CHAPTER 3 Body Tissues 4 types Epithelial epithelium

CHAPTER 3 Body Tissues (4 types)

Epithelial (epithelium) ■ Epithet = laid on, covering Tissue ■ 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 ■ Modified for function – Lower surface rests on basement membrane – nonliving, secreted by the cells – Avascular – no blood supply of their own ■ Depend on diffusion – Regenerate easily

■ 2 names – based on # of layers and cell shape ■ Simple epithelia – one layer – Simple squamous (fish scale) ■ Allow rapid diffusion – air sacs, capillaries ■ Filtration ■ 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 – scattered w/in – produce lubricating mucus ■ Line digestive tract, uterus ■ Mucus membranes (mucosae) – line body cavities that open to exterior – Pseudostratified columnar ■ Different heights ■ Line respiratory tract ■ May have cilia ■ Mucus traps dust

■ Stratified epithelia – 2 or more cell layers – Stratified squamous ■ Most common ■ Esophagus, mouth, outer skin (friction areas) ■ Free edge – squamous ■ Sits on a basement membrane – cuboidal or columnar

– Stratified cuboidal & Stratified columnar ■ Rare ■ Ducts of large glands (mammary, sweat, salivary); male urethra – Transitional ■ Modified stratified squamous – allow much stretching ■ Urinary bladder, ureters, part of urethra

■ Glandular epithelium – Found w/in columnar & cuboidal – 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

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 – Absorbs large amounts of water – reservoir

2. Protein Fibers – Collagen – white – high tensile strength – resist high pulling forces – Elastic – yellow – stretch/recoil – resume shape – Reticular – internal skeleton of soft organs (spleen) ■ Connective tissue 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 (glassy) ■ 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; epiglottis

■ Dense connective tissue (dense fibrous tissue, white 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 ■ Water/salt reservoir ■ Edema – swelling caused by collecting excess fluid

– Adipose tissue (fat) ■ Signet ring cells – Contain large oil droplet that pushes nucleus to side ■ Subcutaneous tissue under skin – Insulates/ protects ■ 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 they’re 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, bladder – 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) – 2 types – (1) Regeneration – replacement of cells – (2) 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 ■ Cell differentiation – process of specialization – Stem cells – are not specialized yet – may become a number of types ■ Neoplasm – loss of control over cell division – May be benign or malignant – Invasiveness – can break through boundaries – Angiogenesis – can induce growth of blood vessels to insure movement of nutrients/wastes – Metastasis – spread to other areasthrough blood/lymph ■ 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