Histology
Body Tissues Cells are specialized for particular functions Tissues Groups of cells with similar structure and function Extracellular Matrix cell glue between cells Histology study of tissue
Body Tissues Four primary types (functional categories) Epithelium protection /secretion /absorption/ filtration Connective support & structure Nervous communication & control Muscle movement (internal & external)
Primary Germ Layers Endoderm (Epithelial) Digestive & respiratory epithelium Mesoderm (Epithelial, Muscle, Connective) Muscles Ectoderm (Epithelial, Nervous) Epidermis Urethra epithelium Skeleton (bones & cartilage) Lining of mouth, anus, nostrils Bladder Blood Sweat & sebaceous glands Liver & pancreas Blood vessel epithelium Hair Dermis Excretory & reproductive organs Brain & spinal cord Eyes, nose, ear epithelium
EPITHELIAL TISSUES
Epithelial Functions Protection Sensory Secretion Absorption Excretion
Epithelium Characteristics High cellularity cells fit closely together very little EC matrix Contains specialized contacts tight junctions & desmosomes Avascular no blood vessels within it diffusion provides nutrients & carries waste away lots of nerve fibers Reinforcement & connection Defines boundaries cancer causes a breach in these boundaries Regenerate easily if well nourished Found in areas of high friction
Classification of Epithelium Combination of shape & # of cells is used to name tissues Shape of cells Squamous flattened Cuboidal cube-shaped Columnar column-like
Classification of Epithelium Number of cell layers Simple one layer found in areas of transport Stratified more than one layer High abrasion areas for protection Secretory membranes
Classification of Epithelium Pseudostratified False layers Ciliated (respiratory tract) Non-ciliated (male urethra) Transitional multiple layers of epithelial cells, hodge-podge Found in urinary tract can look cuboidal until bladder stretches, then looks squamos
Keratinized Epithelium Keratin tough waterproof material found in upper layers of some stratified squamos epithelium
Non-Keratinized Epithelium
Epithelial Membranes Mucous membranes Line body cavities OPEN to the exterior Example: digestive, respiratory, urogenital Mucus protects by trapping microorganisms, substances in mucus will destroy them Cutaneous Membranes Skin Helps waterproof & protect body First line of defense in immune system Serous Membranes Lines all CLOSED body cavities Serous fluid located between layers to reduce friction due to organ motion
Epithelial Membranes
Glandular Epithelium Gland one or more cells that secretes a particular product Two major gland types Endocrine gland Ductless secretes product directly into blood or tissue Produces hormones Exocrine gland Empty through ducts to the epithelial surface Include sweat and oil glands
Glandular Epithelium Apocrine secrete their product from intact cells Ex: Mammary glands Holocrine entire cells and their secretions accumulate as the gland s secretory product cells rupture Ex: Sebaceous (oil) glands Merocrine Most common accumulate their secretory product at the apical surface of each cell, which then separates from the remainder to form a secretion in the lumen of the gland. cells then repair themselves. Ex: Salivary glands
Glandular Epithelium
Connective Tissue Support & strengthen & provide structure
Connective Tissue Found everywhere in the body Includes the most abundant and widely distributed tissues Functions Binds body tissues together Supports the body Provides protection Insulates to maintain body temperature Transportation of other molecules
Origin of Connective Tissue Mesenchyme: embryonic tissue that differentiates into all forms of CT
Connective Tissue Characteristics Variations in blood supply Some tissue types are well vascularized Adipose danger of hemorrhage with liposuction Some have poor blood supply or are avascular Blood supply is necessary for healing brings oxygen & spare parts
Extracellular Matrix Two main elements Ground substance proteins and polysaccharide molecules function as a molecular sieve to diffuse nutrients & other substances Fibers Produced by the cells Three types Collagen fibers tensile strength Elastic fibers stretch with recoil Reticular fibers - support
Connective Tissue Cells Prefixes Fibro Osteo Chondro Hemo(cyto) Suffixes Blast build the cells Cyte cell Clast breakdown the cells
Connective Membranes Synovial Lines spaces between bone and joint Secrete synovial fluid to reduce friction
Connective Tissue Outline Bone Cartilage Hyaline Fibrocartilage Elastic Perichondrium Fibrous Areolar (Loose connective) Adipose Reticular Dense fibrous Regular Irregular Blood Plasma Cells Eryhtrocytes Leukocytes Thrombocytes
Connective Tissue Types - BONE Bone (osseous tissue) Composed of: Bone cells in lacunae (cavities) Hard matrix of calcium salts Large numbers of collagen fibers Osteon primary anatomical and functional unit of compact bone Used to protect and support the body Hematopoiesis formation of blood cells
Connective Tissue Types - CARTILAGE Hyaline cartilage Most common cartilage Composed of: Abundant collagen fibers Rubbery matrix Avascular Found in Entire fetal skeleton Ventral ends of ribs Articular surface of bones
Connective Tissue Types - CARTILAGE Fibrocartilage Highly compressible Strongest & most durable forms cushion-like discs between vertebrae, pubic symphysis, meniscus
Connective Tissue Types - CARTILAGE Elastic cartilage Provides elasticity, very flexible Supports the external ear, larynx
Connective Tissue Types - CARTILAGE Perichondrium Surrounds cartilage
Connective Tissue Types - FIBROUS Areolar (Loose Connective) Most widely distributed connective tissue (surrounds blood vessels & nerves) Soft, pliable tissue Contains all fiber types Can soak up excess fluid Main function to cushion and protect organs Types of fibers Collagenous - collagen Elastic elastin, stretchable Reticular very thin
Connective Tissue Types - FIBROUS Adipose Matrix is an areolar tissue in which fat globules predominate Many cells contain large lipid deposits Functions Insulates the body Protects some organs Serves as a site of fuel storage
Connective Tissue Types - FIBROUS Adipose
Connective Tissue Types - FIBROUS Reticular Delicate network of interwoven fibers Holds together adipose tissue Forms stroma (internal supporting network) of lymphoid organs; soft skeleton Lymph nodes Spleen Bone marrow
Connective Tissue Types - FIBROUS Dense fibrous Main matrix element is collagen fibers Cells are fibroblasts Irregular not parallel dermis Regular - parallel Tendons attach muscle to bone Ligaments attach bone to bone Regular Irregular
Connective Tissue Types - FIBROUS
Connective Tissue Types - BLOOD Fibers are visible during clotting Functions as the transport vehicle for materials 55% Liquid component plasma 45% Blood cells Erythrocytes - RBC Leukocytes - WBC Thrombocytes - platelets
Connective Tissue Outline Bone Cartilage Hyaline Fibrocartilage Elastic Perichondrium Fibrous Areolar (Loose connective) Adipose Reticular Dense fibrous Regular Irregular Blood Plasma Cells Eryhtrocytes Leukocytes Thrombocytes
Muscle Tissue Highly vascular & highly cellular Less matrix = more flexibility More blood flow = more ATP made Actin & myosin contractile myofilaments Function is to produce movement 3 types Skeletal Smooth Cardiac
Muscle Tissue Types Skeletal muscle Can be controlled voluntarily Cells attach to connective tissue Cells are striated Cells have more than one nucleus attached to bone Smooth muscle Involuntary muscle Surrounds hollow organs Attached to other smooth muscle cells No visible striations One nucleus per cell Viscera of hollow internal organs
Muscle Tissue Types Cardiac muscle Found only in the heart Function is to pump blood (involuntary) Cells attached to other cardiac muscle cells at intercalated disks Cells are striated One nucleus per cell
Nervous Tissue Consists of brain, spinal cord, nerves Carry electrical signals Neurons: generate & conduct electricity Usually nonregenerative Neuroglia: support neurons
Tissue Repair Determination of type of repair Type of tissue damaged Severity of the injury Regeneration Replacement of destroyed tissue by the same kind of cells Fibrosis Repair by dense fibrous connective tissue (scar tissue)
Regeneration of Tissues Regenerate easily Epithelial tissue Bone Regenerate poorly Skeletal muscle replaced with connective tissue, not muscle Cartilage Nervous Replaced largely with scar tissue Cardiac muscle Nervous tissue within the brain and spinal cord Connective - keloids
Steps of Tissue Repair 1. capillaries dilate brings blood to supply clotting factors 2. clot forms seal off injury 3. scab forms protect injury 4. debris is cleaned out macrophages eat away damaged tissue to leave room for repair 5. Organization of tissue parts granulation occurs (a type of intermediate tissue) 6. Macrophages digest & remove original clot 7. Surface epithelium regenerates scab usually falls off at this time End result: Healed injury!
Tissue Disease