Chapter 5 Tissues – Epithelial, Connective, Muscle, Nervous, Membranes (Continued)

HISTOLOGY, Continued Chapter 5 Connective tissue, nervous tissue,& muscle tissue Connective Tissue • Most abundant, widely distributed, and histologically variable type of tissue • Cells occupy less space than matrix • Most cells are not in direct contact with each other • Highly variable vascularity • Loose connective tissues have many blood vessels • Cartilage has no blood vessels Connective Tissue • Main types 1.Fibrous 2.Adipose 3.Supportive 4.Fluid Connective Tissue • Most abundant, widely distributed, and histologically variable type of tissue Functions of Connective Tissue • Bind organs to each other (e.g., fat holds kidneys) • Support (e.g., cartilage supporting ears) • Protection (Structural and immunological) • Movement (e.g., bones lever system) • Storage (e.g., fat for energy, calcium in bone) • Heat production (metabolism of brown fat) • Transport or substances (nutrients, waste, hormones, blood cells) Fibrous Connective Tissue Cell types: • Fibroblast: produce fibers and matrix gel (ground substance) • Leukocytes (WBCs): attack and react against bacteria • Macrophages: phagocytize foreign material, activate immune system • Plasma (B) cells: make antibodies • Mast cells: secrete heparin (inhibit clotting) and histamine (allergic reaction, vasodilation) Fibrous Connective Tissue • Fiber types • Collagenous (white fibers) • Tough, resist stretching • E.g., found in tendons, ligaments, dermis • Reticular • Thin, sponge-like, coated with glycoprotein • Framework for some organs (e.g., spleen, lymph nodes) • Part of basement membrane (epithelial) • Elastic • Elastin and fibrillin • Ability for tissues/organs to spring back after stretched Fibrous Connective Tissue • Loose connective tissue • Large space between cells 1. Areolar • Loosely organized fibers • Beneath epithelial layers • Contains blood vessels 2. Reticular • Reticular fibers and fibroblasts • Blood between fibers (like bloody sponge) Fibrous Connective Tissue • Dense connective tissue • Fibers occupy more space than cells & matrix • Tightly packed 1. Dense regular • Collagen fibers + fibroblasts • Collagen fibers tightly packed • Fibers parallel (predictable muscle movement/stress) 2. Dense irregular • Collagen fibers – random directions Adipose Tissue • Adipocytes • Store fat (energy reservoir) • Not stagnant  constant turnover (equilibrium) • 2 types of fat 1. White fat • Most abundant • Insulation, cushions organs 2. Brown fat • Fetuses, infants, children • Shoulders, upper back • Enzymes and blood vessels • Generates heat  Release ALL energy as heat Diagram: white fat Cartilage • Firm CT, flexible matrix • Shape and support • Chondroblasts • Produce cartilage • Secrete matrix until surrounded  Become chondrocytes • Avascular Cartilage • 3 Types 1. Hyaline • Fineness of collagen fibers  Clear, glassy • Eases joint movement, holds airway open, moves vocal cords, growth of juvenile long bones 2. Elastic 3. Fibrocartilage Hyaline cartilage Cartilage • 3 Types 1. Hyaline 2. Elastic • Contain elastic fibers • Provides flexible, elastic support • Locations: external ear and epiglottis 3. Fibrocartilage Hyaline cartilage Elastic cartilage Cartilage • 3 Types 1. Hyaline 2. Elastic 3. Fibrocartilage • Large, course bundles of collagen • Resists compression and absorbs shock • Locations: pubic symphysis, menisci, and intervertebral discs Hyaline cartilage Elastic cartilage Fibrocartilage Bone • Calcified 1. Spongy • Heads of long bones • Middle of flat bones 2. Compact • Dense, no visible spaces • External surfaces (covers spongy bone when present) Blood • Transport cells and matter • Fluid CT • More ground substance/matrix than cells  blood plasma • Produced by tissues of bone marrow • Formed elements • Cell components of blood plasma 1. Erythrocytes (RBCs) 2. Leukocytes (WBCs) Nervous Tissue • Communication • Electrical signaling • Chemical signaling • Neurons • Detect stimuli • Transmit information • Neuroglial cells • Support cells for neurons • “housekeepers” of nervous system Neuroglial Cells • Microglia • Immune response • Hyperactive in Alzheimer’s disease • Astrocytes • Maintain environment • Oligodendrocytes • Axon support – myelin sheaths (CNS) • Schwann cells • Myelinate axons (PNS) • Ependymal cells • Central Nervous System Peripheral Nervous System Muscle Tissue • Muscle Fiber = cell (in muscle) • Contract when stimulated • Exert force on tissues, organs, fluids • Movement • Digestion • Breathing • Circulation 1. Skeletal 2. Smooth Skeletal Muscle • Made of muscle fibers—long thin cells • Most skeletal muscles attach to bone • Contains multiple nuclei adjacent to plasma membrane • Striations—alternating dark and light bands • Voluntary—conscious control over skeletal muscles Cardiac Muscle • Limited to the heart wall • Cardiomyocytes are short and branched with one centrally located nucleus; muscle, short, cells of the heart • Intercalated discs join cardiomyocytes end to end • Gap junctions • Striated and involuntary (not under conscious control) Smooth Muscle • Made of short, fusiformshaped cells • Cells have one central nucleus, no striations • Involuntary function • Gap junctions • Most is visceral muscle— making up parts of walls of hollow organs Membranes • Faces the outside environment & line cavities and organs & • Cutaneous membrane: skin • Internal membranes 1. Mucous membrane • Line passage to external environment • Epithelium, areolar CT, smooth muscle Next: Integumentary System & Bones