Connective Tissue Lecture

Question 1

Connective Tissue (Def. , 2 Big Details)

Answer 1

A. Characterized by the presence of several types of cells immersed in abundant intercellular material synthesized by these cells.
B. intercellular material contains:
1. water (tissue fluid)
2. fibers - with definite structure
3. matrix - an amorphous intercellular substances composed of acid mucopolysaccharides and glycoproteins.
C. All C.T. embryologically develops from mesenchyme - embryonic tissue characterized by cells embedded in abundant amorphous intercellular substance - derives from embryo middle layer - mesoderm.

Question 2

Functions of Connective Tissue (8-9 Details)

Answer 2

A. form capsules surrounding organs
B. forms internal supportive architecture of organs
C. tendons
D. ligaments
E. areolar tissue - tissue that fills the space between organs
F. Bone and cartilage
G. functions in nutrition by close association with blood vessels and as blood itself
H. functions in defense: contains phagocytic and antibody-producing cells

Question 3

Intercellular Material: Fibers (Collagenous Fibers)

Answer 3

• these fibers are colorless, but they cause material in which they are present in great numbers to be white (e.g. tendons and aponeurosis
• collagenous fibers are acidophilic, therefore they stain pink with most histological stains.
• Composed mainly of the protein collagen (in the form of tropocollagen)–most abundant protein of the human body
• represents about 30% of the total body proteins.
• many times collagen fibers are arranged in parallel as bundles.
• each fiber is composed of many parallel fibrils.
• each fibril is composed of even finer filaments called microfibrils (cannot be seen with light microscope).

Question 4

Intercellular Material: Fibers (Elastic Fibers)

Answer 4

• thinner than collagenous fibers
• when present in great quantities–they appear characteristically yellow.
• These fibers yield to small traction forces and then return to their original shape when these forces are relaxed. Can be stretched up to 1/2 their length.
• stain weakly and irregularly with most stains
• principle component – elastin: a protein produced by fibroblasts in skin, and by small muscle cells in walls of large vessels.

Question 5

Intercellular Material: Fibers (Reticular Fibers)

Answer 5

• fine fibers about the same diameter as collagen.
• not visible with normal staining (e.g. H&E)
• appear black with silver impregnation techniques.
• often continuous with collagenous fibers (which appear brown with Ag impregnation).
• like collagenous fibers - composed mainly of protein collagen.
• found as a framework in some organs (e.g. Hematopoietic organs like spleen, lymph nodes and red bone marrow)

Question 6

Intercellular Material: (Amorphous Intercellular Substance)

Answer 6

• colorless, transparent, and homogenous.
• fills space between cells and fibers of connective tissue.
• chemical nature is not completely understood but is composed mainly of acid mucopolysaccharides and glycoproteins (protein and carbohydrate complexes) - hyaluronic acid.
• substance is produced by fibroblasts.
• acid mucopolysaccharides influence the amount of water in connective tissue - they are very hydrophilic and most water present in intercellular substance is associated with these molecules - impossible say to draw water out with hypodermic syringe - but still allows diffusion of substances

Question 7

Cells (Fibroblasts)

Answer 7

• most common cell type in C.T.
• these cells produce collagen and acid mucopolysaccharides
• responsible for synthesizing intercellular material of C.T.
• in “resting state” these are sometimes referred to as “fibrocytes”. However, if C.T. repair is necessary, then never go back to their original synthesized form.

Question 8

Cells (Macrophages)

Answer 8

• distinguished by this great capacity for pinocytosis and phagocytosis rather than by its morphologic characteristics which tend to very greatly.
• may be either fixed or wandering – these represent different phases of the same cell, and one may transform itself into the other.
• sometimes called “histocytes” in older literature.
• main function is in defense of the organism.
• if they encounter very large foreign particles, they have the ability to fuse with one another forming very large multinucleated cells (100 or more nuclei) called foreign body giant cells.

Question 9

Cells (Adventitial cells – Cells of Regeneration)

Answer 9

-cells that maintain their embryonic mesenchymal potential to give rise to any kind of C.T. cells (also smooth muscle cells) (e.g. important in formation of new or regeneration of damaged C.T. or blood vessels)

Question 10

Cells (White Blood Cells (Leukocytes) (Def. and 2 details)

Answer 10

– white blood cells freely leave the circulation and migrate through connective tissues:

1. Mast Cells – contain histamine and heparin
   - heparin – anticoagulant for blood.
   - histamine – capillary dialator and increase B.V. permeability.
2. Plasma cells – usually very few in number except in areas of inflammation or subject to penetration of bacteria or foreign proteins.
   - produce antibodies for the body’s defense.

Question 11

Cells (Other Leukocytes (white blood cells) (Def. and 2 big details)

Answer 11

• have ability to migrate back and forth across B.V. walls
• especially present in inflammation.
• Eosinophils, Basophils & Lymphocytes – these cells also function in the immune response.

Question 12

Cells (Adipose Cells)

Answer 12

• signet ring shaped cells specialized for the storage of fat.

Question 13

Connective Tissue Types (List Them) 7

Answer 13

• Connective Tissue Proper
• Elastic Connective Tissue
• Reticular Tissue
• Adipose Tissue
• Cartilage
• Bone
• Blood

Question 14

Connective Tissue Types (Connective Tissue Proper) *2 Components

Answer 14

1. Loose C.T. - also called Areolar - most widely distributed connective tissue type.
   - found most abundantly in subcutaneous or intermuscular tissue.
   - delicate in consistency and flexibility - not resistant to stress.
2. Dense C.T. - composed of same components as loose - but a clear predominance of collagenous fibers.
   - fewer cells than loose C.T.
   - less flexible and more resistant to stress.
   - called irregular when collagen bundles don’t have definite orientation (example: dermis of skin)
   - called regular when collagen bundles arranged in definite pattern.
   - usually formed in response to prolonged stress in same direction. (example: tendon, ligament)

Question 15

Connective Tissue Types (Reticular Tissue)

Answer 15

• composed of reticular fibers and C.T.
• some people believe may have a greater amount of adventitial cells.
• encountered in blood producing organs and stroma (e.g. marrow, thymus, spleen, lymph glands)

Question 16

Connective Tissue Types (Elastic C.T.)

Answer 16

• composed of bundles of elastic fibers.
• surrounded by loose C.T. (example: some ligament of vertebral column)
• has elasticity.

Question 17

Connective Tissue Types (Adipose Tissue) *2 TYPES

Answer 17

• important and energy reservoir.
• forms pads that act as shock absorbers.
• contributes to bodies thermal insulation.
• Unilocular (common yellow) Adipose tissue or Multilocular (brown) Adipose tissue.

1. Unilocular - probably all adipose tissue in adults is of this type.
   - contains only 1 droplet of fat
   - signet ring shape
   - tissue is richly vascularized
   - stored lipids -triglycerides
   - fatty acids are transported to adipocyte - then absorbed and combined to form triglycerides.
2. Multilocular Adipose Tissue (brown)
   - more than one fat droplet
   - more common in hibernating animals
   - produced heat - present to limited extent in newborn but probably does not persist into adulthood.
   - cells are smaller than unilocular

Question 18

Connective Tissue Types (Cartilage) * Types as well

Answer 18

C.T. where intercellular material has a rigid consistency

• functions in support of soft tissues and by virtue of its smooth surface, provides a sliding area for joints.
• made up of intercellular material - cartilage matrix with cavities - lacunae which contain cartilage cells -chondrocytes
• surrounded by perichondrium
• special layer of C.T. which covers cartilage
• intercellular matrix is made up of collagen or collagen plus elastin, associated with acid mucopolysaccharides
• chondrocytes synthesize and maintain matrix
• normally occupy the entire lacunae, but shrink in histologic prep.
• # of fibers varies with weight bearing load
• devoid of blood vessels - nourished solely by diffusion from adjacent C.T. or from synovial fluid in joints
• also no lymphatics or nerves
• 3 types: hyaline, elastic, and fibrous

Question 19

3 types of Cartilage CT

Answer 19

1. Hyaline Cartilage
   - most common form
   - serves as temporary skeleton in embryo - replaced gradually by bone
   - in adults - present mainly in the walls of the respiratory passages (trachea and bronchi), on ventral ends of ribs, and on bone surfaces in joints (articular cartilages)
   - matrix contains collagenous fibers - not easily visible in L.M. - present as fibrils
   - growth of cartilage is due to “interstitial” growth (more in young people) and mitotic division of chondrocytes.
   - In adults mostly from “apposition” - when cells of the perichondrium differentiate into chondrocytes.
   - Regeneration: except in young children, damaged cartilage regenerates with difficulty - often incompletely - when cartilage fractures new cartilage forms from the perichondrium. If extensively damaged - a scar of dense C.T. will form instead of cartilage.
2. Elastic Cartilage - (found in auricle of ear and epiglottis and other places).
   - similar to hyaline cartilage but in addition has an abundant network of fine elastic fibers.
   - frequently found to be gradually continuous with hyaline cartilage.
   - grows mainly by apposition like hyaline
   - less susceptible to degenerative processes than hyaline
3. Fibrocartilage - sort of intermediate between Dense C.T. and Hyaline Cartilage
   - found in intervertebral disks, and public symphysis
   - contains collagen bundles in irregular bundles between bulky groups of chondrocytes
   - develops from dense C.T.
   * Intervertebral Discs - situated between vertebrae and anchored by ligaments
   - composed of Annulus Fibrosus and Nucleus Pulposus - Annulus Fibrosus - mainly composed of fibrocartilage and surrounded by Dense C.T. - Nucleus Pulposus - situated in the center of Annulus Fibrosus - composed of a few round cells in an amorphous semi-fluid substance - gradually reduces in size with age
   - “Slipped Disc” - rupture of Annulus Fibrosus it can then enter the
   vertebral canal compressing the spinal cord.

Question 20

CANCER

Answer 20

A. Not a single disease - but actually many different diseases grouped together under one name.
B. Basically is simply cells dividing and duplicating out of control - can occur in many different tissues of the body.
C. Tumor = growth, or excess cell division resulting in excess of tissue.
D. Oncology - study of tumors.
E. Benign Growth = non-cancerous, non-invasive growth.
F. Malignant Tumor = Malignancy = dangerous, invasive or spreading cancer.
G. Metastasis = spread of cancerous cells to other tissues in other parts of the body. If metastasis progresses beyond a point, the cancer can no longer be treated with surgery.
1. Primary Tumor = the site of original unchecked growth.
2. Secondary Tumor = tumor developing at site of metastasis (few people die of primary tumors)

Question 21

Types of Cancer (3 types w/ subtypes)

Answer 21

• over 100 different types have been identified but identification usually includes norms indicating the tissue origin.
  1. Carcinoma = epithelial cell derived

2. Sarcoma = cancer from a connective tissue (general term)
   a. Osteogenic Sarcoma = cells of bone = most common type of childhood cancer.
   b. Myeloma = cancer in bone marrow - affects the blood.
   c. Chondrosarcoma = cancer in cells of cartilage.
3. Glioma = brain cancer (glial cells of nervous system)
   a. Neuroblastoma = a rare childhood cancer involving nerve cells