Transcript Tissues
Tissues Chapter 4 Klennex isn’t the Only Tissue • Tissues are groups of cells with similar structures and functions – Histology studies them • 4 primary types – Epithelial – covering and boundary formation – Connective – support, protect, and bind – Muscle – contractions cause movement – Nervous - control and communication • Organs often composed of all 4 Embryonic Development • Zygote cleaves to become a blastocyst that undergoes gastrulation – Humans have 3 primary germ layers – 2nd- 3rd week • Germ layers – Ectoderm • Epidermis and nervous system – Endoderm • Linings of digestive and respiratory tracts – Mesoderm • Skeletal, muscular, and circulatory systems Epithelial Tissue • Covers or lines cavities/surfaces • Forms glands too • Functions reflect structure – Protection, absorption, filtration, excretion, secretion, sensory reception, and gas exchange • Characteristics – Cellularity: cells packed tight together, bound by tight junctions and desmosomes – Polarity • Apical and basal surfaces – Connective tissue attachment • Basal lamina (noncellular) to reticular lamina (ECM) = basement membrane • Resists stretching and tearing – Avascular, but innervated – Regeneration • Friction and external substance exposure Classifying/Naming Epithelia Layer Shape • Simple: 1 • Nuclei shape and apical layer – Absorbtion, secretion, and filtration • Squamous: flattened, scale• Stratified: 2+ like – Protection • Cuboidal: sides equal, box-like • Pseudostatified: looks 2+, but not • Columnar: taller than wide • Transitional: varies Simple _______ Epithelia • Columnar – Possibly goblet cells, microvilli, and/or cilia – Digestive tract, and gland ducts; small bronchi, uterine tubes, and uterus – Absorption, secretion of mucus, cilia propels substances • Cuboidal – Kidney tubules, ducts of glands, and ovary surface – Secretion and absorption • Squamous – Kidney glomeruli, air sacs of lungs, capillaries, linings of heart & lymphatic system, serous membranes – Diffusion and filtration; secretes lubricant Additional Epithelia • Pseudostratified columnar – Possible goblet cells and cilia – Male repo. tracts; respiratory tract – Secretion and propulsion via cilia • Stratified squamous – Apically, basally cuboidal (living cells); may be keratinized – Surfaces that are exposed externally and into all openings – Protect abrasive surfaces • Transitional epithelium – Cuboidal and columnar basally, squamous apically as urine volume increases – Urinary system (except kidneys) – Change as bladder collects and excretes Glandular Epithelia • Endocrine – Ductless • Release hormones by exocytosis into blood – Acts on target organ(s) • Exocrine – Possess ducts • Secretions onto body surface or within cavities – Cellularity • Unicelluar: goblet cells produce mucin • Multicellular – Simple (unbranched): gastric and sebaceous – Compound (branched): duodenal, mammary, and salivary – 1 or 2 secretion modes • Merocrine: exocytosis; pancreas and sweat &most others • Apocrine: accumulate at apex & pinches off; mammary (?) • Holocrine: accumulate and rupture; sebaceous Connective Tissue • Never exposed to environment outside the body • Functions – Protect, insulate, transport, support, and bind other tissues together • Characteristics – Composed of multiple cell types • Mesenchyme origin – Range of vascularity – Primarily extracellular matrix (ECM) • Non-living; responsible for CT strength and abrasion CT Structure • Ground substance – Unstructured space filler • Liquid, gel-like, or solid • Fibers – Collagen: tough with lots of collagen protein; white fibers – Elastic: flexible and stretchable with lots of elastin protein; yellow fibers – Reticular: add extra support with collagen and glycoprotein • Cells (-blast or –cyte) – – – – FibroChondroOsteoHematopoietic stem cell Connective Tissue Classification Connective tissues Fluid CT CT Proper Blood: in circulatory system Loose: Fibers loose, open; i.e. adipose Dense: Fibers densly packed; i.e. tendons • Bold = 4 main types Supporting CT Lymph: in lymphatic system Cartilage: solid, rubbery matrix Bone: solid, crystalline matrix • Areolar Loose CT – Matrix with all 3 fibers and multiple cells – Widely distributed throughout the body – Lubricates and nourishes epithelia; strength; elasticity; support; immune protection • Edema: inflammatory swelling of liquids • Adipose – Little matrix or fibers, but stores more nutrients – Subcutaneous layer; around organs • Brown vs white fat – Stores triglycerides; insulates; energy reserve; protects • Reticular – Similar to areolar, but only reticular fibers – Liver; spleen; lymph nodes – Support and slow body fluids Dense CT • Dense regular – Mostly parallel collagen fibers, some elastic • Wavy for direction of stretch – Attaches muscle to bone (tendon), muscle to muscle (aponeuroses), bone to bone (ligament) – Resists tension (1 direction), support, and stabilization • Irregular dense – Collagen is thicker and not parallel – Dermis; joint and organ capsules – Resists tension (multiple directions) Cartilage • • • • Avascular w/o innervations Mostly water respond to compression Chondroblasts and chondrocytes in lacunae Hyaline (gristle) – Most abundant, mainly collagen fibers – Articular surfaces, embryonic skeleton; costal cartilage; septum; respiratory system – Support with pliability; compressive stress • Elastic – More elastic fibers than hyaline – External ear and epiglottis – Shape and flexibility • Fibrocartilage – Less firm than hyaline; thick collagen fibers and chondrocytes – Intervertebral discs; knee joint; pubic symphysis – Resist compression; absorb shock; prevent bone rubbing Osseous Tissue • Collagen fibers and calcium salts • Osteoblasts make matrix and deposited salts solidify • Osteon – Lamella – Lacunae • Osteocytes maintain bone • Osteoclasts breakdown bone – Canaliculi • Compact or spongy Blood • No connections or mechanical support • 55% plasma (matrix) – 90% water • 45% cellular components – Erthrocytes – Leukocytes – Thrombocytes Nervous Tissue • Generate and conduct impulses = communication • Most incapable of dividing • Neurons – Cell body – Processes • Axon • Dendrites • Neuroglia • Central and peripheral nervous system Muscle Tissue • Cellular and vascularized • Found through the body • Responsible for movements – Myofilaments • Skeletal – Striated, multinucleate, voluntary – Moves body parts – Can’t divide, but partial regeneration • Cardiac – – – – Striated, uninucleate, involuntary Branched with intercalated discs In heart Can’t divide or regenerate • Smooth – No striations, uninucleate, involuntary – Moves substance (object) along – Can divide Membranes • Cutaneous – Exterior exposure; dry – Keratinized stratified squamous and dense irregular CT • Mucous – Exterior opening cavities; ‘moist membranes’ – Stratified squamous or simple cuboidal and loose CT • Serous – Line ventral body cavity; moist membranes – Simple squamous and loose CT