Ct Proper-types and Distribution

8/6/2019 Ct Proper-types and Distribution

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Department of Natural SciencesUniversity of St. La Salle


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1.LOOSE CT esophagus, vagina, urinary bladder

Encountered in almost every microscopic

section of the body, it is the packing andanchoring material; binds other tissues and

organs together; allows a degree of mobility

between these parts due to its flexibility.

Found beneath thetunica propria of

organ cavities

Fibers are loosely

arranged in ameshwork as in the

loose areolar or

fibro-elastic types


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Collagenous and elastic fibers are both present

forming a loose, continuous and branching

meshwork; reticular fibers few and inconspicuous. Fibroblasts, macrophages, mast cells are relatively

very few and may include any or all of the different

varieties.

Ground substance is

fluid like, containingmany spaces capable

of becoming enlarged

and distended with

fluid.

These spaces or

areola is a synonym

for loose CT.

Richly supplied with blood vessels, lymphatics,

nerves.


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2.DENSE CT- has compactly

or closely packed fibers;

subdivided into:Dense regular:

a.Dense fibrous (white or

collagenous) CT- tendons

Found wherever firmness

and resistance are needed

in the body, such as in

tendons, flat sheets, cornea, fasciae and aponeurosis.

The fibers are oriented in a consistent pattern to meet

specific mechanical requirements. The predominant elements are oriented collagen

bundles with few, small blood vessels.

Ground substance is scanty in amount.

Blood vessels and nerves are found in CT sheaths.


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In tendons, each bundle is composed of a large

number of fibrils covered by a small amount of loose

CT, termed the endotendineum. Generally, several primary bundles are grouped

together into secondary fascicles bounded by a

coarser type of CT, the peritendineum.

The tendon is composed of a number of fascicles

ensheathed by thick CT called the epitendineum. Few, scattered fibroblasts

are found between the

layers of collagen.

Cell bodies appear rod-

shaped, but rectangular,

triangular or trapezoid in

surface view due to

pressure from the bundles of fibers.

In tendons, these are called tendon cells.


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Dense irregular- skin

Found typically in the dermis

of the skin, capsules of manyorgans, tendon sheaths and

nerves, in parts of the urinary

tract.

Essentially the same as the

loose type except that thefibers are thicker, woven into a compact feltwork

accompanied by extensive elastic networks.

Due to the compact arrangement of its fibers, this

tissue is stronger and offers more resistance than theloose variety.

Cells are located among the fibers. Macrophages are

easily identified by vital dyes; undifferentiated

mesenchymal cells are found along the small vessels.


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Form variants of loose CT. One type maybe transformedinto another depending on changes in local conditions so

that this classification should not be taken strictly.

1.RETICULAR CT- stroma of liver, bone

marrow, spleen, lymph nodes, thymus

Composed of typeIII

collagen; thesefibers are very fine, arranged in

slender bundles which anastomose

forming a delicate lattice network.

The stellate reticular cells are have

long cytoplasmic extensions that join other cells;mesenchyme cells may become actively phagocytic or

remain fixed as primitive reticular cells

Has a large population of resident macrophages adhering

to fibers; a few plasma cells, RBC and WBC are present.

CONNECTIVE TISSUE WITH SPECIAL PROPERTIES


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2. EMBRYONIC CT- uterus

A young form of CT occurring

in fetal life; during regenerationof adult destroyed CT areas

(uterine mucosa); dental pulp

and in certain tumors.

In the uterus, the tissue is

found in the tunica propria(corium) immediately beneath

the columnar epithelium lining of the uterus.

Very cellular, mostly fibroblasts of the spindle and

stellate variety, or the undifferentiated mesenchymal

type. Some blood cells and phagocytes are present. CT

fibers are obscured by coagulated ground substance.

This CT is highly vascular, blood vessels are numerous,

fully formed, containing non-nucleated RBC.


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3. MUCOUS CT- Whartons jelly of umbilical cord

Transient type of tissue that appears in the

development and differentiation of CT Found in the embryo, especially under the skin. In

adult animals, it is limited to the dermis and

hypodermis.

Fibroblasts, a few macrophages and lymphoid

wandering cells are present; fibers are thin,collagenous, increasing in number as the fetus

ages.

Very abundant, soft, jelly-like homogenous ground

substance. Residue contains granules and fibrillar precipitates

when fixed and exhibiting the staining reactions of

mucin.

It stains metachromatically with toluidine blue.


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In the umbilical cord, a

portion of the periphery

of the specimen far from

the 3 big umbilical

vessels will show a mass

of mucous CT called the

Whartons jelly which is

devoid of blood vessels. The specimen is

surrounded by the

amnion which is lined by

a single layer of

cuboidal cells. The CT fibers appear

indistinct showing the

coagulated gelatinous

ground substance.

Mucous tissue of an embryo showing

fibroblasts immersed in a very loose

extracellular matrix composed mainly of

molecules of the ground substances.


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4.ADIPOSE- skin, tongue

Stores fat, provide insulation against heat loss, and

mechanical support in certain regions of the body Plays an important role in maintaining a stable supply

of fuel by accumulating lipid in periods of excess food

intake and releasing fatty acids in periods of fasting.

Widely distributed as fat depots (e.g.panniculus adiposus of the belly and

buttocks in subcutaneous tissue,

yellow bone marrow, mesentery and

omenta) and may exhibit regional

differences in amount as influencedby certain factors like age and sex.

In the nervous system, eyelids, lungs

and penis, adipose tissue is absent.


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In the skin or tongue,

adipose CT can be

recognized readily

by the presence of

rounded clear spaces.

The clear spaces

represent the adipose

ghost cells, the fatcontent of which has

been washed away during the preparation of the slide.

These are closely spaced, separated by the thin

fibrous strands of both collagenous and elastic fibers,

pushed aside by expanding fat cells duringdevelopment to form the fibrous septa separating fat

lobules.

Within these septa are located other types of CT cells

and blood vessels.


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Two types are present:

Unilocular yellow or white

adipose tissue comprise the

bulk of body fat

Multilocular brown variety are

abundant in hibernating

species and newborn human

infants.


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Unilocular adipocytes can generate benign tumors

(lipomas), or malignantliposarcomas. Hibernomas

are relatively rare. In the multilocular type, mitochondria have a

transmembrane protein called thermogenin which

permits proton-motive backflow without passing the

ATP-synthetase system.

This releases heat that warms the body. It is notablethat in obese individuals, thermogenin is reduced in

quantity.

Obesity in adults may result from dietary excess,

resulting to an excessive accumulation of fat in

unilocular cells that become larger than usual

(hypertrophic obesity); or from an increase in the

number of adipocytes (hyperplastic obesity).

The latter typically occur in overnourished infants.


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Hormones that affect adipose tissues:

1.Insulin- increases uptake of glucose by adipocytes and

synthesis of triglycerides from carbohydrates2.Epinephrine, ACTH, glucagon, growth hormone,

thyroxine- promote varying degrees of lipolysis of

stored lipids and release of fatty acids.

ACTH results to localized hypertophy

of adipocytes in lower cervical regioncausing the buffalo hump condition.

3.Estrogens- influence pattern of

distribution of adipose tissue in females

Neural (sympathetic nerves of ANS) or humoral

mechanisms mobilize fats when the body issubjected to fasting periods or severe cold.

These factors stimulate adenylate cyclase,

activating the enzyme triglyceride lipase,

which breaks down triglyceride droplets.


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In general, adipocytes synthesize and store triglycerides.

In the fed state, an insulin:glucagon ratio stimulates

adipocytes to produce the following reactions:

a.Secrete lipoprotein lipase (LPL) into the capillaries of whiteadipose tissue. LPL catalyzes the digestion of triglycerides

(via VLDL and chylomicrons) into FA and glycerol. The former

enter the adipocyte to be stored; the latter travels to the liver.

b.Uptake and metabolize glucose and use it for energy and as a

source of the glycerol moiety of the stored triglycerides.


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In the fasted state, a decreased insulin: glucagon ratio and

epinephrine stimulate adipocytes to begin lipolysis due to

increased levels of cAMP which activate hormone-sensitive

lipase. This catalyzes the cleavage of FA from triglycerides.

The FA are used for ATP synthesis, and converted in the liver toketone bodies. The glycerol is used as a source of carbon for

gluconeogenesis.

Adipocytes secrete a hormone called leptin that has an anorexic

action . The action of the LEP gene is mediated through satiety

centers in the hypothalamus where their receptors are found.


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Hormones and Appetite

Produced byadipose (fat)tissue, leptin

suppressesappetite as its level

increases. When

body fat

decreases,

leptin levels fall,

and appetiteincreases.

Leptin

PYY

Insulin

Ghrelin

Secreted by the stomachwall, ghrelin is one of the

signals that triggers

feelings of hunger as

mealtimes approach. In

dieters who lose weight,

ghrelin levels increase,which may be onereason its so hard to

stay on a diet.

The hormone PYY,

secreted by the smallintestine after meals,

acts as an appetite

suppressant that

counters the appetite

stimulant ghrelin.

A rise in blood sugar

level after a mealstimulates the

pancreas to secreteinsulin. In addition to its

other functions, insulin

suppresses appetite by

acting on the brain.


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Ct Proper-types and Distribution