Chapter 3 Body Tissues

• Epithelial (epithelium) Tissue – Epithet = laid on, covering – Lining, covering, glandular – Functions: protection, absorption, filtration, secretion – Characteristics • Fit closely forming continuous sheets • Apical surface – 1 free surface – exposed to body’s exterior/interior • Lower surface rests on basement membrane – secreted by the cells • Avascular – no blood supply of their own – Depend on diffusion • Regenerate

– 2 names – based on # of layers and cell shape – Simple epithelia – one layer • Simple squamous (fish scale) – Allow rapid diffusion – air sacs, capillaries – Produce serous membranes (serosae) – line ventral body cavity • Simple cuboidal (cube shaped) – Glands and their ducts – salivary, pancreas – Kidney tubule walls – Ovary surface

• Simple columnar (columns) – Goblet cells – produce lubricating mucus – Line digestive tract – Mucus membranes (mucosae) – line body cavities that open to exterior • Pseudostratified columnar – Different heights – Line respiratory tract – May have cilia

– Stratified epithelia – 2 or more cell layers • Stratified squamous – Most common – Esophagus, mouth, outer skin (friction areas) – Free edge – squamous – Basement membrane – cuboidal or columnar

• Stratified cuboidal & Stratified columnar – Rare – Ducts of large glands • Transitional – Modified stratified squamous – allow much stretching – Urinary bladder, ureters, part of urethra

– Glandular epithelium • Glands – 1 or more cells that make and secrete a particular product – Endocrine glands » Ductless glands » Secretions diffuse directly into blood vessels » Ex. thyroid, adrenals, pituitary – Exocrine glands » Have ducts » Secretions empty directly on epithelial surface » Ex. sweat, oil, liver, pancreas

• Connective tissue – Most abundant – Protection, support, binding – Characteristics • Variation in blood supply – lower supply = slower healing

• Extracellular matrix – nonliving substance bound outside cell produced by connective tissue – 2 main elements 1.Ground substance » Water, adhesion proteins, polysaccharides » Fluid, gel-like, rock hard » Adhesion proteins – glue – attaches connective tissue to matrix fibers » Absorbs large amounts of water – reservoir 2. Fibers » Collagen – white – high tensile strength » Elastic – yellow – stretch/recoil » Reticular – internal skeleton of soft organs (spleen)

– Functions: forms soft packing tissue, bears weight, w/stand stretching/abrasions – Ex. Fat tissue – many cells – soft matrix – Ex. Bone/cartilage – few cells – hard matrix – Types – based on differences in fiber type and fiber # – Bone – osseous tissue • Bone cells in cavities (lacunae) • Surrounded by hard matrix w/ calcium salts and lots of collagen • Support, protection

– Cartilage • Hyaline cartilage – Most widespread – Abundant collagen, rubbery matrix – Ex. Surrounds larynx, attaches ribs to breastbone, covers ends of bones – Prenatal skeleton – replaced by bone by birth • Fibrocartilage – cushioning disks of spinal cord • Elastic cartilage – elasticity – ear

– Dense connective tissue (dense fibrous tissue) • Collagen fibers • Tendons – attach muscles to bone • Ligaments – attach bone to bone • Dermis – lower layer of skin

– Loose connective tissue • More cells and fewer fibers • Areolar tissue – Most widely distributed connective tissue – Cushions/protects body organs – Universal packing tissue – Glues internal organs together – Lamina propria – under all mucous membranes – Water/salt reservoir – Edema – swelling caused by collecting excess fluid – Phagocytes

• Adipose tissue (fat) – Signet ring cells – contain large oil droplet that pushes nucleus to side – Subcutaneous tissue under skin » Insulates/prot ects – Fat deposits – hips, breasts

• Reticular connective tissue – Forms stroma (bed) in lymph nodes, spleen, bone marrow

– Blood (vascular tissue) • Blood cells surrounded by nonliving, fluid matrix (plasma) • Fibers are only seen during clotting

• Muscle tissue – Contract and shorten – Skeletal muscle • Attached to skeleton • Voluntary control • Pulls on bone or skin – movement • Multinucleate • Striations • Cells aka muscle fibers because their elongated

– Cardiac muscle • Only in heart • Involuntary control • Uninucleate • Striations • Intercalated disks – where branching cells fit together – contain gap junctions

– Smooth muscle (visceral muscle) • No striations • Spindle shaped • Found in walls of hollow organs – stomach, blood vessels • Contraction – cavity smaller • Relaxation – cavity larger • Ex. Peristalsis – small intestines

• Nerve tissue – Neurons – nerve cells – 2 characteristics: irritability and conductivity – Cytoplasm drawn into long processes

Tissue Repair

– Inflammation – nonspecific – attempts to prevent further injury – Immune responses – attacks specific invaders – Repair (healing) • Regeneration – replacement of cells • Fibrosis – repair by fibrous connective tissue – scar tissue – Type of repair determined by • Type of tissue damaged • Severity of damage

– Process • Capillaries become permeable – Allow clotting to occur – Stop blood loss, holds wound edges, walls of injured area • Granulation tissue forms – Composed largely of new capillaries – Contain phagocytes – dispose of clot and scar tissue • Surface epithelium regenerates – Grows under scab – Scar may be visible – depends on severity of wound – Epithelial and connective tissues regenerate well.

– Muscle and nervous may not regenerate at all.

Tissue Development

– Neoplasm – loss of control over cell division • May be benign or malignant – Hyperplasia – cells multiply due to an irritant or condition • Ex. Breast enlargement due to pregnancy – Atrophy – decrease in size – not used or loses nerve supply