Tissue Level of Organization PDF

The Tissue Level of Organization Aaron Opoku Antwi, PhD. Dept. of Pharmacology Ist Floor, New Pharmacy Block Tissue ▷ Group of similar cells and cell products that arise from the same region of the embryo and work together to perform a specific structural or physiological role in an organ...

The Tissue Level of Organization Aaron Opoku Antwi, PhD. Dept. of Pharmacology Ist Floor, New Pharmacy Block Tissue ▷ Group of similar cells and cell products that arise from the same region of the embryo and work together to perform a specific structural or physiological role in an organ 2  Origin of Tissues Primary germ layers within the embryo – endoderm – mesoderm – ectoderm Tissue derivations – epithelium from all 3 germ layers – connective tissue & muscle from mesoderm – nerve tissue from ectoderm 3 Tissues ▷ Group of similar cells ○ common embryonic origin ○ common function ▷ Histology ○ study of tissues ▷ Pathologist ○ looks for tissue changes that indicate disease; forensic pathology?? 4 Tissues ▷ Biopsy Removal of living tissue for microscopic examination – surgery – needle biopsy Useful for diagnosis, especially cancer Tissue preserved, sectioned and stained before microscopic viewing; micrographs? 5 6 7 Cell Junctions ▷ Points of contact between adjacent plasma membranes. ▷ Depending on their structure, cell junctions may serve one of three functions. ○ form fluid-tight seals between cells. ○ anchor cells together or to extracellular material. ○ act as channels, which allow ions and mol. to pass from cell to cell within a tissue 8 Cell Junctions Tight junctions Adherens junctions Gap junctions Desmosomes Hemidesmosomes 9 Tight Junctions Watertight seal between cells Plasma membranes fused with a strip of proteins Common between cells that line GI and bladder 10 Adherens Junctions Holds epithelial cells together Structural components – plaque = dense layer of proteins inside the cell membrane – microfilaments extend into cytoplasm – integral membrane proteins connect to membrane of other cell 11 Gap Junctions Tiny space between plasma membranes of 2 cells Crossed by protein channels called connexons forming fluid filled tunnels Cell communication with ions & small molecules Muscle and nerve impulses spread from cell to cell – heart and smooth muscle of gut 12 Desmosomes Resists cellular separation and cell disruption Similar structure to adherens junction except intracellular intermediate filaments cross cytoplasm of cell Cellular support of cardiac muscle 13 Hemidesmosomes Half a desmosome Connect cells to extracellular material – basement membrane 14 4 Basic Types of Tissues They differ in: ▷ Epithelial Tissue 1. Types of cells ▷ Connective Tissue 2. Functions OF cells ▷ Muscle Tissue 3. C’tics of matrix surrounding cells ▷ Nerve Tissue 4. Ratio of cells to matrix 15  EPITHELIAL TISSUE ❑ contact “ covers surfaces because cells are in ❑ lines hollow organs, cavities and ducts ❑ forms glands when cells sink under the surface 16 General Features ▪ Closely packed cells forming continuous sheets ▪ Cells sit on basement membrane ▪ Apical (upper) free surface ▪ Avascular---without blood vessels ▪ nutrients diffuse in from underlying connective tissue ▪ Good nerve supply ▪ Rapid cell division ▪ Covering / lining versus glandular types 17 Basement Membrane ▪ Basal lamina ▪ from epithelial cells ▪ collagen fibers ▪ Reticular lamina ▪ secreted by connective tissue cells ▪ reticular fibers ▪ holds cells to connective tissue ▪ guide for cell migration during development 18 Types of Epithelium ▪ Covering and lining epithelium ▪ epidermis of skin ▪ lining of blood vessels and ducts ▪ lining respiratory, reproductive, urinary & GI tract ▪ Glandular epithelium ▪ secreting portion of glands ▪ thyroid, adrenal, and sweat glands 19 Classifiction of Epithelium ▪ Classified by arrangement of cells into layers ▪ simple = one cell layer thick ▪ stratified = many cell layers thick ▪ pseudostratified = single layer of cells where all cells don’t reach apical surface ▪ nuclei at found at different levels so it looks multilayered 20 Classifiction of Epithelium ▪ Classified by shape of surface cells ▪ squamous =flat ▪ cuboidal = cube-shaped ▪ columnar = tall column ▪ transitional = shape varies with tissue stretching 21 Epithilium 22 Simple Squamous Epithelium ▪ Single layer of flat cells ▪ lines blood vessels (endothelium), body cavities (mesothelium) ▪ very thin --- controls diffusion, osmosis and filtration ▪ nuclei centrally located ▪ Cells in direct contact with each other 23  Examples of Simple Squamous ▪ Surface view of lining ▪ Section of intestinal of peritoneal cavity showing serosa 24 Simple Cuboidal Epithelium ▪ Single layer of cube-shaped cells viewed from the side ▪ Nuclei round and centrally located ▪ Lines tubes of kidney ▪ Absorption or secretion 25  Example of Simple Cuboidal ▪ Sectional view of kidney tubules 26 Simple Cuboidal Epithelium ▪ Single layer of cube-shaped cells viewed from the side ▪ nuclei are round and centrally located ▪ lines tubes of kidney ▪ adapted for absorption or secretion 27 Nonciliated Simple Columnar ▪ Single layer rectangular cells ▪ Unicellular glands =goblet cells secrete mucus ▪ lubricate GI, respiratory, reproductive and urinary systems ▪ Microvilli = fingerlike cytoplasmic projections ▪ for absorption in GI tract (stomach to anus) 28 Eg. Nonciliated Simple Columnar ▪ Section from small intestine 29 Nonciliated Simple Columnar ▪ Single layer rectangular cells ▪ Unicellular glands (goblet cells) secrete mucus ▪ lubricate GI, respiratory, reproductive and urinary systems ▪ Microvilli (non-motile, fingerlike membrane projections) ▪ adapted for absorption in GI tract (stomach to rectum 30 Ciliated Simple Columnar Epithelium ▪ Single layer rectangular cells with cilia ▪ Mucus from goblet cells moved along by cilia ▪ found in respiratory system and uterine tubes 31 Eg. Ciliated Simple Columnar ▪ Section of uterine tube 32  Pseudostratified Columnar Single cell layer All cells attach to basement membrane but not all reach free surface Nuclei at varying depths Respiratory system, male urethra & epididymis 33  Stratified Squamous Epithelium ▪ Several cell layers thick ▪ Surface cells flat ▪ Keratinized = surface cells dead and filled with keratin ▪ skin (epidermis) ▪ Nonkeratinized = no keratin in moist living cells at surface ▪ mouth, vagina 34 Example of Stratified Squamous Section of vagina 35 Papanicolaou Smear (Pap smear) Collect sloughed off cells of uterus and vaginal walls Detect cellular changes (precancerous cells) Annually for women over 18 or if sexually active 36 Ciliated Simple Columnar Epithelium ▪ Single layer rectangular cells with cilia ▪ Unicellular glands (goblet cells) secrete mucus ▪ Cilia (motile membrane extensions) move mucous ▪ found in respiratory system and in uterine tubes 37 Stratified Cuboidal Epithelium Multilayered Surface cells cuboidal – rare (only found in sweat gland ducts & male urethra) 38  Stratified Columnar Epithelium ▪ Multilayered ▪ Surface cells columnar ▪ Rare (very large ducts & part of male urethra) 39  Transitional Epithelium ▪ Multilayered ▪ Surface cells varying in shape from round to flat if stretched ▪ Lines hollow organs that expand from within (urinary bladder) 40 Glandular Epithelium Derived from epithelial cells that sank below the surface during development Exocrine glands – cells that secrete---sweat, ear wax, saliva, digestive enzymes onto free surface of epithelial layer – connected to the surface by tubes (ducts) – unicellular glands or multicellular glands Endocrine glands – secrete hormones into the bloodstream – hormones help maintain homeostasis 41  Structural Classification of Exocrine Glands Unicellular are single-celled glands – goblet cells Multicellular glands – branched (compound) or unbranched (simple) – tubular or acinar (flask-like) shape 42 Examples of Simple Glands Unbranched ducts = simple glands Duct areas are blue 43 Examples of Compound Glands Which is acinar? Which is tubular? 44 Duct of Multicellular Glands Sweat gland duct Stratified cuboidal epithelium 45 Simple Cuboidal Epithelium 46  CONNECTIVE TISSUE “ ❑ material found between cells ❑ supports and binds structures together ❑ stores energy as fat ❑ provides immunity to disease 47 Connective Tissue 48  Connective Tissue Comprises a different array of : Cells (fibroblasts, mast cells, plasma cells etc.) Fibres (collagen, reticular and elastin) Ground substance (chondroitin sufate, fibronectin etc.) 49  Cell Types Blast type cells = retain ability to divide & produce matrix (fibroblasts, chondroblasts, & osteoblasts) Cyte type cells = mature cell that can not divide or produce matrix (chondrocytes & osteocytes) Macrophages develop from monocytes – engulf bacteria & debris by phagocytosis Plasma cells develop from B lymphocytes – produce antibodies that fight against foreign substances Mast cells produce histamine that dilate small BV Adipocytes (fat cells) store fat 50  Tissue Fiber types Collagen (25% of protein in your body) – tough, resistant to pull, yet pliable – formed from the protein collagen Elastin (lungs, blood vessels, ear cartilage) – smaller diameter fibers formed from protein elastin surrounded by glycoprotein (fibrillin) – can stretch up to 150% of relaxed length and return to original shape Reticular (spleen and lymph nodes) – thin, branched fibers that form framework of organs – formed from protein collagen 51  Clinical note: Marfan Syndrome Inherited disorder of fibrillin coding gene Abnormal development of elastic fibers Tendency to be tall with very long legs, arms, fingers and toes Life-threatening weakening of aorta may lead to rupture 52  Ground Substance Supports the cells and fibers Helps determine the consistency of the matrix – fluid, gel or solid Contains many large molecules – hyaluronic acid is thick, viscous and slippery – condroitin sulfate is jellylike substance providing support – adhesion proteins (fibronectin) binds collagen fibers to ground substance 53  Types of Connective tissue Fibrous Connective tissue Reticular, areolar and Adipose (fat) Supportive Connective tissue Bone and cartilage Fluid connective tissue blood and lymph 54 Fibrous Connective Tissue Loose connective tissue Dense connective tissue 55 Loose Connective Tissues Loosely woven fibers throughout tissues Types of loose connective tissue – areolar connective tissue – adipose tissue – reticular tissue 56  Areolar Connective Tissue Cell types = fibroblasts, plasma cells, macrophages, mast cells and a few white blood cells All 3 types of fibers present Gelatinous ground substance 57 Areolar Connective Tissue Black = elastic fibers, Pink = collagen fibers Nuclei are mostly fibroblasts 58  Adipose Tissue Peripheral nuclei due to large fat storage droplet Deeper layer of skin, organ padding, yellow marrow Reduces heat loss, energy storage, protection Brown fat found in infants has more blood vessels and mitochondria and responsible for heat generation 59 Liposuction or Suction Lipectomy Suctioning removal of subcutaneous fat for body contouring Dangers include fat emboli, infection, injury to internal organs and excessive pain 60  Reticular Connective Tissue Network of fibers & cells that produce framework of organ Holds organ together (liver, spleen, lymph nodes, bone marrow) 61  Dense Connective Tissue More fibers present but fewer cells Types of dense connective tissue – dense regular connective tissue – dense irregular connective tissue – elastic connective tissue 62 Dense Regular Connective Tissue Collagen fibers in parallel bundles with fibroblasts between bundles of collagen fibers White, tough and pliable when unstained (forms tendons) Also known as white fibrous connective tissue 63 Dense Irregular Connective Tissue Collagen fibers are irregularly arranged (interwoven) Tissue can resist tension from any direction Very tough tissue -- white of eyeball, dermis of skin 64 Elastic Connective Tissue Branching elastic fibers and fibroblasts Can stretch & still return to original shape Lung tissue, vocal cords, ligament between vertebrae 65  Supportive: Cartilage Network of fibers in rubbery ground substance Resilient and can endure more stress than loose or dense connective tissue Types of cartilage – hyaline cartilage – fibrocartilage – elastic cartilage 66  Hyaline Cartilage Bluish-shiny white rubbery substance Chondrocytes sit in spaces called lacunae No blood vessels or nerves so repair is very slow Reduces friction at joints as articular cartilage 67  Fibrocartilage Many more collagen fibers causes rigidity & stiffness Strongest type of cartilage (intervertebral discs) 68  Elastic Cartilage Elastic fibers help maintain shape after deformations Ear, nose, vocal cartilages 69  Growth & Repair of Cartilage Grows and repairs slowly because is avascular Interstitial growth – chondrocytes divide and form new matrix – occurs in childhood and adolescence Appositional growth – chondroblasts secrete matrix onto surface – produces increase in width 70 Supportive: Bone (Osseous) Tissue Spongy bone – sponge-like with spaces and trabeculae – trabeculae = struts of bone surrounded by red bone marrow – no osteons (cellular organization) Compact bone – solid, dense bone – basic unit of structure is osteon (haversian system) Protects, provides for movement, stores minerals, site of blood cell formation 71  Compact Bone Osteon = lamellae (rings) of mineralized matrix – calcium & phosphate---give it its hardness – interwoven collagen fibers provide strength Osteocytes in spaces (lacunae) in between lamellae Canaliculi (tiny canals) connect cell to cell 72  Fluid: Blood cells (erythrocytes), white blood cells (leukocytes) Connective tissue with a liquid matrix = the plasma Cell types = red blood nd cell fragments called platelets Provide clotting, immune functions, carry O2 and CO2 73  Fluid: Lymph Interstitial fluid being transported in lymphatic vessels Contains less protein than plasma Move cells and substances (lipids) from one part of the body to another 74  Membranes Epithelial layer sitting on a thin layer of connective tissue (lamina propria) Types of membranes – mucous membrane – serous membrane – synovial membrane – cutaneous membrane (skin) 75 Membranes 76  Mucous Membranes Lines a body cavity that opens to the outside – mouth, vagina, anus etc Epithelial cells form a barrier to microbes Tight junctions between cells Mucous is secreted from underlying glands to keep surface moist 77  Serous Membranes Simple squamous cells overlying loose CT layer Squamous cells secrete slippery fluid Lines a body cavity that does not open to the outside such as chest or abdominal cavity Examples – pleura, peritoneum and pericardium – membrane on walls of cavity = parietal layer – membrane over organs in cavity = visceral layer 78  Synovial Membranes Line joint cavities of all freely movable joints No epithelial cells-- -just special cells that secrete slippery fluid 79  MUSCLE TISSUE “ ❑ cells shorten in length producing movement ❑ Provide us with motion, posture and heat 80  Muscle tissue Types of muscle ▷ skeletal muscle ▷ cardiac muscle ▷ smooth muscle 81  Skeletal Muscle ▪ Cells are long cylinders with many peripheral nuclei ▪ Visible light and dark banding (looks striated) ▪ Voluntary or conscious control 82  Cardiac Muscle Cells are branched cylinders with one central nuclei Involuntary and striated 83  Cardiac Muscle Attached to and communicate with each other by intercalated discs and desmosomes 84  Smooth Muscle Spindle shaped cells with a single central nuclei Walls of hollow organs (blood vessels, GI tract, bladder) Involuntary and nonstriated 85  NERVE TISSUE “ ❑ cells that conduct electrical signals ❑ detects changes inside and outside the body ❑ responds with nerve impulses 86  Nerve Tissue Cell types -- nerve cells and neuroglial (supporting) cells Nerve cell structure – nucleus & long cell processes conduct nerve signals dendrite --- signal travels towards the cell body axon ---- signal travels away from cell body 87 Nerve Tissue 88  Tissue Engineering New tissues grown in the laboratory (skin & cartilage) Scaffolding of cartilage fibers is substrate for cell growth in culture Research in progress – insulin-producing cells (pancreas) – dopamine-producing cells (brain) – bone, tendon, heart valves, intestines & bone marrow 89 Tissue Repair: Restoring Homeostasis Worn-out, damaged tissue must be replaced Fibrosis = replacement with stromal connective tissue cells (scar formation) 90 Tissue Repair: Restoring Homeostasis Regeneration = replacement with original cell types (parenchymal cells) – some cell types can divide (liver & endothelium) – some tissues contain stem cells that can divide bone marrow, epithelium of gut & skin – some cell types can not divide & are not replaced muscle and nervous tissue 91 Important Clinical Terminology Regeneration versus fibrosis Granulation tissue – very actively growing connective tissue Adhesions – abnormal joining of tissue – occurs after surgery or inflammation 92 Conditions Affecting Tissue Repair Nutrition – adequate protein for structural components – vitamin C production of collagen and new blood vessels Proper blood circulation – delivers O2 & nutrients & removes fluids & bacteria 93 Conditions Affecting Tissue Repair With aging – collagen fibers change in quality – elastin fibers fragment and abnormally bond to calcium – cell division and protein synthesis are slowed 94  Sjogren’s Syndrome Autoimmune disorder producing exocrine gland inflammation Dryness of mouth and eyes 20 % of older adults show some signs 95 Systemic Lupus Erythematosus (SLE) Autoimmune disorder -- causes unknown Chronic inflammation of connective tissue Nonwhite women during childbearing years Females 9:1 (1 in 2000 individuals) Painful joints, ulcers, loss of hair, fever Life-threatening if inflammation occurs in major organs --- liver, kidney, heart, brain, 96