Bone marrow transplants
Bone marrow plays
an important role. There are two types of bone marrow: the red marrow (also
called myeloid tissue) and the yellow marrow. Erythrocytes, platelets, and most
leukocytes are formed from red marrow. In the yellow marrow a few leukocytes
are made, although what predominates in it are the large fatty blood cells
(which give it its yellowish tone)
From birth most
of the bone marrow is red. However, as a person ages, more and more red marrow
turns yellow in long, flat bones. Bone marrow contains two types of stem cells.
Hematopoietic stem cell grafts increase the number of leukocytes, erythrocytes
and platelets.
Mesenchymatic
stem cells differ in structures that form bone, cartilage, and muscle. Several
diseases affect the bone marrow include infections and malignancies. In
patients who develop neoplasms in the bone marrow (e.g. leukemia), it is
possible to obtain non-malignant cells from the bone marrow of the patient or
another person. The diseased bone marrow can be destroyed by chemotherapy or radiation,
infusing new cells into it. This treatment is known as a bone marrow transplant
Sacred Preganglionic parasimpathic Fibers
In the sacral
region, parasympathetic preganglioneleal fibers form special visceral nerves
(the pelvic spllasic nerves), which originate from the earlier branches of S2
to S4 and penetrate the pelvic extensions of the large
prevertebralvertebralformed plexus around the abdominal aorta. These fibers are
distributed to pelvic and abdominal viscera, mainly along blood vessels. Postganglion
motor neurons are found in the walls of the viscera. In organs of the
gastrointestinal system, preganglional fibers do not have a parasympathetic
motor neuron post-ganglion in the path; instead, the preganglion fibers synap
directly with neurons in the nodes of the enteric system.
Parasympathetic
preganglional fibers in the cranial nerves The parasympathetic parasympathetic
motor fibers in III, VII and IX separate from the nerves and connect with one
of four different nodes, which house post-ganglion motor neurons. These four
nodes are located near the main branches of V. Postganglion fibers leave the
nodes, bind to V branches and are transported to the target organs (salivary
glands, mucous membranes and lacrimal, pupil constrictor muscle and the eye's
ciliary muscle) with these branches. The vagus nerve (X) gives rise to visceral
branches along its path. These branches contribute to plexes associated with
thoracic viscera or the large prevertebral plexus in the abdomen and pelvis.
Many of these plexes also contain sympathetic fibers. When present,
parasympathetic postganglion neurons are found on the walls of target viscera.
Visceral
sensitive inervation (visceral affronts) Visceral sensitive fibers generally
accompany visceral motor fibers. Visceral sensitive fibers accompany
sympathetic fibers Visceral sensitive fibers follow the path of sympathetic
fibers and enter the spinal cord at similar spinal spinal levels. However,
visceral sensitive fibers can also enter the spinal cord
at levels
different from those associated with motor output. For example, visceral
sensitive fibers in the heart may enter higher levels than the T1 spinal cord
level. The visceral sensitive fibers that accompany sympathetic fibers are
mainly involved in the perception of pain. Visceral sensitive fibers accompany
parasympathetic fibers Visceral sensitive fibers accompanying parasympathetic
fibers are mainly transported by IX and X and by spinal nerves from S2 to S4.
The visceral sensitive fibers of the IX carry information from chemiorreceptors
and baroreceptors associated with the walls of the main arteries of the neck,
as well as receptors in the pharynx. The visceral sensitive fibers of the X
include those of cervical viscera and the main vessels and viscera in the chest
and abdomen. The visceral sensitive fibers of the pelvic viscera and the most
distal parts of the colon are transported by S2 to S4. Visceral sensitive
fibers associated with parasympathetic fibers are mainly involved in the
transport of information to the CNS on the state of normal physiological
processes and reflex activities. The enteric system The enteric nervous system
consists of motor and sensory neurons and their support cells, which form two
interconnected plexus, the mienteric and submucosannervous plexus,within the
walls of the tract gastrointestinal). Each of these plexes consists of:
Ganglios, which
house neural bodies and their associated cells.
• You make nerve
fibers, which pass between the nodes and from the nodes to the surrounding
tissues.
Neurons in the
enteric system derive from neural crest cells originally associated with the
occipitocervical and sacral regions. Interestingly, it is noted that there are
more motor neurons in the enteric system than in the spinal cord itself.
Motor and sensory
neurons within the enteric system control reflected activity within and between
parts of the gastrointestinal system. These reflexes regulate peristalsis,
secretory motor activity and vascular tone. These activities may take place
independently of the brain and spinal cord, but they can also be modified by
incoming information of preganglion parasympathetic and sympathetic
post-ganglion fibers. Sensitive information originating in the enteric system
is brought back to the CNS by visceral sensitive fibers.
