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Showing posts with label Organ. Show all posts
Showing posts with label Organ. Show all posts

Wednesday, April 14, 2021

Hypopituitarism and Non-Functioning Pituitary Adenomas

Hypopituitarism and Non-Functioning Pituitary Adenomas


Hypopituitarism and Non-Functioning Pituitary Adenomas
Non-functioning pituitary adenomas
Non-functioning pituitary adenomas (NFPAs) are bioc cally inert tumours. They usually present with the physical effects of a pituitary mass lesion (e.g. visual field loss, headache and hypopituitarism) or, increasingly, when discovered incidentally on routine brain MRI (‘pituitary incidentalomas’). Surgical decompression is indicated if there is a visual field defect or if the lesion is close to the optic chiasm.
The usual route for removal is trans-sphenoidally, although trans-cranial surgery is occasionally needed. NFPAs can cause hypopituitarism by compressing the normal gland, which requires endocrine replacement. Histologically, NFPAs can have positive immunostaining for inactive LH and FSH, but they do not secret bioactive hormones. Patients with significant postoperative residual tumour may require radiotherapy.

Hypopituitarism And Non-Functioning 5 Pituitary Adenomas

Hypopituitarism
Causes
Hypopituitarism has several causes, either congenital (from pituitary transcription factor defects) or acquired. Acquired hypopituitarism is most commonly caused by the presence of a pituitary tumour. Other acquired causes include inflammatory and infiltratitive disorders, traumatic brain injury and radiotherapy (Figure 5.1). In patients with hypopituitarism and a large empty pituitary fossa on MRI, it is important to enquire about a previous history of severe headache, as this may reflect missed pituitary apoplexy (Chapter 36).
3D NEURONAL STRUCTURE AND NEUROHISTOLOGY

3D NEURONAL STRUCTURE AND NEUROHISTOLOGY


3D NEURONAL STRUCTURE AND NEUROHISTOLOGY
3D NEURONAL STRUCTURE AND NEUROHISTOLOGY
        A. Spinal cord lower motor neuron. Nissl substance (rough endoplasmic reticulum) stains purple. The nucleolus is stained in the clear nucleus. Cresyl violet stain.
B.Cerebellar Purkinje neurons. Large dendrites branch from the cell body. Intraneuronal neurofibrils and background neural processes (neuropil) stain densely. Silver stain.
GLIAL CELL TYPES

GLIAL CELL TYPES


GLIAL CELL TYPES
Astrocytes provide structural isolation of neurons and their synapses and provide ionic (K+) sequestration, trophic support, and support for growth and signaling functions to neurons. Oligodendroglia (oligodendrocytes) provide myelination of axons in the CNS.
ASTROCYTE BIOLOGY

ASTROCYTE BIOLOGY


ASTROCYTE BIOLOGY
Astrocytes are the most abundant glial cells in the CNS. They arise from neuroectoderm and are intimately associated with neural processes, synapses, vasculature, and the pial-glial membrane investing the CNS. Astrocytes in gray matter are called protoplasmic astrocytes, and in white matter they are called fibrous astrocytes.
MICROGLIAL BIOLOGY

MICROGLIAL BIOLOGY


MICROGLIAL BIOLOGY
MICROGLIAL BIOLOGY
Microglial cells are mesenchymal cells derived from yolk sac that come to reside in the CNS. They are a unique resident population with the capacity for self-renewal. Microglia provide constant surveillance of the local microenvironment, moving back and forth up to 1.5 µm/min. Microglial processes can grow and shrink up to 2-3 µm/min. They have a territory 15-30 µm wide, with little overlap with each other. Resting microglia have soma of 5-6 µm diameter, and activated microglia are ameboid in appearance, with soma of approximately 10 µm diameter.
OLIGODENDROCYTE BIOLOGY

OLIGODENDROCYTE BIOLOGY


OLIGODENDROCYTE BIOLOGY
OLIGODENDROCYTE BIOLOGY
Oligodendrocytes are neuroectodermally derived glial cells that have the major role of myelinating central axons. The trigger for myelination may include associated axonal size and signal molecules (such as ATP, K+, glutamate, GABA, and some cell adhesion molecules). 

Tuesday, April 13, 2021

NEURONAL GROWTH FACTORS AND TROPHIC FACTORS

NEURONAL GROWTH FACTORS AND TROPHIC FACTORS


NEURONAL GROWTH FACTORS AND TROPHIC FACTORS

NEURONAL GROWTH FACTORS AND TROPHIC FACTORS
Neuronal growth factors and trophic factors are signal molecules produced by neurons, glia, and target tissues that can influence neuronal differentiation, growth of neurites, establishment of contacts for signaling, maintenance of neural contacts with their central or peripheral targets, and other functions. 
Central Nervous System

Central Nervous System


Central Nervous System
Time period: day 22 to postnatal development
Introduction
Ectoderm is induced by the notochord to form neuroectoderm during neurulation (see Chapter 17). This neuroectoderm in turn produces the neural tube and neural crest cells from which the central nervous system develops. The central nervous system comprises the brain and spinal cord.

Central Nervous System

Spinal cord
The caudal end of the neural tube continues to elongate and form the spinal cord. A lumen through the centre of the spinal cord, the neurocoel (or neural canal), forms by week 9 and will become the central canal. The neurocoel is lined with thickening layers of neuroepithelia known as the ventricular zone (Figure 44.1) or ependymal layer.

ANATOMY PHYSIOLOGY

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