endocrine system Flashcards
What is the pineal gland?
biological clock
endocrine gland
has no nervous output
size of pineal gland
7x6x3 mm
where is the pineal gland?
in groove between thalamic bodies
relations of the pineal gland
anterior: third ventricle (pineal recess),
posteroinferior: superior cerebellar cistern,
superior: internal cerebral veins, vein of Galen (posteriorly), stria medularis, splenium of the corpus callosum and velum interpositum
inferior: superior colliculi of the midbrain
what is the thymus?
encapsulated soft bi-lobed organ, the two parts being joined at the midline by connective tissue that merges with the capsule of each lobe; they are occasionally united, so as to form a single mass, and sometimes separated by an intermediate lobe.
What is the specificity of the thymus growth?
-thymus continues to grow until the time of puberty and then begins to atrophy.
It is relatively large in infancy (weighing 25 g at birth) reaching a maximal weight
in adolescence between 12 and 19 years (35 g), and gradually involutes with age (between 20 and 60 years) with progressive fatty replacement (15 g at 60 years of age).
What is the arterial supply to the thymus?
from the inferior thyroid and internal thoracic arteries.
Major blood vessels enter gland at corticomedullary junction.
What is the venous drainage to the thymus?
left brachiocephalic, internal thoracic and inferior thyroid veins.
Large venules run in capsule and leave thymus
What is the lymphatic drainage of the thymus?
parasternal, brachiocephalic and tracheobronchial lymph nodes
What are the relations of the thymus in the neck?
Anterior: investing fascia, behind the Sternohyoidei and Sternothyreoidei.
Posterior: trachea and common carotid arteries. Sometimes it continues in the space between the trachea and the carotid showing also relations with the esophagus and the recurrent laryngeal nerve.
Lateral: common carotid artery
What are the relations of the thymus in the thorax?
Anterior: posterior surface of sternum and insertion of strap muscles in the upper portion.
Posterior: trachea, bronchi, pericardium, on the right side the vena cava, the right brachiocephalic trunk; on the left side with the left brachiocephalic trunk and the aortic arch.
Lateral: phrenic nerves and mediastinic pleura
How is the thymus visible?
thymus visible in CT or MRN axial sections just anterior to ascending aorta + inferior to left brachiocephalic vein.
What are features of the medulla of the thymus?
- Medullary blood vessels not as well protected by epithelial cells,those of corticomedullary junction only partially ensheathed, usually on cortical aspect.
- very variable in size, some may have short lengths of cuboidal endothelium similar to those in lymph nodes + mucosa-associated lymphoid tissue.
What are features of the cortex of the thymus
o pattern of blood flow differs in cortex + medulla.
o Major blood vessels enter gland at corticomedullary junction + pass within each lobe, giving off small capillaries to cortex + larger vessels to medulla.
o Most cortical capillaries loop around at different depths in cortex + join venules at corticomedullary junction;
some continue through cortex + join larger venules running in capsule which leave thymus.
o smaller cortical capillaries : narrow perivascular space, sometimes containing pericytes + other cells, but rarely nerve
What are the relations of the thymus with the thorax in the mediastinum?
- most part of organ lies in superior mediastinum + anterior part of inferior mediastinum.
- extends from 4th costal cartilage upward, as high as lower border of thyroid gland (left lobe).
- covered by sternum + by origins of Sternohyoideus + Sternothyreoideus.
- Below, rests upon the pericardium, being separated from aortic arch + great vessels by layer of fascia.
what are the parathyroid glands?
4 glands
small, yellowish- brown, ovoid structures
(20-50 mg)
have distinct, encapsulated, smooth surface that differs from thyroid gland (more lobular surface) and lymph nodes.
parathyroid gland can be flattened in appearance, especially when in capsule or adherent to thyroid gland.
Where are the parathyroid glands located?
between posterior lobar borders of thyroid gland + its capsule
What is the location specificity of the parathyroid glands’
superior parathyroid glands more constant in location than inferior + usually found midway along posterior borders of thyroid gland (may be higher)
inferior pair more variably situated (related to embryological development), may be
o within fascial thyroid sheath, below inferior thyroid arteries, near inferior lobar poles;
o outside the sheath, immediately above + inferior thyroid artery;
o in thyroid gland near inferior pole.
usually caudal to junction to RLN + inferior thyroid artery.
What is the major arteries irrigating the parathyroid glands?
inferior thyroid artery principal blood supply to parathyroid glands, also superior thyroid artery + small vessels from capsule of thyroid gland.
What is the primary function of the hypothalamus?
maintain homeostasis
Controls basic survival strategies : reproduction, growth + metabolisms, food + fluid intake, attack + defense, control of body temperature, sleep -wake cycle.
How does the hypothalamus send instructions to the rest of the body?
- Via autonomic nervous system: allows ultimate control on blood pressure, heart-rate, breathing, digestion, sweating, all sympathetic + parasympathetic functions.
- via pituitary gland: hypo anatomically + chemically connected to pituitary which pumps hormones (releasing factors) into bloodstream. pituitary = “master gland”, regulates activity of endocrine glands –> hormones vitally important in regulating growth +metabolism.
What is the hypothalamus part of ?
o part of CNS = part of brain controlling endocrine system.
What is the inferior surface of hypothalamus bound by?
optic chiasm, optic tract, posterior edge of mammillary bodies
2 virtual coronal planes divide hypothalamus into 3 sections, what are they?
o ANTERIOR (above optic chiasm, contains preoptic*(medial andlateral),supraoptic, parachiasmatic, paraventricular) o TUBERAL (above + including tuber-pituitary gland, dorsomedial- dorsolateral,ventromedial (m),arcuate (or infundibular) (m)) o POSTERIOR (above + contains Mammillary bodies, Posterior nucleus (m), Tuberomammillary (l),Lateral tuberal,Lateral (l) regions.)
In coronal plane of the hypothalamus, each region comprises a _______ part and a _______ part.
medial, lateral
Which part of the hypothalamus Controls the pituitary gland?
somas of neuroendocrine cells occupy hypophysiotropic area in lower half of preoptic and tuberal regions.
There are 2 classes of neurons in the hypothalamus, what are their names and what do they reach?
o Parvocellular neurons reaching median eminence
o Magnocellular neurons reaching posterior lobe of pituitary gland
What is the Parvocellular neuroendocrine system?
parvocellular neurons
give rise to tuberoinfundibular tract
reaches infundibular capillary bed. AP travelling along these neurons
calcium dependent release of releasing or inhibiting hormones
they will reach the adenohypophysis controlling its secretion pattern.
What is the Parvocellular neuroendocrine system?(hypothalamus)
parvocellular neurons
give rise to tuberoinfundibular tract
reaches infundibular capillary bed. AP travelling along these neurons
calcium dependent release of releasing or inhibiting hormones
they will reach the adenohypophysis controlling its secretion pattern.
What is the magnocellular neuroendocrine system (hypothalamus)?
Magnocellular neurons
give rise to hypothalamo-hypophyseal tract
descends to the neurohypophysis (posterior lobe). 2 hormones released by neurons in supraoptic and paraventricular nuclei: antidiuretic hormone (vasopressin) + oxitocin
What do the hypophysiotropic hypothalamic nuclei do?
transport hypothalamic- stimulating hormones through tuberohypophyseal tract to sinusoids of infundibular stem
Sinusoids then drain into secondary capillary plexus in adenohypophysis.
Antidiuretic hormone (adh) (hypothalamus)
stimulates water uptake from distal convoluted tubules and collecting ducts of kidney, under the control of osmotic pressure. Some adh neurons also secrete corticotropin releasing factor (crh). Withdrawl of adh production –> diabetes insipidus.
