tissues recall: the cell tissues groups of interconnected cells working together to fuzz derivation of cells anatomy trains

Transcription

1 recall: the cell cell smallest, metabolically functional unit of body 200+ different types of tissues cells exist in the human body each specialized for a specific function tissues groups of interconnected cells working together to fuzz perform a specific function study of tissues is called histology 4 basic types of tissues exist: epithelial connective muscle nervous derivation of cells anatomy trains tissues are derived from 3 distinct layers of cells during embryonic development primary germ layers v=zyu7ssqmvre&feature=related

2 endoderm gives rise to our inner most structures: epithelium lining respiratory and digestive tract tissue of liver and pancreas mesoderm gives rise to: muscle tissue ALL connective tissues reproductive and excretory organs ectoderm gives rise to: epidermis central nervous system epithelium tissue composed of a layer of cells covering/lining body surface function: protection absorption filtration excretion secretion sensory reception 1. protection protects exposed and internal surfaces from: abrasion/friction water loss invasion of organisms ex. epidermis of skin covered with dead cells filled with hydrophobic, hard keratin protein: limits water loss selective barrier allows specific items in tight junctions between cells allows movement of substance through the cells only transepithelia transport 2. absorption

3 3. filtration prevents movement of some specific items 5. secretion water-based fluid is discharged from a cell may contain protein, lipids needed substances are obtained from blood and chemically altered and released to be used by the body 4. excretion removing wastes from the body undigestible food residue urine CO2 6. sensory reception highly innervated by sensory nerves act as a surveyor of external world! individual cells (goblet cells) interspersed throughout regular cells collections of gland cells (glands) 1. Polarity has 2 surfaces: apical exposed surface facing lumen/ exterior usually has microvilli basal in contact with a basement membrane/basal lamina 2. specialized contacts cells are closely-packed to form continuous sheets adjacent cells are joined together at many points by lateral contacts: tight junctions desmosomes have little extracellular material between them

4 3. supported by connective tissue reinforced by a basement membrane (basal lamina and reticular lamina) glycoproteins and collagen networks 4. avascular but innervated does not have blood supply...avascular located on the basal surface of nutrients come from helps to: reinforce epithelia sheet resist stretching, tearing forces define epithelia boundaries connects to underlying does have a nerve the cell underlying CT supply...innervated connective tissue 5. continuously replace themselves due to damage/loss friction, bacteria, acids, smoke type and classification of epithelia epidermis replaced fully every 2 weeks lining of gut replaced every 2 days major types 2 major types: covering and lining epithelia covers body surfaces lines body cavities/ lumens glandular epithelia forms glands of body classification of epithelia a. Number of Layers simple: single layer absorption and filtration blood vessels, kidney, intestine stratified: 2 or more layers high abrasion areas skin, mouth

5 classification of epithelia b. Shape 3 main types: squamous (flat) cuboidal (boxlike) columnar (tall, column-shaped) named according to apical layer shapes vary among layers simple squamous simplest single layer of flattened cells disc shaped central nuclei function: allows passage of material filtration or diffusion location: kidney filtration membrane air sacs/alveoli in lungs lines heart and blood vessels endothelium lines ventral body cavities and covers organs mesothelium simple cuboidal single layer of cube-like cells large spherical central nuclei function: secretion and absorption location: kidney tubules ducts of glands ovaries single layer of tall cells round to oval nuclei some have cilia may have goblet cells function: absorption (microvilli) simple columnar secretion of mucus, enzymes (goblet cells) may move mucus (cilia) location: digestive tract uterus/bronchi (ciliated) stratified squamous composed of several layers basal cells are cuboidal/columnar mitotically active replenish superficial cells surface cells are: squamous dead far from nutrient supply keratinized or nonkeratinized tough protein stomach mucosa

6 stratified squamous function: protection of underlying tissue in areas of friction location: linings of: mouth, pharynx esophagus anal canal vagina epidermis of skin stratified cuboidal rare sweat glands esophagus rare pharynx stratified columnar pseudostratified columnar epithelia single layer of cells of differing heights ciliated/non-ciliated variety some do not reach free surface but ALL touch basal layer nuclei seen at different levels may contain goblet cells function: absorption and secretion location: sperm ducts (non cliliated) trachea (ciliated) trachea transitional epithelia resembles both stratified squamous and stratified cuboidal ex. when bladder is full and stretched, cuboidal cells look squamous function: stretch readily and permit distention location: lines: ureter bladder part of urethra gland: glandular epithelium one or more epithelial cells that make and secrete substances: into ducts onto surface into bloodstream product is called a secretion aqueous fluid that usually contains proteins

7 function secretion is an active process cells obtain needed substances from blood transform them chemically into product to be discharged classification of glands routes of secretion: exocrine (externally secreting) endocrine (internally secreting) number of cells making up the gland: unicellular multicellular exocrine vs endocrine exocrine may or may not have a duct secret products: into body cavities onto free surfaces sweat, salivary, liver, pancreas, mammary glands endocrine ductless products enter ECF and diffuse into blood/lymph...travel to target pituitary, thyroid, adrenal, pancreas secrete hormones single cells unicellular exocrine between columnar or pseudostratified columnar epithelial cells in intestinal and respiratory tract no duct secrete onto free surface secrete mucus complex glycoprotein protects and lubricates goblet cells digestive respiratory reproductive systems multicellular exocrine structurally more complex 2 main features: duct epithelium-derived secretory unit with secretory cells structural classification of multicellular simple glands: have a single unbranched duct compound glands: have a branching duct

8 further classification by secretory units tubular: secretory cells forming a tube alveolar: secretory cells forming small, flask-like sacs (hollow cavity) tubuloalveolar: consists of both tubular and alveolar secretory units functional classification multicellular exocrine glands secrete their products in different ways can be described functionally: merocrine holocrine secrete by exocytosis secreting cells are not altered pancreas, sweat glands, salivary glands merocrine holocrine accumulate product in cytosol cell divides, then dies and contents discharged sebaceous (oil) glands of skin