Cui Dongmei. Atlas of Histology: with functional and clinical correlations. 1st ed

Подождите немного. Документ загружается.

CHAPTER 7

■

Nervous Tissue

125

Figure 7-8A. Peripheral sensory receptors.

Axons of the neuron cell bodies in the posterior root

ganglia carry information from sensory receptors in the

skin, muscles, joints, viscera, blood vessels, mesentaries,

and other connective tissues. Sensory receptors associ-

ated with these axons may consist of encapsulated axon

endings, specialized endings around hair follicles, endings

in conjunction with specialized cells (e.g., Merkel cells),

muscle spindles, and specialized regions of axonal mem-

branes termed free nerve endings (see Figs. 6-7A,B and

13-1). Meissner corpuscles and Pacinian corpuscles are

two types of encapsulated endings and are easier to see

using light microscopy than other receptors in the skin.

In these receptors, the axonal membrane is specialized to

change its permeability in response to mechanical pres-

sure (the regions of specialization are indicated by the

thicker blue lines). The connective tissue capsules help to

focus mechanical force on the axonal membrane.

. Lynch &T. Yang

Meissner corpuscle

Basement

membrane

Pacinian corpuscle

Epidermis

Capsule

Myelin

Schwann

cell

Epidermis

Meissner

corpusle

Epidermis

Meissner

corpusle

Dermis

Figure 7-8B. Meissner corpuscle, thick skin of palm.

H&E, 136; inset 360

Meissner corpuscles are encapsulated, quickly adapting

mechanoreceptors that are sensitive to light touch and

low-frequency vibration. They are important for the

sensation of discriminative touch. Meissner corpuscles

are located in the dermal ridges, at the interface of the

dermis and epidermis. Only the nuclei of the capsu-

lar connective tissue cells are visible after H&E stains.

Using special stains, the corpuscle looks like a stack of

pancakes (Schwann cells, Fig. 7-8A) with one or more

axons intertwining among them. The main axons associ-

ated with Meissner corpuscles are large (6–12 μm) and

heavily myelinated, hence their rapid conduction veloci-

ties. Meissner corpuscles are found in all parts of the skin

of the hand and foot, in the lips, and in a number of

other locations but are most concentrated in thick, hair-

less (glabrous) skin.

Pacinian corpuscles

Capsule

Axon

Core

Growth zone

Adipose tissue

Connective tissue

Figure 7-8C. Pacinian corpuscle, thick skin of palm.

H&E, 68; inset 105

Pacinian corpuscles are large, encapsulated structures that

detect very light touch and vibration. They are located

primarily in the hypodermis of the palms of the hands

and ﬁ ngers and the soles of the feet but are also found in

other areas of skin as well as in the periostea and mes-

entery. They are much larger than Meissner corpuscles,

sometimes reaching 2 mm in length (note different mag-

niﬁ cation). Pacinian corpuscles consist of a specialized

zone of axonal membrane that is exquisitely sensitive

to pressure (Fig. 7-8A) surrounded by a layered cellular

structure that consists of a central core immediately sur-

rounding the axon, an intermediate growth zone, and an

outer capsule. Around 60 to 100 layers are formed by

very thin cells that overlap at their edges, giving the Pacin-

ian corpuscle the appearance of an onion when sectioned.

This sample is from the hypodermis of the skin.

CUI_Chap07.indd 125 6/2/2010 6:32:35 PM

126

UNIT 2

■

Basic Tissues

Central Nervous System

Figure 7-9A. Spinal cord. Myelin stain, 7

In this section through an upper thoracic level of the spinal

cord (Fig. 7-4), the white matter (ﬁ ber pathways) has been

stained dark brown with a myelin stain. The gray matter

is a region of densely packed neuron cell bodies, and this

stain has consequently left the gray matter in the center of

the cord relatively unaffected. The anterior horn of the gray

matter contains motor neurons that innervate muscle ﬁ bers;

the posterior horn contains interneurons in both sensory

and motor pathways. The white matter consists of nerve

ﬁ bers carrying sensory information from receptors in skin

and muscles up to the brain (e.g., the gracile fasciculus) or

nerve ﬁ bers carrying motor information down from the

brain to interneurons and motor neurons in the gray matter

of the spinal cord (e.g., the corticospinal tract). The red rect-

angle indicates the position of the tissue in Figure 7-9B that

has been stained with a Nissl stain for neuron cell bodies.

White matter

(axons)

Gray matter

(neuron cell bodies)

Posterior

Gracile

fasciculus

Posterior

horn

Corticospinal

tract

Gray matter

Glia cell nuclei

Capillary

Axon

White matter

Neuron cell bodies

Figure 7-9B. Spinal cord. Nissl stain, 136

Nissl stains, such as thionin or cresyl violet, react with

nucleic acids (RNA, DNA) and, therefore, stain the rough

endoplasmic reticulum, nuclei, and nucleoli of neurons.

This renders the neuron cell bodies visible, along with the

nuclei of glial cells and nuclei of epithelial cells in blood

vessels. The large cell bodies in this section belong to motor

neurons in the anterior horn of the spinal cord (red rect-

angle in Fig. 7-9A). Also visible are the nuclei of glial cells

(astrocytes and oligodendrocytes) in the gray matter on

the left side of the picture and in the white matter on the

right side of the picture (small arrows). It is important

to keep in mind when looking at myelin-stained sections

such as in Figure 7-9A that the light-colored areas, where

nothing seems to be stained, are in fact ﬁ lled with neuron

cell bodies similar to the ones illustrated here.

Figure 7-9C. Neurons in the reticular formation of

the brainstem. NADPH histochemical stain, 68

Neurons use a wide variety of neurotransmitters. In

addition to stains that react with structural components

of a nerve cell, it is possible to use histochemical reac-

tions to visualize the presence of particular neurotrans-

mitters. This photomicrograph illustrates an example of

such a reaction, in which only those neurons that generate

the neurotransmitter nitric oxide (NO) are visualized. In

this case, an enzyme necessary for the synthesis of NO,

NADPH diaphorase, was labeled using a blue chroma-

gen (colored substance). The neurons are colored in their

entirety because NO is a novel neurotransmitter that is not

bound in vesicles as are most neurotransmitters, but rather

is synthesized everywhere in the cell and leaks through the

cell membrane when it is released. It often functions to

modulate the action of other neurotransmitters.

CUI_Chap07.indd 126 6/2/2010 6:32:40 PM

CHAPTER 7

■

Nervous Tissue

127

Figure 7-10A. Cerebral cortex. Nissl stain, 24

The cerebral cortex is a layer of densely packed neurons

about 2 mm thick that forms the surface of the hemi-

spheres of the brain. The cortex is organized into layers

(indicated by red lines and Roman numerals) on the basis

of the size, shape, and packing density of the neurons

in different regions of the cortex. For example, layers II

and IV in this photomicrograph consist of small, tightly

packed neurons (mainly granule cells), whereas layers III

and V consist of larger neurons (mostly pyramidal cells).

This example is taken from the association cortex of the

parietal lobe (red box in inset). Layer I consists predomi-

nantly of horizontally running dendrites and axons; the

nuclei in this region belong to glial cells. The white matter

consists of axons entering and leaving this small region of

cortex and connecting it with other cortical regions, with

subcortical structures such as the thalamus and with the

spinal cord.

Pia

White matter (myelinated axons)

III

CLINICAL CORRELATION

Figure 7-10C.

Alzheimer Disease. Bielschowsky

stain, 272; inset 550

Alzheimer disease is the most common form of

dementia in the elderly (60%–80% of cases). Patients

show progressive memory loss, personality changes,

and cognitive impairments. Pathologically, Alzheimer

disease is characterized by extracellular deposition

of Ab protein (plaques), intracellular neuroﬁ brillary

tangles (inset: N, normal neuron; T, neuron cell body

ﬁ lled with dark-staining tangles), and loss of neurons

and synapses in the cerebral cortex and some subcor-

tical regions. Gross anatomy shows atrophy of the

affected regions. The most prominent theory is that

mutation of genes such as those located on chromo-

some 21 lead to overproduction of Aβ precursor.

There is no cure for Alzheimer disease. Treatments

include pharmaceutical and psychosocial therapies

and supportive caregiving.

Amyloid plaques

Figure 7-10B. Cerebral cortex, pyramidal cells. Golgi

preparation, 136

The most numerous neurons in the cerebral cortex are

pyramidal cells, named for their triangular cell bodies

(singular, soma; plural somata; S in the inset and photo-

micrograph). Pyramidal cells are also characterized by a

long apical dendrite (AD) that extends into layer I and

has many lateral branches; several basal dendrites (BD)

that extend laterally from the base of the soma; and a long

axon (A) that leaves the cortex and extends, in the white

matter, either to some other region of the cortex or to sub-

cortical structures, such as the basal nuclei, brainstem, or

spinal cord. Pyramidal cells are found in layers II through

VI of the cortex but are most obvious in layers III and V.

Somata range in size from 10 to over 50 μm, with the larg-

est located in layer V of primary motor cortex. The sam-

ple shown here is taken from layer III. It includes several

medium pyramidal cells and many small pyramidal cells.

CUI_Chap07.indd 127 6/2/2010 6:32:45 PM

128

UNIT 2

■

Basic Tissues

Figure 7-11A. Cerebellar folium. Nissl stain, 34

The cerebellum (green structure in inset) is a large, complex struc-

ture that lies beneath the posterior portion of the cerebral hemi-

spheres. Its name means “little brain.” It is critical for smooth,

coordinated movements and participates, to a lesser extent, in many

other functions. The structural organization of the cerebellum is

similar to that of the cerebrum in that it consists of white matter,

a cortex, and subcortical nuclei. However, the organization of the

cortex is very different from that of the cerebral cortex. There are

only three layers, the granule cell layer, the Purkinje cell layer, and

the molecular layer. The granule cell layer contains an enormous

number of very small, tightly packed cells and their dendrites. The

Purkinje cell layer, at the interface of the granule cell and molecular

layers, is only one cell deep. The molecular layer contains primarily

axons and dendrites, with only very few neuron cell bodies. The

red rectangle indicates the position of the tissue in this ﬁ gure.

Purkinje cell

Molecular layer

Granule cell

layer

White matter

Molecular layer

Purkinje cell

Granule cell

layer

CLINICAL CORRELATION

Figure 7-11C.

Encephalocele. H&E, 17

In some embryos, the neuroectoderm does not sepa-

rate from the surface ectoderm during early stages of

development. A defect in the calvarium may occur as

the bone of the skull is formed, through which CSF

meninges, and brain tissue may protrude. This case

illustrates immature brain tissue and its meningeal

covering, which have herniated through a bony defect

in the occipital bone. These neuroectodermal tissues

are found directly beneath the dense subcutaneous

connective tissue of overlying skin. Encephaloceles

are most frequently found in the occipital region. In

their several variations, they may contain (1) only CSF

and meninges, (2) CSF, meninges, and brain substance

(occipital lobe or cerebellum), or (3) CSF, meninges,

brain, and part of the ventricular system. The more

elaborate the encephalocele, the more debilitating and

difﬁ cult it is to treat.

Skin

Abnormal

nervous tissue

Meninges

Purkinje cell

bodies (P)

Granule cell

layer (G)

Molecular layer (M)

Granule cell

layer (G)

Purkinje cell

bodies (P)

Figure 7-11B. Cerebellar cortex. Nissl stain, 68, inset 1,

124; inset 2, Golgi, 74

Purkinje cells and granule cells are the most obvious neurons in

the cerebellar cortex. Purkinje cells, among the largest neurons

in the CNS, lie between the granule cell layer and the molecular

layer (inset 1). Purkinje cells have widely branching dendritic

trees that extend through the entire depth of the molecular layer

(inset 2). The dendritic tree of a Purkinje cell is shaped like

a paper fan. The wide part of the “fan” is seen when cutting

across the long axis of a folium (inset 2). The edge of the fan is

seen when cutting parallel to the long axis of the folium (inset 3).

Granule cells (blue, inset 3) send their axons into the molecular

layer in which they divide and run parallel to the long axis of the

folium, making synaptic contact with hundreds or thousands of

Purkinje cell dendrites. Another major element in the basic cer-

ebellar cortex circuitry is the climbing ﬁ ber (red, inset 3). These

axons originate in the inferior olivary nucleus. Each climbing

ﬁ ber encircles the dendrites of a single Purkinje cell. Purkinje cell

axons provide the sole output pathway of the cerebellar cortex.

CUI_Chap07.indd 128 6/2/2010 6:32:51 PM

CHAPTER 7

■

Nervous Tissue

129

CLINICAL CORRELATION

Figure 7-12C.

Meningitis. H&E, 34; inset 147

Meningitis is an inﬂ

ammatory disease of the meninges

that is largely sequestered in the SAS. The inﬂ amma-

tion is usually caused by infection by viruses, bacteria,

or fungal agents. Signs and symptoms include fever,

headache, irritability, photophobia, neck stiffness

(meningismus), vomiting, altered mental status, and

cutaneous hemorrhages (purpura). Complications may

lead to deafness, epilepsy, and hydrocephalus. Patho-

logically, the meningitis affects the pia- arachnoid and

the CSF in the SAS and may extend into the cerebral

ventricles. Characteristic ﬁ ndings include perivascular

cuffs of acute and chronic inﬂ ammatory cells (inset,

from red box), which distend the arachnoid space.

Lumbar puncture (spinal tap) for CSF is an impor-

tant diagnostic tool. Treatment is usually supportive

for viral meningitis and includes antibiotics or other

agents that can cross the blood-brain barrier for bac-

terial or fungal meningitis.

Arachnoid space

filled with

inflammatory cells

and proteinaceous fluid

Pia mater

Spinal cord

white matter

Spinal cord

white matter

Pia mater

Arachnoid

membrane

Arachnoid space

filled with

inflammatory cells

and proteinaceous fluid

Figure 7-12A. Dura mater, arachnoid, and pia mater.

The leathery outer meningeal layer, the dura mater (or dura),

consists of elongated ﬁ broblasts and large amounts of extracel-

lular collagen. It is tenuously attached to the arachnoid barrier

layer; there is no “subdural space” in the normal state. The dura

is tenaciously attached to the skull at the base of the brain and

at the sutures and is less tightly adherent to the skull in other

regions. The arachnoid barrier layer consist of two to three

layers of cells that are attached to each other by many con-

tinuous tight junctions, hence its “barrier” nature to CSF. The

sub arachnoid space (SAS) is located between the arachnoid

and the pia, contains blood vessels and CSF, and is traversed by

arachnoid trabeculae. The pia mater generally consists of one

to two layers of ﬂ attened ﬁ broblasts that are adherent to the

surface of the brain and spinal cord. Blood vessels located in the

SAS are frequently covered by thin layers of pia. The interface

between the pia and the nervous tissue is characterized by a glial

limiting membrane (glia limitans), as shown in Figure 7-13A.

J. Lynch

Dura mater

Arachnoid

barrier cells

Pia mater

Nervous tissue

(brain or spinal

cord)

Subarachnoid

space

Blood

vessel

Arachnoid

trabeculum

Posterior horn

Spinal cord

white matter

Pia

Blood vessels

Dura

Epidural space

Spinal cord

white matter

Posterior horn

Blood vessels

Pia

Arachnoid

Subarachnoid

space

Posterior root

of spinal nerve

Figure 7-12B. Spinal meninges in the region of the

posterior roots. H&E, 34

At spinal levels, the dura mater forms a tubular sac enclosing

the spinal cord. However, in contrast to the cranial dura, which

adheres to the skull, the spinal dura is separated from the ver-

tebral bodies by an epidural space. Both the spinal and the cra-

nial dura consist of many elongated ﬁ broblasts and abundant

extracellular collagen. The arachnoid barrier cell layer is basi-

cally the same at cranial and spinal levels. In the normal state,

the barrier cell layer is attached to the dura, although only

weakly. There is no naturally occurring subdural space; what

appears to be a space here is a tissue preparation artifact. The

pia mater on the cord is continuous with the epineurium on

the posterior root, the latter representing a part of a peripheral

nerve. The SAS is located between the pia and the arachnoid

and at this point contains the posterior roots.

CUI_Chap07.indd 129 6/2/2010 6:32:56 PM

130

UNIT 2

■

Basic Tissues

Figure 7-13A. Types of glial cells.

Glial cells (also called neuroglia or glia) are nonneuronal cells that

aid in transferring nutrients from capillaries to neurons, main-

tain the blood-brain barrier, regulate the intercellular environ-

ment, provide myelin insulation for axons, provide mechanical

support to neurons, act as phagocytes to remove pathogens and

dead neurons, play a role in presenting antigens in the immune

system, and perform numerous other functions. Recent evidence

suggests that glial cells even participate in some aspects of synap-

tic transmission. It is thought that there are as many as 10 times

the number of glial cells as neurons in the nervous system. The

major types of CNS glial cells are astrocytes (described below),

oligodendrocytes (which produce myelin), and microglia (which

act as phagocytes and elements of the immune system). Other

glialike cells include radial glia cells and ependymal cells in the

CNS and Schwann cells and satellite cells in the PNS.

J. Lynch

Pia

Astrocyte

Glia limitans

Capillary

Oligodendrocyte

Microglia

Pyramidal

cell

Protoplasmic astrocyte

Pyramidal cells

Cerebral cortex, layer III

Fibrous astrocyte

in cerebellar white matter

Figure 7-13B. Astrocytes. Golgi preparations, upper left,

136; lower right, 204

Astrocytes are found throughout the CNS. Astrocyte processes

called end-feet form contacts with capillaries that help produce

the blood-brain barrier and form contacts on neurons that play a

role in supplying nutrients to these cells. Astrocytes regulate the

ionic composition and pH of the extracellular environment and

secrete various neuroactive substances. Astrocyte end-feet form

the glia limitans, a coating of the inner surface of the pia mater

that surrounds the brain and spinal cord (Fig. 7-13A). Finally,

astrocytes play an important role in neurotransmitter metabo-

lism and in the modulation of synaptic transmission. There are

two types of astrocytes. Protoplasmic astrocytes, in gray matter,

have short, thick processes that are densely clustered and highly

branched, giving them a cloudlike appearance. Fibrous astro-

cytes, in white matter, have long, thin processes with relatively

few branchings. The two types of astrocytes have similar func-

tions but differ in some special properties.

CLINICAL CORRELATION

Figure 7-13C.

Glioblastoma. H&E, 68; inset 84

Glioblastoma (a form of astrocytoma) is a highly malignant

tumor that arises in the brain from neoplastic astrocytes. Sev-

eral features of this tumor help the pathologist arrive at the

diagnosis. In the center of this micrograph, the tumor cells

are necrotic. At the edges of the zone of necrosis, nonnecrotic

tumor cells align themselves in a striking parallel array, like

the pickets of a fence. This conﬁ guration is called palisading

(arrows, inset). Beyond the area of palisading, living tumor

cells commonly surround complex abnormal vascular struc-

tures (glomeruloid vascular structures) that resemble the glom-

eruli of the kidney in their tortuous arrangement of capillar-

ies. Increased mitosis among the viable tumor cells also aids

in the diagnostic process. Increasing the life span of patients

with glioblastoma is currently an area of intensive research.

Live

tumor cells

Zone of

palisading

Necrotic

tissue

Necrotic

tissue

Necrotic

tissue

Live

tumor cells

Zone of

palisading

Abnormal

capillaries

Abnormal

capillaries

CUI_Chap07.indd 130 6/2/2010 6:32:59 PM

CHAPTER 7

■

Nervous Tissue

131

J. Lynch

Preganglionic cholinergic fibers

Postganglionic cholinergic fibers

Postganglionic adrenergic fibers

Eye

Lacrimal gland

Submandibular gland

Sublingual gland

Parotid gland

Oral mucosa

NOTE: In addition to the other

all chain ganglia include

connections diagramed above,

postganglionic fibers that go to

the skin (e.g., sweat glands)

and to blood vessels in the

these three ganglia.

body wall, as indicated in

Ciliary ganglion

Pterygopalatine ganglion

Submandibular ganglion

Otic ganglion

III

VII

Larynx,

trachea,

bronchi

Heart

Liver

Pancreas

Intestines

Myenteric plexus,

submucosal plexus

Pelvic

splanchnic

nerves

Stomach

Kidney

Bladder

Celiac

ganglion

Sympathetic

chain ganglia

Inferior

mesenteric

ganglion

Adrenal

Superior

mesenteric

ganglion

Cervical

ganglia

Genitalia

Sympathetic Division Parasympathetic Division

Figure 7-14. Overview of the autonomic nervous system (continues on page 131).

Autonomic Nervous System

CUI_Chap07.indd 131 6/2/2010 6:33:01 PM

132

UNIT 2

■

Basic Tissues

Figure 7-15A. Sympathetic ganglion. H&E, 272; inset

520

This section from a sympathetic chain ganglion shows small

to medium-sized visceromotor neuron cell bodies that give rise

to postganglionic axons. These neurons receive synapses from

preganglionic sympathetic axons that originate in the lateral horn

of the thoracic and upper lumbar spinal cord. The preganglionic

axons are myelinated; the postganglionic axons are unmyeli-

nated. These motor neurons are multipolar (in contrast to the

unipolar sensory neurons in the posterior root ganglia), although

the dendrites are not visible in this H&E stain. The sizes of the

cell bodies are more uniform than in the sensory ganglia, and

the cell bodies and axons are distributed more evenly across the

ganglia rather than being grouped into clumps as in the sensory

ganglia. The satellite cells are not distributed so evenly around

the neuron cell bodies as they are in the sensory ganglia.

Nucleolus

Nucleus

Cytoplasm

Axons

Satellite

cell nucleus

Sympathetic

motor neuron

Sympathetic

motor neuron

Axons

Satellite

cell nucleus

Cytoplasm

Nucleus

Nucleolus

Longitudinal smooth

muscle layer

Myenteric plexus

Circular smooth

muscle layer

Circular smooth

muscle layer

Myenteric plexus

Longitudinal smooth

muscle layer

Figure 7-15B. Myenteric plexus (Auerbach plexus).

H&E, 136; inset 300

The enteric division lacks the discrete, encapsulated ganglia that

characterize the sympathetic division. Its visceromotor neurons

are distributed in a network of plexuses that are distributed

within the walls of the gastrointestinal tract. Most neurons in

the enteric division are found in the myenteric and submucosal

plexuses. The myenteric plexuses lie between the circular smooth

muscle layer and the longitudinal smooth muscle layer of the

intestine (see Chapter 15 “Digestive Tract”; see also Chapter 6,

“Muscle,” Fig. 6-10B). These plexuses are clusters of parasym-

pathetic postganglionic motor neurons; sensory neurons, which

receive input from chemoreceptors and mechanoreceptors in

the intestinal wall; and local circuit neurons (interneurons).

Interneurons can process neural signals within a plexus and can

also mediate the coordination of multiple plexuses. (Inset: P,

multipolar postganglionic motor neuron; S, satellite cell.)

Figure 7-14. Overview of the autonomic nervous system (Continued).

The ANS is composed of three divisions: sympathetic, parasympathetic, and enteric. The sympathetic and parasympathetic divi-

sions function under direct CNS control; the enteric division functions somewhat more independently. The sympathetic division

includes preganglionic neurons with cell bodies in the lateral horn of the thoracic and upper lumbar spinal cord (Fig. 7-4). Some of

these neurons synapse on postganglionic neurons in the sympathetic chain ganglia (Figs. 7-4 and 7-15A); others continue past these

ganglia and synapse in prevertebral sympathetic ganglia (e.g., celiac ganglion, mesenteric ganglia) near the organs to be innervated.

Postganglionic neurons send axons to internal organs, glands, and blood vessels. Effects of sympathetic activity include increas-

ing cardiac output, blood pressure, and bronchial diameter; decreasing gut peristalsis; and, in general, preparing the individual for

strenuous activity, sometimes called the “ﬁ ght-or-ﬂ ight” reaction. The parasympathetic division has a markedly different organiza-

tion. Preganglionic ﬁ bers originate in brainstem nuclei associated with cranial nerves III, VII, IX, and X and in the sacral parasym-

pathetic nucleus (which occupies a position in the sacral spinal cord similar to that of the lateral horn in the thoracic cord). The

parasympathetic preganglionic ﬁ bers that supply the head region synapse in discrete ganglia (Fig. 7-14) and the postganglionic ﬁ bers

end in glands and smooth muscle. By contrast, parasympathetic preganglionic ﬁ bers that travel in cranial nerve X (vagus nerve)

and the pelvic splanchnic nerves send signals to the viscera and blood vessels within the body cavity. These ﬁ bers do not synapse in

discrete ganglia but rather in small plexuses of postganglionic cell bodies that lie in or adjacent to the walls of their target organs

(Figs. 7-15B and 7-16A). The general effect of parasympathetic activity is the opposite of sympathetic activity and tends to return

the internal organs and cardiovascular system to a baseline level of function. The enteric division consists of a vast number of neu-

rons arranged in a network of plexuses in the walls of the gut. Some of these plexuses are shared with the parasympathetic division.

The activity of the enteric division is modulated in a general way by the sympathetic and parasympathetic divisions, but it is able to

act independently and reﬂ exively to move boluses of food substances through the gastrointestinal tract by peristaltic action and to

control absorption, local blood ﬂ ow, and secretion in response to the chemical composition of the bolus.

CUI_Chap07.indd 132 6/2/2010 6:33:02 PM

CHAPTER 7

■

Nervous Tissue

133

Figure 7-16. Submucosal plexus (of Meissner). H&E,

136; inset 453

The submucosal plexuses (of Meissner) are located in the

submucosal layer of the intestine (see Chapter 15, “Diges-

tive Tract”). These plexuses are similar to the myen-

teric plexuses in that they are unencapsulated clusters

of parasympathetic postganglionic motor neurons; sen-

sory neurons, which receive input from chemoreceptors

and mechanoreceptors in the intestinal wall; and local

circuit neurons (interneurons). The postganglionic motor

neurons may innervate smooth muscle to either increase

or decrease muscle activity and may also innervate secre-

tory cells in the walls of the intestine.

Submucosal

plexus

Submucosal

connective tissue

SYNOPSIS 7-1 Pathological and Clinical Terms for the Nervous System

Ataxia ■ : Inability to coordinate the muscles properly in the execution of a voluntary movement.

Gliosis

■ : The multiplication of astrocytes as a response to injury in the brain, as exempliﬁ ed by the feltwork of astrocytic

cell bodies and processes in a demyelinated plaque of MS.

Glomeruloid vascular structures

■ : Complex arrays of capillaries that resemble the glomeruli of a kidney, are another

hallmark of the glioblastoma.

Neuroﬁ brillary tangle

■ : The helical arrangement of abnormally phosphorylated neuroﬁ laments found in many hippocampal

and cortical neurons of an Alzheimer patient.

Neuropathy

■ : A disease involving the cranial or spinal nerves.

Onion bulb

■ : After repeated cycles of demyelination and remyelination, thin layers of Schwann cell cytoplasm form

concentric circles around a central axon. The appearance of the structure resembles a cross section of an onion bulb and

its nested leaves.

Palisading

■ : The alignment of viable tumor cells at the edge of a necrotic focus in glioblastoma, a diagnostic hallmark of

this grade 4 (most malignant) astrocytoma, a family of glial tumors derived from the astrocyte.

Plaque

■ : This word indicates a lesion, in several pathological contexts. (1) An atherosclerotic plaque is the hard, calciﬁ ed

buildup of fatty material in large arteries, such as the coronary arteries or aorta. (2) A neuritic plaque is the extracellular

knot of phosphorylated axons and dendrites, often with a central deposit of amyloid protein, found in great numbers

in brains of patients with Alzheimer disease. (3) In MS, a demyelinated plaque is an irregular zone of axons, often in a

periventricular location, that have lost their sheaths of myelin.

Type of Ganglion Cell Body

Arrangement

Cell Body

Characteristics

Satellite Cells Synapses in

Ganglion

Posterior root

(sensory)

Arranged into groups

within ganglion, cell

bodies variable in size

Round cell body,

central nucleus

Complete capsule of

satellite cells

No synapses

Autonomic

( visceromotor)

Evenly distributed

within ganglion,

uniform in size

Multipolar cell body,

eccentric nucleus

Incomplete capsule of

satellite cells

Numerous synaptic

contacts

TABLE 7-1 Comparison of Posterior Root and Autonomic Ganglia

CUI_Chap07.indd 133 6/2/2010 6:33:05 PM

134

Blood and

Hemopoiesis

Peripheral Blood Cells

Introduction and Key Concepts for Peripheral Blood Cells

Figure 8-1 Overview of Peripheral Blood Cell Types

Erythrocytes and Platelets

Figure 8-2A Erythrocytes (Red Blood Cells)

Figure 8-2B Platelets (Thrombocytes)

Figure 8-2C Clinical Correlation: Sickle Cell Anemia

Figure 8-3A Erythrocytes, Small Artery

Figure 8-3B Erythrocytes and a Platelet in a Small Blood Vessel

Leukocytes: Agranulocytes

Figure 8-4A Lymphocytes

Figure 8-4B Monocytes

Figure 8-4C Clinical Correlation: Chronic Lymphocytic Leukemia

Leukocytes: Granulocytes

Figure 8-5A,B Neutrophils

Figure 8-6 Neutrophil Phagocytosis

Figure 8-7A Eosinophil

Figure 8-7B Basophil

Synopsis 8-1 Life Spans, Counts, and Sizes of Blood Cells

Figure 8-8 Eosinophil in Connective Tissue

Table 8-1 Leukocytes

Hemopoiesis

Introduction and Key Concepts for Hemopoiesis

Figure 8-9A A Representation of Erythropoiesis

Figure 8-9B Thrombopoiesis

CUI_Chap08.indd 134 6/17/2010 10:19:31 AM