Tissues

Tissues Groups of cells that have specialized structural and functional roles Four major types Epithelial Connective Muscle Nervous

Epithelial Covers organs Forms the inner lining of body cavities Lines hollow organs Always has a free surface, one that is exposed to the outside or to an open space internally Basement Membrane: nonliving layer of connective tissue that anchors the tissue

Epithelial Tissue Lack blood vessels Cell readily divide Nutrients diffuse from underlying connective tissues Cell readily divide Injuries heal rapidly Skin cells, stomach and intestine lining are continually damaged and replaced Tightly Packed with little intercellular material Effective barriers: skin and mouth Secretion, absorption, excretion, and sensory reception

Simple Epithelium Simple Squamous Epithelium Single thin layer of flattened cells Nuclei are broad and thin Common site of diffusion and filtration Line air sacs, capillaries, blood and lymph vessels Easily damaged

Simple Epithelium Simple Cuboidal Epithelium Single layer of cubed shaped cells Centrally located spherical nuclei Cover the ovaries and lines most kidney tubules Kidney functions in secretion and absorption Glands of certain ducts: thyroid, pancreas, and liver Secretes glandular products

Simple Epithelium Simple Columnar Epithelium Elongated Think tissue  protects underlying tissue Single layer of cells Nuclei located near the basement membrane Line the uterus and most digestive organs Stomach and small intestines Secrete digestive fluids and absorb nutrients Microvilli: cylindrical projections from cell membrane Increase surface area  for increased absorption

Simple Columnar Epithelium

Pseudostratified Columnar Epithelium Appear stratified or layered, but are not Possess cilia, which move constantly Goblet cells scattered throughout secrete mucus Cilia sweeps away Line passage of respiratory system Mucus cover linings trap dust and microorganisms Cilia move the mucus and its captured particles upward and out

Stratified Squamous Epithelium Layered cells  thick tissue Cells divide in deep layers and newer cells push older one outward, where they flatten Outer skin layer, epidermis As they age, accumulate the protein keratin, then harden and die tough, hard, waterproof covering Blocks foreign invaders Line the mouth, throat, vagina, and anal canal Not keratinized

Stratified Squamous Epithelium

Stratified Cuboidal Epithelium Two to three layers of cuboidal cells that form lining of lumen More protection than single layer Lines the larger ducts of mammary glands, sweat glands, salivary glands, and pancreas Lining of developing ovary follicles and seminiferous tubules female and male respectively

Stratified Columnar Epithelium Several layers of cells Superficial cells are elongated Basal layer are cubed shaped Male urethra Parts of the pharynx

Transitional Epithelium Specialized to change in response to tension Inner lining of urinary bladder Lines the ureters and part of the urethra Provides an expandable lining

Glandular Epithelium Specialized to produce and secrete substances into ducts or into body fluids Found in glands Exocrine glands: glands that secrete their products into ducts that open onto some internal or external surface Merocrine Glands: watery, protein rich fluid Apocrine Glands: lose small portions of their glandular cell bodies during secretion Holocrine Glands: the entire cell lyses during secretion Endocrine: secrete products into tissue fluid or blood

Glandular Epithelium

Types of Tissue

Connective Tissue

Functions of Connective Tissue Binds structures Provides support and protection Serves as a framework Fills spaces Store fat Produce blood cells Protect against infection Help repair tissue damage

General Characteristics Farther apart than epithelial Have an abundance of intercellular material between them, matrix Fibers and ground substance Can usually divide Varying degrees of vascularity Especially bone and cartilage Some are flexible Adipose

Major Cell Types Fixed: present in stable numbers Fibroblasts: most common type Large star shaped Produce fibers by secreting proteins into the matrix Mast cells: large widely distributed Near blood vessels Release heparin, prevent blood clotting Release histamine: promotes some reaction of inflammation and allergies

Major Cell Types Wandering: temporarily appear in tissue Macrophages: originate as white blood cells Specialized for phagocytosis Function as scavengers and defensive cells that clears tissues of foreign particles

Connective Tissue Fibers Produced by fibroblasts Collagenous Fibers: thick threads of protein collagen Grouped in long, parallel bundles Slightly elastic and flexible Great tensile strength Components of: Ligaments: bone to bone Tendons: muscle to bone White Fibers

Connective Tissue Fibers Elastic Fibers: elastin protein Branch, forming complex networks Weaker than collagenous fibers Stretch easier and resume original shape Common In: Vocal Cords Yellow Fibers Reticular Fibers Very thin collagenous fibers Highly branched and form delicate supporting networks

Loose Connective Tissue Areolar Tissues: forms delicate, thin membranes Cells located some distance apart and separated by a gel-like matrix containing collagenous and elastic fibers Binds the skin to the underlying organs and fills space between muscles Beneath most epithelium

Adipose Tissue Fat Cushions joints and some organs Insulates for heat Specialized form of connective tissue that develops when certain cells store fat in droplets within the cytoplasm and enlarge Cushions joints and some organs Insulates for heat Stores energy beneath the skin between muscles around kidneys behind eyeballs abdominal membrane surface of the heart around certain joints

Adipose Tissue

Dense Connective Tissue Many closely packed, thick, collagenous fibers Fine network of elastic fibers Relatively few cells, mostly fibroblasts Very strong Poor blood supply  slow repair Part of tendons and ligaments Protective white layer of eyeball Deeper skin layers

Cartilage Chondrocytes: cartilage cells Perichondrium: protective tissue enclosing cartilaginous structures Supplies nutrients Lack of direct blood supply  slow healing Rigid connective tissue Support, framework and attachments Protects underlying tissues Structural models for developing bones

Types of Cartilage Hyaline Cartilage: most common Very fine collagenous fibers in a matrix White glass Ends of bones in joints, soft part of nose, supporting rings of respiratory passage

Types of Cartilage Elastic Cartilage: dense network of elastic fibers More elastic and flexible Ears & larynx Fibrocartilage very tough tissue, many collagenous fibers Shock absorber: knees and pelvic girdle Pads of intervertebral disks between vertebrae

Bone Most rigid connective tissue Hardness: mineral salts between cells calcium phosphate and calcium carbonate Great amount of collagen Supports body structures Protects cranial and thoracic cavities Attachment for muscle Contain red marrow forms WBC Stores and releases inorganic chemicals, Ca and P

More about Bones Osteocytes: bone cells Located in the lacuanae Forms concentric circles Osteon: layers of osteocytes around the osteonic canal Contains blood vessels Material can move rapidly between blood vessels and bone cells Heals faster than cartilage

Blood Transports materials between interior body cells and the external environment Helps maintain homeostasis Composed of formed elements suspended in a fluid matrix Fluid Matrix: blood plasma Formed Elements: RBC, WBC, platelets Forms in red marrow in long bones

Muscle and Nervous Tissues

Muscle Tissue Contractile Muscle Fibers: elongated cells that can shorten Move body parts As they contract, fibers pull at their attached ends 3 Types Skeletal Muscle Tissue Smooth Muscle Tissue Cardiac Muscle Tissue

Skeletal Muscle Tissue Muscle is attached to bone Voluntary: consciously controlled Contract when stimulated by nervous impulse then relax Moves head, trunk, and limbs Facial Expressions, write, talk, sing, chew, swallow, and breathe

Skeletal Muscle Tissue Appearance Long thread like fibers Striations: alternating light and dark cross-markings Each cell has many nuclei just beneath the cell membrane

Smooth Muscle Tissue Smooth  cells lack striations Shorter than skeletal cells Spindle-shaped Single, centrally located nucleus Comprises the walls of hollow internal organs Stomach, intestines, urinary bladder, uterus, and blood vessels

Smooth Muscle Tissue Involuntary: cannot be consciously stimulated Moves food through digestive tract Constricts blood vessels Empties urinary bladder

Cardiac Muscle Tissue Only in the heart Bulk of the heart Pumps blood through the heart chambers into blood vessels Cells: striated and joined end to end Muscle fibers are branched Connected in complex networks Single nuclei Intercalated disk: where it touches another cell Specialized intercellular junction Controlled involuntarily

Cardiac Muscle Tissue

Nervous Tissue Brain, spinal cord, and peripheral nerves Neurons: basic cells Send nerve impulses along cytoplasmic extensions, or nerve fibers Single to: neutrons, muscles, or glands Coordinated, regulate, and integrate many body functions

Nervous Tissue Neuroglial Cells Support and bind the components of nervous tissue Carry on phagocytosis Supply nutrients to neurons  connecting with blood vessels

Neuroglial Cells