Connective Tissue

Connective Tissue

1. Connective Tissue Proper

   • Dense CT
     • Dense Regular CT
       • "White CT"
       • Collagenous fibers traveling in parallel
       • Tendons, ligaments, aponeuroses, perichondrium/periosteum
       • Provides tinsel strength
     • Dense Irregular CT
       • "White CT"
       • Collagenous fibers
       • Dermis, sclera, submucosa, fibrous capsules, perichondrium/periosteum
       • Provides resistance to forces in different directions
     • Elastic CT
       • "Yellow CT"
       • Elastic Fibers
       • Aorta and other blood vessels, ligamentum flavum, lungs, vocal chords, suspensory ligaments of the penis
       • Provides elasticity while binding structures
       • NOT ELASTIC CARTILAGE
   • Loose CT
     • Reticular CT
       • Reticular fibers
       • Supporting storm in spleen + lymph organs
       • Creates a structural framework for cell attachment and mobility
     • Areolar CT
       • "Loose CT"
       • Elastic fibers, collagenous fibers, reticular fibers, fibroblasts
       • Widely distributed; underlying epithelial tissue
       • General binding of tissues
     • Adipose CT
       • White Fat
         • Hypodermis, viceral fatty tissues (fats around organs i.e. perinephric fats)
         • Storage of potential energy, insulation, protection
         • Adipocytes
       • Brown Fat
         • Adipocytes (with more mitochondria)
         • Back and shoulders of neonates (persists, to a degree, in adults)
         • Thermoregulation in neonates
     • Embryonic CT
       • Mesenchyme
         • pleuripotent cells with stellate appearances, reticular fibers along cytoplasmic extensions
         • CTs of the embryo
         • Gives rise to adult CTs
       • Mucoid CT
         • "Whatron's Jelly"
         • Similar to mesenchymal CT but more extracellular space and less reticular fibers/fibroblasts
         • Umbilical cord, embryonic subcutaneous tissue
         • Gives rise to adult tissues

2. Specialized Connective Tissue

   • Cartilage
     • Hyaline Cartilage
       • Gristle
       • Chondrocytes, isogenous groups (pairs, out on dates), homogeneous matrix appearance
       • Costal cartilage, fetal skeleton, nasal septum, thyroid/cricoid/tracheal rings, epiphyseal plates
         • Costal cartilage = common site for cartilage grafting
       • Endochondral ossification, ventilation, firm with minimum flexibility
     • Fibrocartilage
       • Chondrocytes, collagen oriented in parallel
       • symphysis joints (intervertebral discs, pubic symphysis, etc.), menisci
       • Provides cushion and resistance to torque
     • Elastic Cartilage
       • Chondrocytes, elastic fibers
       • Pinna of the ear, epiglottis
       • Provides flexibility with minimal strength
   • Osseous tissue
     • aka bone / bone tissue
     • Osteon with lacunae and canaliculi, collagen matrix (decalcified)
       • lacunae = little lakes
       • canaliculi = little canals
     • Seen in bones
     • Structure, site of hematopoiesis
     • Has mineral matrix
   • Blood
     • Erythrocytes
     • Leukocytes
       • Granulocytes
         • Neurophils
         • Basophils
         • Eosinophils
         • "Phil loves his granny"
       • Agranulocytes
         • Lymphocytes
         • Monocytes
     • Plasma (fluid matrix)
     • Platelets (thrombocytes)
     • Within bloodvessels/heart
     • Transport of nutrients, gasses, immune functions, etc

3. Extracellular matrix

   • Fibers
     • Collagenous (Collagen) fibers
       • Flexible with great tensile strength
       • Collagen molecule = tropocollagen (3 polypeptide chains [alpha helices])
       • Type I collagen = 90% of body collagen (dermis, bones, tendons)
       • Type II = cartilage
       • Type IV = basal lamina of basement membrane
     • Reticular fibers
       • Type III collagen, arranged in mesh like pattern
       • Produced by fibroblasts, reticular cells, Schwann cells, smooth muscles cells
       • i.e. Lymph nodes, spleen... Tree, wind, owls metaphor
     • Elastic fibers
       • Thinner than collagen fibers
       • Elastin
         • Similar to collagen but configuration constantly changes, can be uncoiled with force and naturally recoils
       • Microfibrils
         • Fibrillar glycoproteins, serves as scaffold for elastin
   • Ground substance
     • H2O
     • Proteoglycan
       • Core protein
       • Glycosaminoglycans (GAGs)
         • Chondroitin sulfate
         • Keratan Sulfate
         • Glucosamine
     • Hyaluronic acid
       • Bind to form macromolecules called proteoglycan aggregates
       • a GAG but much larger than other ones