The Tissue Level of Organization Chapter 4 The Tissue Level of Organization

Tissues: The “Real” A&P

Histology: The Study of Tissues

Tissues and Histology Tissue Level of Organization Epithelial Connective Muscle Nervous Histology: Microscopic Study of Tissues

Embryonic Tissue Germ layers Endoderm Mesoderm Ectoderm Inner layer Forms lining of digestive tract and derivatives Mesoderm Middle layer Forms tissues as muscle, bone, blood vessels Ectoderm Outer layer Forms skin and neuroectoderm

Epithelium Characteristics Consists almost entirely of cells Covers body surfaces and forms glands Has free and basal surface Specialized cell contacts Avascular Undergoes mitosis

Functions of Epithelia Protecting underlying structures Acting as barriers Permitting the passage of substances Secreting substances Absorbing substances

Classification of Epithelium Simple Squamous, cuboidal, columnar Stratified Pseudostratified columnar Transitional Cuboidal to columnar when not stretched and squamouslike when stretched

Types of Epithelium

Types of Epithelium

Types of Epithelium

Types of Epithelium

Types of Epithelium

Types of Epithelium

Types of Epithelium

Types of Epithelium

Functional Characteristics Cell layers and shapes Diffusion, Filtration, Secretion, Absorption, Protection Cell surfaces Microvilli: Increase surface area absorption or secretion Cilia: Move materials across cell surface Cell connections Desmosomes, tight, gap Glands Exocrine: Have ducts Endocrine: Have no ducts

Cell Connections Functions Types Bind cells together Form permeability layer Intercellular communication Types Desmosomes Tight Gap

Exocrine Glands Unicellular Goblet cells

Multicellular Exocrine Glands

Exocrine Glands and Secretion Types Merocrine Sweat glands Apocrine Mammary glands Holocrine Sebaceous glands

Connective Tissue Abundant Consists of cell separated by extracellular matrix Diverse Performs variety of important functions

Functions of Connective Tissue Enclosing and separating as capsules around organs Connecting tissues to one another as tendons and ligaments Supporting and moving as bones Storing as fat Cushioning and insulating as fat Transporting as blood Protecting as cells of the immune system

Connective Tissue Cells Specialized cells produce the extracellular matrix Suffixes -blasts: create the matrix -cytes: maintain the matrix -clasts: break the matrix down for remodeling Adipose or fat cells Mast cells that contain heparin and histamine White blood cells that respond to injury or infection Macrophages that phagocytize or provide protection Stem cells

Extracellular Matrix Components Protein fibers Ground substance Fluid Collagen which is most common protein in body Reticular fill spaces between tissues and organs Elastic returns to its original shape after distension or compression Ground substance Shapeless background Fluid

Connective Tissue Categories Embryonic or mesenchyme Adult Loose Dense Connective tissue with special properties Cartilage Bone Blood

Loose Connective Tissue Also known as areolar tissue Loose packing material of most organs and tissues Attaches skin to underlying tissues Contains collagen, reticular, elastic fibers and variety of cells

Dense Connective Tissue Dense regular Has abundant collagen fibers Tendons: Connect muscles to bones Ligaments: Connect bones to bones Dense regular elastic Ligaments in vocal folds Dense irregular Scars Dense irregular collagenous Forms most of skin dermis Dense irregular elastic In walls of elastic arteries

Dense Regular Connective Tissue

Dense Irregular Connective Tissue

Connective Tissue with Special Properties Adipose tissue Consists of adipocytes Types Yellow (white) most abundant, white at birth and yellows with age Brown found only in specific areas of body as axillae, neck and near kidneys Reticular tissue Forms framework of lymphatic tissue Characterized by network of fibers and cells

Adipose Tissue

Reticular Tissue

Cartilage Composed of chondrocytes located in spaces called lacunae Next to bone firmest structure in body Types of cartilage Hyaline Fibrocartilage Elastic

Hyaline Cartilage Found in areas for strong support and some flexibility Rib cage and cartilage in trachea and bronchi Forms most of skeleton before replaced by bone in embryo Involved in growth that increases bone length

Fibrocartilage Slightly compressible and very tough Found in areas of body where a great deal of pressure is applied to joints Knee, jaw, between vertebrae

Elastic Cartilage Rigid but elastic properties External ears, epiglottis

Bone Hard connective tissue that consists of living cells and mineralized matrix Organic and inorganic Types Cancellous or spongy bone Compact bone

Bone

Blood Matrix between the cells is liquid Hemopoietic tissue Forms blood cells Found in bone marrow Yellow Red

Bone Marrow

Muscle Tissue Characteristics Types Contracts or shortens with force Moves entire body and pumps blood Types Skeletal Striated and voluntary Cardiac Striated and involuntary Smooth Nonstriated and involuntary

Skeletal Muscle

Cardiac Muscle

Smooth Muscle

Nervous Tissue Found in brain, spinal cord and nerves Ability to produce action potentials Cells Nerve cells or neurons Consist of dendrites, cell body, axons Consist of multipolar, bipolar, unipolar Neuroglia or support cells

Neurons

Neuroglia

Membranes Mucous Serous Synovial Line cavities that open to the outside of body Secrete mucus Serous Line cavities not open to exterior Pericardial, pleural, peritoneal Synovial Line freely movable joints Produce fluid rich in hyaluronic acid

Inflammation Response when tissues damaged or with an immune response Manifestations Redness, heat, swelling, pain, disturbance of function Mediators Include histamine, kinins, prostaglandins, leukotrienes Stimulate pain receptor and increase blood vessel permeability

Tissue Repair Substitution of viable cells for dead cells Skin repair Primary union: Edges of wound close together Wound fills with blood Clot forms Scab Pus Granulation tissue Scar Secondary union: Edges of wound not close Clot may not close gap Inflammatory response greater Wound contraction occurs leading to greater scarring

Tissue Repair

Tissues and Aging Cells divide more slowly in older than younger people Tendons and ligaments become less flexible and more fragile Arterial walls become less elastic Rate of blood cell synthesis declines in elderly Injuries are harder to heal in elderly