Podcast
Questions and Answers
The pituitary gland is situated within the sella turcica, positioned superior to the intercavernous sinuses and inferior to the diaphragma sellae.
The pituitary gland is situated within the sella turcica, positioned superior to the intercavernous sinuses and inferior to the diaphragma sellae.
False (B)
In cases where sphenoidal air sinuses exhibit extensive development, they invariably extend anteriorly and inferiorly relative to the sella turcica.
In cases where sphenoidal air sinuses exhibit extensive development, they invariably extend anteriorly and inferiorly relative to the sella turcica.
False (B)
The pituitary stalk ascends downwards and forwards connecting the anterior portion of the pituitary gland to the floor of the fourth ventricle.
The pituitary stalk ascends downwards and forwards connecting the anterior portion of the pituitary gland to the floor of the fourth ventricle.
False (B)
Within the pituitary gland, the terms 'adenohypophysis' and 'neurohypophysis' are consistently and precisely synonymous with 'anterior lobe' and 'posterior lobe', respectively, across all clinical and research contexts ensuring seamless interoperability of terminology.
Within the pituitary gland, the terms 'adenohypophysis' and 'neurohypophysis' are consistently and precisely synonymous with 'anterior lobe' and 'posterior lobe', respectively, across all clinical and research contexts ensuring seamless interoperability of terminology.
The adenohypophysis, derived from the neuroectodermal downgrowth of the fourth ventricle floor, encompasses the pars distalis, pars tuberalis, and pars intermedia which collectively constitute the anterior lobe.
The adenohypophysis, derived from the neuroectodermal downgrowth of the fourth ventricle floor, encompasses the pars distalis, pars tuberalis, and pars intermedia which collectively constitute the anterior lobe.
Originating from neuroectodermal differentiation, the neurohypophysis comprises the pars nervosa, infundibular stalk, and median eminence, with the pars nervosa and pars distalis combining topographically to define the posterior lobe of the pituitary gland.
Originating from neuroectodermal differentiation, the neurohypophysis comprises the pars nervosa, infundibular stalk, and median eminence, with the pars nervosa and pars distalis combining topographically to define the posterior lobe of the pituitary gland.
The pars distalis, representing 75% of the pituitary gland, is characterized by a hypovascular nature, with its cellular composition predominantly consisting of chromophils and a sparse population of chromophobes.
The pars distalis, representing 75% of the pituitary gland, is characterized by a hypovascular nature, with its cellular composition predominantly consisting of chromophils and a sparse population of chromophobes.
Within the pars distalis, chromophils are differentiated into acidophils and basophils, whose primary secretions encompass thyroid-stimulating hormone (TSH) and follicle-stimulating hormone (FSH); while acidophils produce growth hormone and prolactin..
Within the pars distalis, chromophils are differentiated into acidophils and basophils, whose primary secretions encompass thyroid-stimulating hormone (TSH) and follicle-stimulating hormone (FSH); while acidophils produce growth hormone and prolactin..
The pars tuberalis, a vestigial extension of the pars intermedia along the pituitary stalk, is recognized for its actively secreting cells producing an array of regulatory hormones influencing circadian rhythms.
The pars tuberalis, a vestigial extension of the pars intermedia along the pituitary stalk, is recognized for its actively secreting cells producing an array of regulatory hormones influencing circadian rhythms.
A pituitary adenoma exerting pressure on the superior aspect of the optic chiasm and the lateral aspects of the optic tracts invariably induces complete bilateral anopia, resulting in total loss of vision in both eyes.
A pituitary adenoma exerting pressure on the superior aspect of the optic chiasm and the lateral aspects of the optic tracts invariably induces complete bilateral anopia, resulting in total loss of vision in both eyes.
The pars tuberalis is situated posterior to the remnant of the pharyngeal downgrowth, preceding the pars intermedia.
The pars tuberalis is situated posterior to the remnant of the pharyngeal downgrowth, preceding the pars intermedia.
The pars intermedia's primary function is the synthesis and secretion of thyroid-stimulating hormone (TSH).
The pars intermedia's primary function is the synthesis and secretion of thyroid-stimulating hormone (TSH).
The pars nervosa contains approximately 1,000,000 myelinated nerve fibers originating from cell bodies in the arcuate and dorsomedial nuclei of the hypothalamus.
The pars nervosa contains approximately 1,000,000 myelinated nerve fibers originating from cell bodies in the arcuate and dorsomedial nuclei of the hypothalamus.
Neurosecretory material, specifically thyrotropin-releasing hormone (TRH) and growth hormone-releasing hormone (GHRH), migrates along the axons at a rate of approximately 15 mm/day to the pars nervosa.
Neurosecretory material, specifically thyrotropin-releasing hormone (TRH) and growth hormone-releasing hormone (GHRH), migrates along the axons at a rate of approximately 15 mm/day to the pars nervosa.
Neurophysins function as enzymatic cofactors essential for post-translational modification of oxytocin and vasopressin, facilitating hormone receptor binding.
Neurophysins function as enzymatic cofactors essential for post-translational modification of oxytocin and vasopressin, facilitating hormone receptor binding.
Pituicytes, prevalent in the pars nervosa, are specialized neurons responsible for action potential propagation and synaptic transmission.
Pituicytes, prevalent in the pars nervosa, are specialized neurons responsible for action potential propagation and synaptic transmission.
Inferior and superior hypophyseal veins, branching directly from the external iliac and middle meningeal arteries, supply the pituitary gland.
Inferior and superior hypophyseal veins, branching directly from the external iliac and middle meningeal arteries, supply the pituitary gland.
Hypophysiotropic hormones are secreted into a venous plexus located exclusively within the pars nervosa; they directly modulate chromophil activity via paracrine signaling.
Hypophysiotropic hormones are secreted into a venous plexus located exclusively within the pars nervosa; they directly modulate chromophil activity via paracrine signaling.
The key distinction between the anterior and posterior pituitary lobes lies in the fact that posterior lobe hormones are synthesized within pituicytes prior to axonal transport and storage.
The key distinction between the anterior and posterior pituitary lobes lies in the fact that posterior lobe hormones are synthesized within pituicytes prior to axonal transport and storage.
The presence of a functional blood/brain barrier within the boundaries of the posterior pituitary and median eminence is critical for selective transport of neurohormones, thus maintaining precise endocrine regulation.
The presence of a functional blood/brain barrier within the boundaries of the posterior pituitary and median eminence is critical for selective transport of neurohormones, thus maintaining precise endocrine regulation.
Flashcards
Pituitary Gland
Pituitary Gland
A small gland at the base of the brain controlling hormones.
Anterior Lobe
Anterior Lobe
The front part of the pituitary, responsible for hormone production.
Posterior Lobe
Posterior Lobe
The back part of the pituitary, storing and releasing hormones.
Adenohypophysis
Adenohypophysis
Signup and view all the flashcards
Neurohypophysis
Neurohypophysis
Signup and view all the flashcards
Growth Hormone
Growth Hormone
Signup and view all the flashcards
Prolactin
Prolactin
Signup and view all the flashcards
Hormone Functions
Hormone Functions
Signup and view all the flashcards
Basophils
Basophils
Signup and view all the flashcards
Infundibulum
Infundibulum
Signup and view all the flashcards
Pars tuberalis
Pars tuberalis
Signup and view all the flashcards
MSH
MSH
Signup and view all the flashcards
Pars intermedia
Pars intermedia
Signup and view all the flashcards
Pars nervosa
Pars nervosa
Signup and view all the flashcards
Oxytoxin
Oxytoxin
Signup and view all the flashcards
Vasopressin
Vasopressin
Signup and view all the flashcards
Neurophysin
Neurophysin
Signup and view all the flashcards
Hypophyseal portal system
Hypophyseal portal system
Signup and view all the flashcards
Chromophils
Chromophils
Signup and view all the flashcards
Transsphenoidal approach
Transsphenoidal approach
Signup and view all the flashcards
Study Notes
Pituitary Gland Anatomy and Function
- Located in the sella turcica of the sphenoid bone, nestled within the skull's base.
- Protected by the diaphragma sellae and surrounding dura mater.
- Optic chiasm sits above and behind the diaphragma sellae, vulnerable to pressure from pituitary tumors.
- Pituitary stalk connects the posterior pituitary to the hypothalamus (third ventricle).
- The infundibulum is the hollowed upper part of the stalk.
- A composite structure of two main parts: anterior and posterior lobes (with different developmental origins). These terms are sometimes used interchangeably with adenohypophysis and neurohypophysis (the latter differentiates based on development).
Anterior Lobe (Adenohypophysis)
- Consists of pars distalis, pars tuberalis, and pars intermedia. (Pars distalis and pars tuberalis often are called the anterior lobe)
- Pars distalis (75% of the gland) is highly vascular.
- Cell types:
- Chromophobes (50%)
- Acidophils (35%): secrete growth hormone and prolactin.
- Basophils (15%): produce ACTH, TSH, FSH, and LH.
- Pars tuberalis surrounds the pituitary stalk; its function isn't fully understood.
- Pars intermedia (small) contains colloid-filled vesicles and likely secretes melanocyte-stimulating hormone (MSH).
Posterior Lobe (Neurohypophysis)
- Develops as neuroectodermal downgrowth from the third ventricle.
- Composed of pars nervosa and the infundibular stalk and the median eminence.
- Largely made up of unmyelinated nerve fibers originating from the supraoptic and paraventricular nuclei of the hypothalamus.
- Neurosecretory material (oxytocin from paraventricular nuclei and vasopressin/ADH from supraoptic nuclei), moves down the axons at 3 mm/day and combines with neurophysin.
- Pituicytes resembling astrocytes are scattered among the nerve fibers.
Blood Supply and Hypophyseal Portal System
- Blood supply comes from superior and inferior hypophyseal arteries.
- Venous blood enters the cavernous and intercavernous sinuses.
- Hypophyseal portal system:
- Unique portal venous channels regulate anterior lobe hormones.
- Hypophysiotropic hormones (regulatory factors) from the median eminence enter the portal vessels.
- These hormones target chromophils in the anterior lobe.
- Posterior lobe receives hormones directly from the hypothalamic cells while the anterior lobe receives hormones from the hypothalamus via the portal system.
- No blood-brain barrier in the posterior pituitary or the median eminence
Surgical Approaches
- Anterior cranial fossa (frontal lobe elevation) and transphenoidal approaches are used to access the pituitary gland.
- Transphenoidal approach is more common, entering through the sphenoidal air sinus.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge on the intricate anatomy and functions of the pituitary gland. Explore parts such as the anterior and posterior lobes, their developmental origins, and their connections to the hypothalamus. This quiz is essential for students studying human anatomy and physiology.
