Connective Tissue

1. Connective Tissue

2. Connective Tissue • Support and attachment for various organs, fills body spaces giving body form and maintenance • Composed of 3 main elements – cells, fibers and ground substance (fiber and ground substance = extracellular matrix or ECM) • Derived from the embryonic tissue, mesenchyme

3. Classification • Classified based on the nature of the matrix • Ground substance – amorphous (unstructured) material that fills the space between cells • Fibers – 3 types • Cells – 2 types

4. 3 Types of Fibers • Collagen fibers (white fivers in fresh tissue, pink on slide) – strong, non-elastic with great tensile strength and flexibility • Elastic fibers (yellow fibers, dark purple on slide) – thinner, not as strong as collagen fibers, randomly coiled, wavy look • Reticular fibers (dark purple on slide) – very thin, fine fibers that branch extensively and form a network

6. Reticular Collagen Fibroblasts Elastic

7. Cell Types • Cells – 2 types • –blast cells – immature, actively mitotic cells, used to build matrix • –cyte cells – mature, non-mitotic cells, maintain matrix CT-Proper Fibroblast Fibrocyte Cartilage Chondroblast Chondrocyte Bone Osteoblast Osteocyte Blood Hemocytoblast Various types (erythrocyte, thrombocyte, leukocyte)

8. Classification of Connective Tissue Subtypes • Mesenchyme (Common embryonic tissue) • Connective tissue Proper Loose – • 3 specific types: Areolar, Adipose, Reticular • Connective tissueProper Dense – • 3 specific types: Regular Dense, Irregular Dense, Elastic • Cartilage – • 3 specific types: Hyaline Cartilage, Fibrocartilage, Elastic Cartilage • Osseous (Bone) – • 2 specific types: Compact Bone, Spongy (cancellous) Bone • Blood – • Cell types: Erythrocytes (red blood cells), Leukocytes (white blood cells), Thrombocytes (platelets)

9. Subtype: Mesenchyme • Forms the undifferentiated “filling” of the early embryo • Forms CT between and within developing tissues and organs • In adults, only found in dental pulp • Consists of mesenchymal cells with stem cell properties (able to give rise to other cells)

12. Subtype: Loose CT Proper, Specific Type: Areolar • Loosely organized matrix with all 3 fiber types • Fibrocytes most common cells (flat or spindle shaped), although mast cells and macrophages (immune cells) present • Ground substance – semifluid • Functions: widespread flexible framework within and between organs. Contain blood vessels that nourish surrounding tissue and is site of immune reactions • Location: beneath epithelial tissues, around and within muscles and nerves and in come serous membranes, composes superficial fascia

15. Subtype: Loose CT Proper, Specific Type: Adipose • Cytoplasm and nucleus compressed to edge of cell by large lipid droplet • Adipocytes (“signet cells”) filled with fat • Ground substance - very little • Fibers – none • Function: protective cushion and insulation throughout body • Location: buttocks, breasts, surrounding kidneys, eye sockets

17. Subtype: Loose CT Proper, Specific Type: Reticular • Network of fine (reticular) fibers • Ground substance – semifluid • Cells - reticular cell (type of fibroblast that produces reticular fibers) • Function: provides supporting framework for many vascular organs, hematopoietic tissue and lymph nodes • Location: spleen, bone marrow, lymph nodes

20. Subtype: Dense CT Proper, Specific Type: Regular • Closely packed collagen fiber bundles in parallel arrangement • Ground substance - very little • Fibers - mostly parallel collagen fibers • Cells – Fibrocyte • Function: tensile strength • Location: Tendons, aponeurosis, ligaments. Forms the deep fascia

23. Subtype: Dense CT Proper, Specific Type: Irregular • Bundles of collagen fibers (and a few elastic fibers) randomly interwoven • Ground substance - very little • Cells – fibrocyte • Function – strength from many directions • Locations: most of skin dermis, sheaths around nerves and tendons

26. Subtype: Dense CT Proper, Specific Type: Elastic • Bundles of parallel elastic fibers that branch and unite with one another • Ground substance - very little • Fibers – elastic • Cells – fibrocyte • Function – great elasticity (flexibility) • Location: ligaments of vertebral column and walls of large arteries

29. Subtype: Cartilage • Surrounded by a fibrous membrane called the perichondrium • Mature cells, called chondrocytes, lie in lacunae • Lack blood vessels • Cells derive nourishment by diffusion from capillaries in the perichondrium

30. Subtype: Cartilage, Specific Type: Hyaline • Matrix - firm with an imperceptible fibers (collagen) (i.e. fibers not routinely visible) • Most common type of cartilage • Cells - chondrocyte in lacunae (mature) • Function: provides smooth surface so tissues may move easily over one another. Also provides flexibility and support • Location: composes much of fetal skeleton prior to ossification, covers ends of long bones in adults, cartilaginous part of nasal septum, trachea and costal cartilage

32. Subtype: Cartilage, Specific Type: Fibrocartilage • Alternating bundles of collagen fibers and rows of chondrocytes, lack perichondrium • Matrix - semi-firm thick collagen fibers • Cells - chondrocyte in lacunae • Function: provide support and rigidity to surrounding structures, strongest of the 3 types of cartilage • Location: intervertebral discs, pubic symphysis, meniscus of knee joint

35. Subtype: Cartilage, Specific Type: Elastic • More flexible and elastic than hyaline cartilage • Matrix - firm with obvious elastic fibers • Cells - chondrocyte in lacunae • Function: provide support to surrounding structures and to define and shape area in which it is present • Location: external ear (auricle), auditory tubes, epiglottis

38. Subtype: Osseous (Bone) • Hard, strong and lightweight • Bone is continually modified and reconstructed (remodeling)

39. Subtype: Osseous (Bone), Specific Type: Compact • Compact bone (Ground Bone and decalcified bone slides) • Composed of functional units called osteons (concentric circles with central canal) • Matrix - hard and calcified with many collagen fibers • Cells - osteocytes in lacunae within matrix • Function: protection, support, and storage of minerals • Location: skeleton

42. Subtype: Osseous (Bone), Specific Type: Spongy • Spongy (Cancellous) bone • Interior to and continuous with compact bone • Numerous trabeculae (branching bony plates) with interconnecting spaces. The space are filled with marrow • Matrix - hard and calcified with many collagen fibers but lacks bone lamellas. • Cells - osteocytes in lacunae within matrix • Function – protection, support, storage of bone marrow

44. Subtype: Blood • Make up of formed element (blood cells) and plasma (fluid) • Matrix - plasma- fluid • Cells - Blood cells –erythrocytes (red blood cells), leukocytes (white blood cells), thrombocytes (platelets, cell fragments) • Fibers are only present during clotting • Function: transport of oxygen, waste, nutrients and hormones, aids in regulation of body temp, maintains homeostasis by buffering tissue

46. Nervous Tissue

47. Nervous System • Transmit information • Cells • Neurons - nerve cell bodies (soma) with dendrite and axon processes, major cell type • Supporting cells - non-conducting support cells