CONNECTIVE TISSUE PROPER

• CONNECTIVE TISSUE PROPER

  •two general subtypes:

  • Loose connective tissue (areolar tissue)
  • dense connective tissue

  •dense irregular connective tissue

  •dense regular connective tissue.
• LOOSE CONNECTIVE TISSUE

  •thin and relatively sparse collagen fibers

  •most numerous cells are fibroblasts

  •comprises a thick layer (the lamina propria) beneath the epithelial lining of the digestive system and fills the spaces between muscle and nerve fibers

  well-vascularized

  •has a delicate consistency; it is flexible and not very resistant to stress.

  -site of inflammatory and immune response
• DENSE CONNECTIVE TISSUE

  •adapted to offer stress resistance and protection

  •Same components found in loose connective tissue, but with fewer cells and a clear predominance of collagen fibers over ground substance.

  •less flexible and far more resistant to stress than loose connective tissue
• DENSE IRREGULAR CONNECTIVE TISSUE

  •contains mostly collagen fibers.

  •Cells are sparse and are typically of a single type, the fibroblast

  •fibers are arranged in bundles oriented in various directions

  •withstand stresses on organs or structures

  •Location:

  • Submucosa
  • Reticular layer of the dermis
  • Organ capsules
• DENSE REGULAR CONNECTIVE

  TISSUE

  •characterized by ordered and densely packed arrays of fibers and cells.

  •they are white in the fresh state and almost inextensible

  •separated by very little ground substance 

  •strong, flexible straps or cords that hold together components of the musculoskeletal system

  •Location:

  • Tendons
  • Ligaments
  • Aponeuroses
• RETICULAR TISSUE

  •reticular cells

  •form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages.

  •Location:

  • Bone marrow
  • Lymph nodes
  • Spleen
• MUCOID TISSUE

  •embryonic type of connective tissue 

  •abundant ground substance composed chiefly of hyaluronic acid, mucoid tissue is jellylike with sparse collagen fibers and scattered fibroblasts

  •Wharton's jelly

  •Location:

  • umbilical cord
  • fetal organs.
• ADIPOSE TISSUE

  • Connective tissue in which adipocytes or fat cells predominate

  •serving as storage depots for neutral fats (triglycerides)

  •key regulators of the body's overall energy metabolism endocrine tissue

  •conducts heat poorly and helps thermally insulate the body

  •fills up spaces between other tissues and helps cushion and keep some organs in place 

  •help shape the body surface
• WHITE ADIPOSE TISSUE

  • Unilocular

  •have a signet-ring appearance

  •surrounded by a thin external lamina containing type IV collagen.

  •energy storage, insulation, cushioning of vital organs, and secretion of hormones.

  •Location:

  • subcutaneous layer of connective tissue
  • mammary fat pad
  • around the kidneys
  • bone marrow and between other tissues, where it fills in spaces.
  • palms of the hands and the soles of the feet,
  • beneath the visceral pericardium
  • orbits around the eyeballs
• BROWN ADIPOSE TISSUE

  • Multilocular

  •principal function is heat production

  •In adults it is found only in scattered areas, especially around the kidneys, adrenal glands, aorta, and mediastinum.

  •very abundant mitochondria

  •large number of blood capillaries in this tissue

  •cytoplasm contains a great number of lipid droplets of various sizes and nuclei are often centrally located
• CARTILAGE

  •an avascular tissue that consists of chondrocytes and an extensive extracellular matrix

  •its firm consistency allows the tissue to bear mechanical stresses without permanent distortion

  •avascular

  •Perichondrium

  • Chondrocytes

  •Isogenous groups

  • Territorial matrix

  • Interterritorial matrix
• Perichondrium

  • a sheath of dense connective tissue that surrounds cartilage in most places, forming an interface between the cartilage and the tissues supported by the cartilage
• Chondrocytes

  • specialized cells that produce and maintain the extracellular matrix
  • located in matrix cavities called lacunae
• Isogenous groups

  • Clusters of chondrocytes
• Territorial matrix

  • region that is more removed from the immediate vicinity of the chondrocytes.
• Interterritorial matrix

  • a region that surrounds the territorial matrix and occupies the space between groups of chondrocytes
• CHONDROGENESIS

  •the process of cartilage development, begins with the aggregation of chondroprogenitor mesenchymal cells to form a mass of rounded, closely apposed cells

  •The dividing cells are typically called chondroblasts and chondrocytes when proliferation has ceased
• HYALINE CARTILAGE

  •the most common of the three forms

  • Resists compression

  • Provides cushioning, smooth, and low-friction surface for joints

  • Provides structural support in respiratory system (larynx, trachea, and bronchi)

  • Forms foundation for development of fetal skeleton

  • endochondral bone formation and bone growth

  • ADULTS

  • EMBRYO

  •type II collagen

  • Homogeneous and semitransparent in the fresh state
• HYALINE CARTILAGE IN ADULTS

  • articular surfaces of movable joints
  • walls of larger respiratory passages (nose, larynx, trachea, bronchi)
  • ventral ends of ribs,
  • epiphyseal plates of long bones
• HYALINE CARTILAGE IN EMBRYO

  • temporary skeleton that is gradually replaced by bone.
• type II collagen

  •most abundant proteoglycan of hyaline cartilage

  aggrecan
• ELASTIC CARTILAGE

  •contains an abundant network of elastic fibers collagen type II

  •elastic material gives the cartilage elastic properties in addition to the resilience and pliability

  •dark bundles distributed unevenly through the matrix.

  •provides flexible support

  •LOCATION

  • Ear
  • Epiglottis
  • Cuneiform cartilage in the larynx
• FIBROCARTILAGE

  •a combination of hyaline cartilage and dense connective tissue

  •Chondrocytes occur singly and in aligned isogenous aggregates

  • Type II collagen

  •Regions with chondrocytes and hyaline matrix are separated by other regions containing bundles of type I collagen and scattered fibroblasts matrix is more acidophilic no surrounding perichondrium

  •Resist deformation under stress
• BONE

  •a specialized connective tissue composed of calcified extracellular material, the bone matrix, and three major cell types.

  • main constituent of the adult skeleton

  •provides solid support for the body

  •protects vital organs

  •harbors cavities containing bone marrow where blood reservoir of calcium, phosphate, and other ions

  •bodily movements

  •Bone tissue is classified as either compact (dense) or spongy (cancellous)
• Compact bone

  • A compact, dense layer forming the outside of the bone.
• Spongy bone

  • a spongelike meshwork consisting of trabeculae (thin, anastomosing spicules of bone tissue) forming the interior of the bone
• perforating (or Sharpey) fibers

  • Bundles of periosteal collagen fibers that penetrate the bone matrix,
• Lacunae

  • Spaces within the bone matrix, each of which contains a bone cell
• Canaliculi

  • small channels that interconnects the lacunae
  • small tunnels into which the osteocyte extends numerous processes
• OSTEON

  • Haversian system

  •refers to the complex of concentric lamellae surrounding a small central canal that contains blood vessels, nerves, loose connective tissue, and endosteum

  •cement line

  •Perforating canals (Volkmann's canals)
• cement line

  • outer boundary of each osteon that is collagen-rich

  layer
• Perforating canals (Volkmann's canals)

  • channels in lamellar bone through which blood vessels and nerves travel from the periosteal and endosteal surfaces to reach the osteonal canal
  • they also connect osteonal canals to one another
• OSTEOBLASTS

  • the differentiated bone-forming cell that secretes bone matrix.

  • Located exclusively at the surfaces of bone matrix
• OSTEOCYTES

  •the mature bone cell enclosed by bone matrix that it previously secreted as an osteoblast. •enclosed singly within the lacunae 

  •flat, almond-shaped osteocytes exhibit significantly less RER, smaller Golgi complexes, and more condensed nuclear chromatin

  •maintain the bony matrix
• OSTEOCLASTS

  • responsible for bone resorption.

  •very large, motile cells with multiple nuclei

  •play a major role in matrix resorption during bone growth and remodeling

  •In areas of bone undergoing resorption, osteoclasts lie within enzymatically etched depressions or cavities in the matrix known as resorption cavities (also called

  Howship lacunae).
• BONE FORMATION

  • The development of a bone is traditionally classified as endochondral or intramembranous.

  •With the primary and secondary ossification centers, two regions of cartilage remain:

  • The layer of articular cartilage within joints which usually persists through adult life and does not contribute to bone growth

  •The specially organized epiphyseal cartilage (also called epiphyseal plate or growth plate), which connects each epiphysis to the diaphysis
• Intramembranous ossification

  • In which osteoblasts differentiate directly from mesenchyme and begin secreting osteoid
• Endochondral ossification

  • in which a preexisting matrix of hyaline cartilage is eroded and invaded by osteoblasts, which then begin osteoid production.
• resting zone

  • consists of hyaline cartilage with typical chondrocytes.
• proliferative zone

  • chondrocytes begin to divide rapidly and form columns of stacked cells parallel to the long axis of the bone.