CONTENTS HISTOLOGY FOR MEDICAL STUDENTS
ATLAS OF HISTOLOGY IMAGES

CONNECTIVE TISSUE

CONNECTIVE TISSUE IS SPECIAL IN
THAT IT IS BUILT FROM CELLS AND INTERCELLULAR MATTER

CLASSIFICATION


LOOSE IRREGULAR CONNECTIVE TISSUE

Specifics:
cell-rich, poor in intercellular matter (fibers and amorphous matter [ground substance])

Localization:
forms stroma of many organs, vascular tunica adventitia; lies underneath epithelia - forms lamina propria of mucous membranes and submucosa, is abundantly represented among muscle cells and fibers


CELLS

INTERCELLULAR MATTER

FIBERS:

GROUND (AMORPHOUS) SUBSTANCE:

ground substance is jelly-like in consistence; cells and fibers are embedded in it


DENSE IRREGULAR CONNECTIVE TISSUE

Specifics: many fibers, few cells, fibers are irregular in orientation

Localization: reticular layer of dermis; periosteum, perichondrium

CELLS

the major component of the relatively scarce cellular population is fibroblasts; occasional mast cells and macrophages may also be found

INTERCELLULAR MATTER

FIBERS: numerous collagen and elastin fibers

GROUND (AMORPHOUS) SUBSTANCE: moderate amounts of glycosaminoglycans and proteoglycans


DENSE REGULAR CONNECTIVE TISSUE

Specifics: many fibers, scarce cells, fibers are regularly oriented - arranged in bundles

Localization: tendons, ligaments, capsules, fasciae, and fibrous membranes

CELLS

very few cells are present, most of them are fibroblasts; some mast cells and macrophages as well

INTERCELLULAR MATTER

FIBERS: in abundance, collagen and elastic; have a regular orientation, form thick bundles (fascicles)

GROUND (AMORPHOUS) SUBSTANCE: glycosaminoglycans and proteoglycans in very limited amounts

TENDON
in tendons collagen fiber fascicles are invested with thin layers of loose irregular connective tissue; the thinnest (first-order) fascicles are surrounded by endotendineum; second-order fascicles are surrounded by peritendineum, the tendon itself is a third-order fascicle

CONNECTIVE TISSUES WITH SPECIAL PROPERTIES

ADIPOSE TISSUE

Specifics:
basically composed of fat cells and thin layers of loose irregular connective tissue

white adipose tissue

Localization: present everywhere

CELLS
white adipose cells (white adipocytes)
cytoplasm is dominated by a single large fat vacuole; cell nucleus and other organelles are pushed by the vacuole to the periphery

there is loose irregular connective tissue between groups of adipocytes

INTERCELLULAR MATTER

FIBERS: small numbers of collagen and elastic fibers

GROUND SUBSTANCE: glycosamino- and proteoglycans in small amounts

brown adipose tissue

Localization: between scapulae, around kidneys and thyroid gland

brown adipose tissue is more widely represented in fetuses, its quantity is greatly reduced after birth


CELLS
brown adipose cells (brown adipocytes)
many small fat droplets are scattered throughout the cytoplasm; nucleus and organelles are in the cell center; multiple mitochondria are present

the brown color of cells is due to significant amounts of iron-containing pigments - cytochromes; in brown adipocyte mitochondria the free energy released from the oxidation of fatty acids and glucose is not stored in the form of ATP, rather it is dissipated as heat; therefore the function of this tissue is heat production and regulation of body's thermal balance

there are also small numbers of fibroblasts and other cell types of loose irregular connective tissue

INTERCELLULAR MATTER

FIBERS: small amounts of collagen and elastic fibers

GROUND SUBSTANCE: glycosamino- and proteoglycans in small amounts

PIGMENTARY TISSUE

Specifics: ordinary loose or dense connective tissue with large numbers of pigment cells

Localization: vascular tunic of the eye, dermis under mammary gland areolae, birthmarks, and nevi

MUCOUS CONNECTIVE TISSUE

Specifics: few cells and fibers, lots of ground substance

Localization: umbilical cord (Wharton's jelly)

CELLS
in general, poorly differentiated fibroblasts in small numbers

INTERCELLULAR MATTER

FIBERS: scarce and thin collagen fibers

GROUND SUBSTANCE: generally contains hyaluronic acid

RETICULAR TISSUE

Specifics: provides a soft structural framework (stroma) for organs of hemopoiesis and immunity

Localization: spleen, lymph nodes, tonsils, lymphoid follicles, and red bone marrow

CELLS

reticular cells (a subtype of fibroblasts) these cells possess processes which they connect to each other through forming thereby a network; other cell types of loose connective tissue are also present in small quantities: macrophages, mast cells, plasma cells, fat cells (adipocytes)

INTERCELLULAR MATTER

FIBERS: reticular fibers - a subtype of collagen fibers, are well stained with silver salts; that's why they are also known as argyrophilic fibers; they form a meshwork

GROUND (AMORPHOUS) SUBSTANCE: extracellular fluid

BONE

CELLS:

INTERCELLULAR MATTER

FIBERS: collagen fibers

GROUND (AMORPHOUS) SUBSTANCE: the predominant component is calcium phosphate mostly in the form of hydroxyapatite crystals and some in amorphous state; small amounts of magnesium phosphate and very scarce glycosaminoglycans and proteoglycans are also found

THERE ARE TWO TYPES OF THE BONE:

fibrous (immature) bone

lamellar (mature) bone

PERIOSTEUM
has 2 layers:
external - fibrous; made of dense irregular connective tissue
internal - cellular (osteogenic); contains many osteoblasts and blood vessels, some osteocytes as well

functions: bone nutrition, longitudinal and transverse growth of bone, its regeneration

ENDOSTEUM
a lining covering a bone from the marrow side, made of loose irregular connective tissue with osteoblasts and osteoclasts in addition to more common cell types of this tissue


CARTILAGE

THREE TYPES OF CARTILAGE ARE DISTINGUISHED: HYALINE, ELASTIC AND FIBROUS

what distinguishes them is primarily intercellular matter composition

CELLS

hyaline cartilage
Localization: trachea and bronchi, articular surfaces, larynx, costosternal junctions

INTERCELLULAR MATTER

FIBERS: collagen fibers

GROUND SUBSTANCE: glycosaminoglycans and proteoglycans

elastic cartilage

Localization: pinna of the ear, corniculate and cuneiform cartilages of the larynx, nasal cartilages

INTERCELLULAR MATTER

FIBERS: elastic and collagen fibers

GROUND SUBSTANCE: glycosaminoglycans and proteoglycans

fibrous cartilage

Localization: attachments of tendons and ligaments to hyaline cartilage, intervertebral disks, semimovable joints, and symphysis

INTERCELLULAR MATTER

FIBERS: parallel fascicles of collagen fibers; more fibers than in other types of cartilage

GROUND (AMORPHOUS) SUBSTANCE: glycosaminoglycans and proteoglycans

intervertebral disk
consists of:

PERICHONDRIUM

has 2 layers:
external - fibrous; made of dense irregular connective tissue
internal - cellular (chondrogenic); contains many osteoblasts and blood vessels

functions: cartilage nutrition, appositional growth, and regeneration

there are no blood vessels in cartilage

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