What are the types of acidophils in the anterior pituitary, and what do they secrete?

A

Somatotrophs → GH

Lactotrophs → Prolactin

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24
Q

What are the types of basophils in the anterior pituitary, and what do they secrete?

A

Thyrotrophs → TSH

Gonadotrophs → FSH

Luteotrophs → LH & ICSH

Corticotrophs → ACTH (Note: You had this under acidophils in the text, but it’s a basophil in standard sources.)

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25
What are pituicytes and where are they found?
Pituicytes are glial cells found in the posterior lobe (pars nervosa) of the pituitary gland.
26
What are the hypothalamic nuclei that give rise to the hypothalamo-hypophyseal tract?
Supraoptic nucleus → ADH Paraventricular nucleus → Oxytocin
27
Where is the pineal gland located?
In the epithalamus, near the posterior wall of the third ventricle, between the superior colliculi and above the cerebellar vermis. → Attached by a stalk to the roof of the third ventricle.
28
How does the pineal gland develop?
From the neuroectoderm of the diencephalon during embryogenesis.
29
What is the macroscopic structure of the pineal gland?
A small, conical neuroendocrine organ ~5–8 mm in length. → Enclosed by pia mater, which sends septa inward, dividing it into lobules.
30
What are the two main cell types in the pineal gland?
Pinealocytes – the main endocrine cells Interstitial (glial) cells – supportive astrocyte-like cells
31
What is the role of pinealocytes?
They synthesize and secrete melatonin, especially during darkness. → Melatonin regulates circadian rhythms, sleep–wake cycles, and seasonal reproductive cycles.
32
How is pineal activity controlled?
By sympathetic innervation from the superior cervical ganglion, via pathways from the retina through the hypothalamus. → Darkness stimulates melatonin production; light inhibits it.
33
What are "brain sand" or corpora arenacea?
Calcified deposits (mainly calcium and magnesium salts) found in the pineal gland with age. → They are radiologically visible and increase with age.
34
What is the vascular supply of the pineal gland?
Mainly from the posterior choroidal arteries, branches of the posterior cerebral artery. → Venous drainage is into the internal cerebral veins.
35
What is the histophysiological function of the pineal gland?
Secretion of melatonin, which: Inhibits gonadotropin-releasing hormone (GnRH) Modulates circadian rhythm Has antioxidant properties Regulates immune responses and puberty onset
36
Does the pineal gland have a blood-brain barrier?
No — it is one of the circumventricular organs, allowing it to sense blood-borne signals and release hormones directly into circulation.
37
What is the size and weight of the pineal gland?
It is about 10 mm long and weighs approximately 160 mg.
38
What is the shape and precise anatomical location of the pineal gland?
It is pine-cone shaped and lies between the habenular commissure and the posterior commissure, on the posterior wall of the third ventricle.
39
What is the embryological origin of the pineal gland?
It is derived from the neuroepithelium of the diencephalon, specifically in the roof of the third ventricle, and remains connected to the brain via the habenulae.
40
What is the evolutionary (phylogenetic) origin of the pineal gland?
It originally functioned as a photosensory organ and later evolved into a neuroendocrine gland.
41
What hormones are secreted by the pineal gland besides melatonin?
In addition to melatonin, it secretes indoles and peptides, especially alpha-melanocyte-stimulating hormone (α-MSH).
42
What is the histological structure of the pineal gland’s parenchyma?
It contains pinealocytes arranged in lobules, divided by connective tissue septa, and supported by a stroma of astrocyte processes.
43
What types of glial cells are found in the pineal gland?
Fibrous astrocytes, which act as supporting glial cells.
44
What is the innervation of the pineal gland?
It is innervated by sympathetic nerves whose cell bodies are in the superior cervical ganglion.
45
From which embryological structure does the thyroid gland develop?
From the epithelium of the floor of the mouth → It descends to its final position between C5–T1
46
What is the topographical position of the thyroid gland?
Lies anterolateral to the trachea and larynx, between vertebral levels C5–T1 → It has two lateral lobes connected by an isthmus and is enclosed in pretracheal fascia
47
What are the dimensions and weight of the thyroid gland?
Weight: 18–60 g; Lobes: 4–8 cm long, 2–4 cm wide, 1.5–2.5 cm thick → Isthmus: 1.5–2.0 cm wide, 0.5–1.5 cm thick
48
What is the pyramidal lobe of the thyroid gland?
A superior projection from the cranial border of the isthmus → Represents a developmental remnant of the thyroglossal duct
49
What are the two layers of the thyroid fibrous capsule?
Internal capsule (thin, vascularised) and external capsule (part of pretracheal fascia) → The space between them is filled with loose connective tissue
50
Which arteries supply the thyroid gland?
Superior thyroid artery (supplies superior, anterior, lateral parts); Inferior thyroid artery (supplies inferior, posterior, medial parts)
51
Which veins drain the thyroid gland?
Superior thyroid vein (into internal jugular vein); Inferior thyroid vein (into brachiocephalic vein)
52
What is the innervation of the thyroid gland?
Sympathetic: from superior cervical and cervicothoracic ganglia; Parasympathetic: from superior and recurrent laryngeal nerves
53
What is the microscopic structure of the thyroid gland?
It has approx. 3 million closed follicles → Follicles are spherical or tubular, lined with epithelial cells (flattened to columnar), surrounded by fine connective tissue and fenestrated capillaries
54
What are parafollicular (C) cells and what do they produce?
Found in interfollicular tissue, derived from neural crest → Secrete calcitonin (lowers blood calcium)
55
What are the main hormones produced by the thyroid gland and their effects?
T3 (triiodothyronine), T4 (thyroxine): stimulate metabolism, essential for development; Calcitonin: regulates calcium levels
56
Describe the steps in the synthesis and release of thyroid hormones (T3 and T4).
Thyroglobulin binds iodide (oxidised to iodine); iodinated thyroglobulin is endocytosed; TSH stimulates lysosomal digestion, releasing T3/T4 into blood by diffusion
57
How many parathyroid glands are there, and what is their color?
There are four parathyroid glands: 2 superior and 2 inferior, typically yellow to reddish-brown in color.
58
What is the total weight of the parathyroid glands?
About 120–160 mg in total.
59
Where are the parathyroid glands located?
At the level of the caudal margin of the cricoid cartilage, embedded in the posterior surface of the thyroid gland.
60
What is the origin of the superior and inferior parathyroid glands?
Superior parathyroid glands: from the 4th pharyngeal pouch Inferior parathyroid glands: from the 3rd pharyngeal pouch
61
Where is the inferior parathyroid gland typically located?
Near the base of the lateral lobes of the thyroid, at the level of the 3rd and 4th tracheal cartilages.
62
What surrounds the parathyroid glands?
A connective tissue capsule.
63
What is the histological composition of the parathyroid gland?
Contains granular epithelium with connective tissue fibers, adipose cells, and fenestrated capillaries. Organized into cords or clusters.
64
What are the two main cell types in the parathyroid gland?
Chief cells → Secrete parathyroid hormone (PTH) Oxyphil cells → Function unknown
65
What are the actions of parathyroid hormone (PTH)?
Increases osteoclast activity, mobilizing calcium from bone Increases blood calcium levels Promotes phosphate excretion by the kidneys
66
What is the arterial supply to the parathyroid glands?
Superior thyroid arteries Inferior thyroid arteries (→ parathyroid artery) Thyroid ima artery Laryngeal, tracheal, and oesophageal arteries (collateral supply)
67
How is venous blood drained from the parathyroid glands?
Through the thyroid plexus of veins.
68
What are the suprarenal glands and where are they located?
Paired retroperitoneal endocrine glands located over the medial aspects of the upper poles of each kidney.
69
What is the shape of the right and left adrenal glands?
Right: Triangular, with a distinct apex; lies behind the liver and IVC Left: Crescent-shaped; no distinct apex; in contact with the omental bursa and posterior stomach wall
70
What is the weight of a suprarenal gland?
Each gland weighs approximately 4.2–5.0 grams.
71
What covers the adrenal glands?
A common connective tissue capsule surrounds each gland.
72
What enters and exits through the adrenal hilum?
Arteries and nerves enter, Veins and lymphatics exit
73
What is the embryological origin of the adrenal cortex and medulla?
Cortex: from mesoderm Medulla: from neuroectodermal sympathoblasts
74
What are the three zones of the adrenal cortex and their functions?
Zona glomerulosa → Secretes mineralocorticoids (e.g., aldosterone) Zona fasciculata → Secretes glucocorticoids (e.g., cortisol) Zona reticularis → Secretes androgens (e.g., DHEA), small amounts of corticosteroids
75
What is characteristic of the histology of the adrenal cortex?
Glandular epithelium surrounded by basal laminae and reticular fibers Rich in lipids, appears yellow Zona fasciculata is rich in cholesterol esters, vitamins A and C
76
What does the adrenal medulla secrete and what are its functions?
Catecholamines (epinephrine and norepinephrine) → for fight or flight response Enkephalins → act in pain modulation
77
Which arteries supply the adrenal glands?
Superior adrenal artery (from inferior phrenic artery) Middle adrenal artery (from aorta) Inferior adrenal artery (from renal artery)
78
Where do the adrenal veins drain?
Right adrenal vein → directly into the inferior vena cava Left adrenal vein → into the left renal vein
79
What are paraganglia?
Small, nodular, pea-sized neuroendocrine structures containing chromaffin cells that secrete catecholamines.
80
What is the embryological origin of paraganglia?
Arise from neural crest cells.
81
What is the largest group of paraganglia in the body?
The aortic paraganglia, which are irregularly distributed in the retroperitoneal space.
82
What is the structural organization of the endocrine pancreas?
Islets consist of columns of epithelial cells supported by a capillary network.
82
Where are the endocrine pancreatic cells located?
In the islets of Langerhans, which lie within or near the margins of the lobules of the exocrine pancreas.
83
How many islets of Langerhans are in the pancreas, and what are their size and total weight?
Approximately 0.5–1.5 million islets, each 100–200 µm in diameter, with total endocrine tissue weight about 2–5 g.
84
What percentage of the islet cells are alpha cells and what do they secrete?
15–20%; they lie at the periphery of the islets and secrete glucagon. → Glucagon raises blood glucose by promoting glycogenolysis and gluconeogenesis.
84
What is the most abundant cell type in the islets of Langerhans?
Beta cells – about 70% of the islet; they secrete insulin, which stimulates glycogen synthesis and lowers blood glucose.
85
What do delta cells secrete and what is their function?
Delta cells (5%) secrete somatostatin, which inhibits insulin and glucagon secretion.
85
What do PP cells produce and what is their function?
Pancreatic polypeptide, which acts as an antagonist to cholecystokinin (CCK) and inhibits exocrine pancreatic secretion.
86
What do D1 cells produce and what is the effect?
Vasoactive intestinal polypeptide (VIP), which causes vasodilation.
87
How is the endocrine pancreas vascularized?
Supplied by arterioles from the islet capillary network and drained via the pancreatic vein into the hepatic portal vein.
88
What is the gastro-entero-pancreatic (GEP) endocrine system?
A diffuse neuroendocrine system comprising hormone-secreting cells found throughout the GI tract and pancreas.
89
What is the general function of the GEP endocrine system?
It regulates digestion, motility, absorption, and secretion via hormones like gastrin, secretin, CCK, motilin, VIP, and GIP.

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