MHS1101 LECTURE 4 TISSUES OF THE BODY.pptx

MHS1101: LECTURE 4 TISSUES OF THE BODY LEARNING OUTCOMES By the end of this lecture you should be able to:  Name the four primary classes into which all adult tissues are classified  Outline the cells, fibres & ground substance of these tissues  Describe two mechanisms of bone formation  Discus...

MHS1101: LECTURE 4 TISSUES OF THE BODY LEARNING OUTCOMES By the end of this lecture you should be able to:  Name the four primary classes into which all adult tissues are classified  Outline the cells, fibres & ground substance of these tissues  Describe two mechanisms of bone formation  Discuss the hormones involved in calcium metabolism in the body TISSUES OF THE BODY  body has 50 trillion cells of 200 different cell types  tissues - group of similar cells & cell products that perform specific roles in organs  organ - structure with discrete boundaries comprising two or more tissue types  histology (microscopic anatomy) - study of tissues & how they are arranged into organs THE PRIMARY TISSUE CLASSES  Tissues differ with respect to:  characteristics of the surrounding extracellular material or matrix  matrix comprises fibrous proteins & clear gel called ground substance [tissue fluid, extracellular fluid (ECF), interstitial fluid, or tissue gel]  cell types  relative volume of space occupied by cells versus matrix EXAMINING TISSUES  tissues can be processed for examination using light or electron microscope  cut in different planes/sections – longitudinal or cross-section  can look very different in different planes/sections 3D INTERPRETATION OF 2D IMAGES Figure 5.1 ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. LONGITUDINAL, CROSS & OBLIQUE SECTIONS Figure 5.2 ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. THE PRIMARY TISSUE CLASSES Four primary tissues (i) Epithelial (ii) Connective (iii) Nervous (iv) Muscle CELL JUNCTIONS  connections between two cells  most cells are anchored to each other or their matrix  cells communicate with each other, resist mechanical stress & control what moves through the gaps between them Tight Junctions, Desmosomes & Gap Junctions  Tight junctions: linkages between cells by transmembrane cell-adhesion proteins  Desmosome: ’patch’ that holds cells together (like a peg) proteins keep cells from pulling apart - resist mechanical stress  hemidesmosomes: anchor basal region of cells to basement membrane cannot easily peel away from underlying tissues  Gap junctions - transmembrane proteins - ions, nutrients & other small solutes pass between cells TISSUES OF THE BODY: (I) EPITHELIAL TISSUE  forms sheets of closely adhering cells, one or more cells thick  cover body surfaces & line body cavities  upper surface usually exposed to environment or internal space in body  constitutes most glands  avascular  usually nourished by underlying connective tissue EPITHELIAL TISSUE Functions:  protect deeper tissues from injury & infection  excrete wastes  absorb chemicals including nutrients  selectively filter substances  sense stimuli  cells very close together EPITHELIAL TISSUE  high rate of mitosis  basement membrane - layer between epithelium & underlying connective tissue  collagen, proteins, glycoproteins, protein-carbohydrate complexes  anchors the epithelium to the connective tissue below it  basal surface - surface of epithelial cell facing basement membrane  apical surface - surface of epithelial cell facing away from basement membrane TYPES OF EPITHELIAL TISSUE  Simple epithelia  one layer of cells - named according to shape of cells  all cells touch basement membrane  Stratified epithelia  more than one cell layer - named according to shape of apical cells  some cells rest on top of others & do not touch basement membrane  pseudostratified columnar epithelia  appears stratified as some cells taller than others  every cell reaches basement membrane (but not all cells reach free surface)  goblet cells - mucus-secreting cells in simple columnar & pseudostratified epithelia CELL SHAPES & EPITHELIAL TYPES Figure 5.3 ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. SIMPLE SQUAMOUS EPITHELIUM  single layer of thin cells  permits rapid diffusion or transport of substances  secretes serous fluid  locations: alveoli, glomeruli, endothelium Figure 5.4a,b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. SIMPLE CUBOIDAL EPITHELIUM  single layer of square or round cells  absorption & secretion, mucus production & movement  locations: liver, thyroid, salivary glands, bronchioles & kidney tubules a: © McGraw-Hill Education/Dennis Strete, photographer Figure 5.5a, b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. SIMPLE COLUMNAR EPITHELIUM  single row of tall, narrow cells with oval nuclei in basal half of cell  brush border of microvilli, ciliated in some organs, may possess goblet cells  absorption & secretion  locations: lining of GI tract, uterus, kidney, and uterine tubes a: © Ed Reschke/Getty Images Figure 5.6a,b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. PSEUDOSTRATIFIED EPITHELIUM  looks multilayered, but all cells touch basement membrane  nuclei at several layers  cilia & goblet cells  secrete & propel mucus  locations: respiratory tract © McGraw-Hill Education/Dennis Strete, photographer Figure 5.7a,b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. STRATIFIED EPITHELIA  2 - 20 or more layers of cells  some cells rest directly on others  only deepest layer attaches to basement membrane  Three stratified epithelia - named for shapes of apical surface cells  stratified squamous  stratified cuboidal  stratified columnar (rare)  fourth type  transitional epithelium STRATIFIED EPITHELIA  stratified squamous most widespread epithelium in body  deepest layers undergo continuous mitosis  ‘daughter’ cells push towards surface & become flatter as migrate upward  finally die - exfoliated/desquamated  two kinds of stratified squamous epithelia  keratinized - found on skin surface, abrasion resistant  nonkeratinized - lacks surface layer of dead cells KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM  multiple cell layers - cells become flat & scaly toward surface - skin  resists abrasion, retards water loss, resists penetration by pathogenic organisms  locations: epidermis; palms & soles Figure 5.8a,b a: © Ed Reschke ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. NON-KERATINIZED STRATIFIED SQUAMOUS EPITHELIUM  same as keratinized epithelium without surface layer of dead cells  resists abrasion & penetration of pathogens  locations: tongue, oral mucosa, esophagus Figure 5.9a,b a: © Ed Reschke ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. STRATIFIED CUBOIDAL EPITHELIUM  two or more cell layers; surface cells square or round  secrete sweat; produce sperm, produce ovarian hormones  locations: sweat gland ducts; ovarian follicles & seminiferous tubules Figure 5.10a,b a: © Lester V. Bergman/Corbis ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. TRANSITIONAL EPITHELIUM  multilayered epithelium - surface cells change from round to flat when stretched  allows for filling of urinary tract  locations: ureter & bladder Figure 5.11a,b a: © Johnny R. Howze ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. TISSUES OF THE BODY: (II) CONNECTIVE TISSUE  diverse, abundant type of tissue with fewer cells relative to matrix  most cells not in direct contact with each other  supports, connects & protects organs  highly variable vascularity  loose connective tissues have many blood vessels  cartilage has few or no blood vessels CONNECTIVE TISSUE  Functions:  connecting organs - tendons & ligaments  support - bones & cartilage  physical protection - cranium, ribs, sternum  immune protection - white blood cells attack foreign invaders  movement - bones provide lever system  storage - fat, calcium, phosphorus  heat production - metabolism of brown fat in infants  transport - blood FIBROUS CONNECTIVE TISSUE: CELLS Six cell types  fibroblasts - produce fibers & ground substance of matrix  macrophages - phagocytise foreign material & activate immune system when detecting foreign matter (antigens)  leukocytes, or white blood cells - react against bacteria, toxins & other foreign agents FIBROUS CONNECTIVE TISSUE: CELLS  plasma cells - synthesise antibodies (proteins)  mast cells - often found alongside blood vessels  secrete heparin to inhibit clotting  secrete histamine to dilate blood vessels  adipocytes - store triglycerides (fat molecules) FIBROUS CONNECTIVE TISSUE: FIBRES  Collagenous fibers  collagen is most abundant protein in body - 25%  tough, flexible & stretch-resisant  tendons, ligaments & deep layer of skin are mostly collagen  Reticular fibers  thin collagen fibers coated with glycoprotein - form framework for spleen & lymph nodes  Elastic fibers  thinner than collagenous fibers - branch & rejoin each other  made of protein called elastin - allows stretch & recoil FIBROUS CONNECTIVE TISSUE: GROUND SUBSTANCE/MATRIX  gelatinous to rubbery consistency  Glycosaminoglycans (GAGs)  long polysaccharides comprising amino sugars & uronic acid (disaccharides)  regulate water & electrolyte balance of tissues  Proteoglycans  large molecules (core protein plus GAGs) shaped like bottle brushes  form colloids that hold tissues together  Adhesive glycoproteins  protein-carbohydrate complexes  bind components of tissue together TYPES OF FIBROUS CONNECTIVE TISSUE  Loose connective tissue  abundant gel-like ground substance between cells  Types  areolar  reticular  Dense connective tissue  fibers fill spaces between cells  Types vary in fibre orientation  dense regular connective tissue  dense irregular connective tissue AREOLAR TISSUE  loosely organized fibers, abundant blood vessels - possess all six cell types  mostly collagenous, but also elastic & reticular fibres  found in tissues in almost every part of body [around blood vessels & nerves]  ready supply of infection-fighting leukocytes that move freely in areolar tissue a: © McGraw-Hill Education/Dennis Strete, photographer Figure 5.14a,b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. RETICULAR TISSUE  mesh of reticular fibers & fibroblasts  forms supportive stroma (framework) for lymphatic organs  found in lymph nodes, spleen, thymus & bone marrow a: © McGraw-Hill Education/Al Telser, photographer Figure 5.15a,b DENSE REGULAR CONNECTIVE TISSUE  densely packed, parallel collagen fibers  elastic tissue forms wavy sheets in some locations  tendons & ligaments Figure 5.16a,b a: © McGraw-Hill Education/Dennis Strete, photographer DENSE IRREGULAR CONNECTIVE TISSUE  densely packed, randomly arranged, collagen fibers & few visible cells  withstands unpredictable stresses  locations: deeper layer of skin; capsules around organs a: © McGraw-Hill Education/Dennis Strete, photographer  Figure 5.17a,b ADIPOSE TISSUE  empty-looking cells with thin margins & nucleus pressed against cell membrane  energy storage, insulation, cushioning  subcutaneous fat & organ packing  brown fat of juveniles produces heat a: © McGraw-Hill Education/Dennis Strete, photographer Figure 5.18a,b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. CARTILAGE  firm connective tissue with flexible matrix  types of cartilage vary with fibre composition  hyaline cartilage, fibrocartilage & elastic cartilage  chondroblasts - cartilage cells - produce matrix that surrounds them  chondrocytes – mature cartilage cells  perichondrium - sheath of dense irregular connective tissue that surrounds elastic & most hyaline cartilage (not articular cartilage)  contains reserve population of chondroblasts - cartilage growth  lacks blood vessels - diffusion brings nutrients & removes wastes HYALINE CARTILAGE  clear, glassy appearance - very fine collagen fibers  movement, holds airway open, growth of long bones  locations: articular cartilage, costal cartilage, trachea, larynx, fetal skeleton a: © Ed Reschke Figure 5.19a,b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. ELASTIC CARTILAGE  abundance of elastic fibers  covered with perichondrium  provides flexible, elastic support  external ear & epiglottis Figure 5.20a,b ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. FIBROCARTILAGE  contains large, coarse bundles of collagen fibers  resists compression & absorbs shock  pubic symphysis, menisci & intervertebral discs Figure 5.21a,b a: © Dr. Alvin Telser ©McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education. BONE  connective tissue comprising cells, fibres & ground substance Four principal types of bone cells  Osteogenic cells  Osteoblasts  Osteocytes  Osteoclasts  Osteogenic cells: stem cells arise from embryonic mesenchyme BONE CELLS  multiply continuously & give rise to most other bone cell types  Osteoblasts: bone-forming cells  form single layer under endosteum & periosteum & are non-mitotic  synthesise soft organic matter of matrix - hardens by mineral deposition  stress stimulates osteogenic cells to multiply & increase number of osteoblasts - reinforces bone BONE CELLS  Osteocytes: former osteoblasts - trapped in the matrix they deposited  reside in lacunae - small cavities  lacunae connected by canaliculi  cytoplasmic processes extend into canaliculi & contact processes of other osteocytes  gap junctions allow for passage of nutrients, wastes, signals  act as strain sensors - bone produces biochemical signals that regulate bone remodeling (shape & density changes that are adaptive) BONE CELLS  Osteoclasts: bone-dissolving cells found on bone surface  large cells formed by fusion of several stem cells - multiple nuclei in each cell  ruffled border (large surface area) faces bone  often reside in resorption bays (pits in bone surface)  dissolving bone is part of bone remodeling BONE MATRIX  1/ organic & 2/ inorganic matter 3 3  Organic matter synthesized by osteoblasts  collagen, carbohydrate–protein complexes [glycosaminoglycans, proteoglycans & glycoproteins  Inorganic matter  85% hydroxyapatite (crystallized calcium phosphate salt)  10% calcium carbonate  other minerals (fluoride, sodium, potassium, magnesium) BONE MATRIX  composite material - combination of a ceramic & a polymer  hydroxyapatite & other minerals are the ceramic & collagen (protein) the polymer  ceramic portion allows bone to support body weight without sagging  rickets - caused by mineral deficiency resulting in soft, deformed bones  polymer (protein) gives some flexibility  osteogenesis imperfecta (brittle bone disease) results from defect in collagen deposition TYPES OF BONE TISSUE Figure 7.4a,c,d Copyright © McGraw-Hill Education. Permission required for reproduction or display. a: © B Christopher/Alamy; c: © Biophoto Associates/Science Source; d: © Custom Medical Stock Photo/Newscom COMPACT BONE  periosteum - tough fibrous connective tissue covering the whole bone  bone matrix deposited in concentric lamellae  onion-like layers around central canals  contain osteocytes in lacunae  arranged in cylinders surrounding central (Haversian) canals  run longitudinally through shafts of long bones  blood vessels & nerves travel through central canal  perforating canals - transverse or diagonal passages Figure 7.4b,d a: © B Christopher/Alamy; c: © Biophoto Associates/Science Source; d: © Custom Medical Stock Photo/Newscom COMPACT BONE HIGH MAGNIFICATION Osteon Interstitial lamella Lamella Central canal Photos © McGraw-Hill Education Osteocytes Lacunae Canaliculi Cement line SPONGY BONE  lattice of bone covered with endosteum  slivers of bone called spicules  thin plates of bone called trabeculae  spaces filled with red bone marrow  few osteons & no central canals  all osteocytes close to bone marrow  provides strength with minimal weight  trabeculae develop along lines Photos © McGraw-Hill Education SPONGY BONE STRUCTURE IN RELATION TO MECHANICAL STRESS Figure 7.5 © Biophoto Associates/Science Source Copyright © McGraw-Hill Education. Permission required for reproduction or display. BONE MARROW  soft tissue found in marrow cavities of long bones & small spaces of spongy bone  Red marrow (myeloid tissue)  contains hemopoietic tissue - produces blood cells  in nearly every bone in a child  in adults - skull, vertebrae, ribs, sternum, part of pelvic girdle & heads of humerus & femur  Yellow marrow found in adults  fatty marrow that does not produce blood  can transform back to red marrow in event of chronic anemia LEARNING OUTCOMES By the end of this lecture you should be able to:  Name the four primary classes into which all adult tissues are classified√  Outline the cells, fibres & ground substance of these tissues √  Describe two mechanisms of bone formation  Discuss the hormones involved in calcium metabolism in the body BONE DEVELOPMENT  ossification or osteogenesis - the formation of bone  in human fetus & infant, bone develops by two methods  Intramembranous ossification [within membrane]  produces flat bones of skull & clavicle in fetus  thickens long bones throughout life  Endochondral ossification [within cartilage]  all other bones INTRAMEMBRANOUS OSSIFICATION 1) Deposition of osteoid tissue into 2) Calcification of osteoid tissue and embryonic mesenchyme entrapment of osteocytes 4) Filling of space to form compact 3) Honeycomb of spongy bone with bone at surfaces, leaving spongy bone in middle developing periosteum Figure 7.7 Copyright © McGraw-Hill Education. Permission required for reproduction or display. INTRAMEMBRANOUS OSSIFICATION Figure 7.8 Copyright © McGraw-Hill Education. Permission required for reproduction or display. © Ken Saladin ENDOCHONDRAL OSSIFICATION 1) Early cartilage model 2)Formation of primary centre of ossification, bony collar & periosteum 3)Vascular invasion, formation of primary marrow cavity & appearance of secondary ossification centre 4)Bone at birth, with enlarged primary marrow cavity and appearance of secondary marrow cavity in one epiphysis 5)Bone of child, with epiphyseal plate at distal end Figure 7.9 Copyright © McGraw-Hill Education. Permission required for reproduction or display. 6)Adult bone with a single marrow cavity & closed epiphyseal plate THE FETAL SKELETON AT 12 WEEKS © Biophoto Associates/Science Source Figure 7.10 Copyright © McGraw-Hill Education. Permission required for reproduction or display. BONE REMODELING  absorption & deposition  occurs throughout life - 10% of skeleton per year  repairs microfractures, releases minerals into blood, reshapes bones in response to use & disuse  Wolff’s law of bone: architecture of bone determined by mechanical stresses placed on it  remodeling is collaborative & precise action of osteoblasts & osteoclasts  bony processes grow larger in response to mechanical stress BONE PHYSIOLOGY  mature bone a metabolically active organ  involved in own maintenance of growth & remodeling  exerts influence over rest of body by exchanging minerals with tissue fluid  disturbance of calcium homeostasis in skeleton disrupts function of other organ systems  especially nervous & muscle tissue LEARNING OUTCOMES By the end of this lecture you should be able to:  Name the four primary classes into which all adult tissues are classified √  Outline the cells, fibres & ground substance of these tissues √  Describe two mechanisms of bone formation √  Discuss the hormones involved in calcium metabolism in the body MINERAL DEPOSITION & RESORPTION  mineral deposition (mineralisation) – Ca+, phosphate & other ions are taken from blood & deposited in bone  osteoblasts produce collagen fibers that spiral the length of the osteon  fibres become encrusted with minerals  hydroxyapatite crystals  first few crystals act as seed crystals that attract more Ca+ & phosphate from solution  abnormal calcification (ectopic ossification) - formation of a calculus (calcified mass) in otherwise soft organ [lung, brain, eye, muscle, tendon or artery (arteriosclerosis)] MINERAL DEPOSITION & RESORPTION  process of dissolving bone & releasing minerals into blood performed by osteoclasts at ruffled border  H- pumps in membranes secrete H- into space between osteoclast & bone surface  Cl- ions follow by electrical attraction  hydrochloric acid (pH 4) dissolves bone minerals  acid protease enzyme digests collagen CALCIUM HOMEOSTASIS  Ca+ & PO3-4 used for more than bone structure  PO3-4 is component of DNA, RNA, ATP, phospholipids, and pH buffers  Ca+ needed in neuronal communication, muscle contraction, blood clotting  minerals deposited in skeleton & withdrawn when needed for other purposes CALCIUM HOMEOSTASIS  ± 1,100 g Ca+ in adult body - 99% in bones  most exists in hydroxyapatite, but some in form easily exchanged with blood  18% of skeletal Ca+ is exchanged with blood each year  Normal Ca+ concentration in blood plasma is 9.2-10.4 mg/dL  45% as that can diffuse across capillary walls & affect other tissues  rest in reserve, bound to plasma proteins CALCIUM HOMEOSTASIS  Hypocalcemia – deficiency in Ca+ in blood  changes membrane potentials & causes overly excitable nervous system & tetany (muscle spasms)  Vitamin D deficiency, diarrhoea, thyroid tumors, underactive parathyroid glands  pregnancy & lactation increase risk of hypocalcemia  Hypercalcemia - excessive Ca+ levels  makes ion channels less responsive & thus nerve & muscle are less excitable  can cause muscle weakness, slow reflexes, cardiac arrest CALCIUM HOMEOSTASIS  depends on balance between dietary intake, urinary & faecal losses, & exchanges between osseous tissue  regulated by three hormones:  Calcitriol  Calcitonin  Parathyroid hormone CALCITRIOL      most active form of vitamin D skin uses UV radiation to produce liver converts D3 to calcidiol kidney converts that to calcitriol raises blood Ca+ level – essential for bone deposition  increases Ca+ absorption by small intestine & Ca+ resorption from skeleton  stimulates osteoblasts to release chemical that stimulates production of osteoclasts  weak promoter of kidney reabsorption of Ca+ ions – fewer lost Figure 7.14 in urine Copyright © McGraw-Hill Education. Permission required for reproduction or display. CALCITONIN  secreted by cells of thyroid gland when blood Ca+ levels rise too high  lowers blood Ca+ concentration in two ways:  inhibits osteoclasts thereby reducing bone resorption  stimulates osteoblasts to deposit calcium into bone  important in children, weak effect in adults  osteoclasts more active in children due to faster remodeling  may inhibit bone loss in pregnant & lactating women Parathyroid Hormone  from parathyroid glands [on posterior surface of thyroid gland]  released when blood Ca+ levels low  raises Ca+ blood level by four mechanisms  stimulates osteoblasts to secrete RANKL - increases osteoclast population & bone resorption  promotes Ca+ reabsorption by kidneys - less lost in urine  promotes final step of calcitriol synthesis in kidneys, enhancing calcium-raising effect of calcitriol  inhibits collagen synthesis by osteoblasts, inhibiting bone deposition NEGATIVE FEEDBACK LOOPS IN CALCIUM HOMEOSTASIS (a) Correction for hypercalcemia Figure 7.16a Copyright © McGraw-Hill Education. Permission required for reproduction or display. NEGATIVE FEEDBACK LOOPS IN CALCIUM HOMEOSTASIS (b) Correction for hypocalcemia Copyright © McGraw-Hill Education. Permission required for reproduction or display. Figure 7.16b LEARNING OUTCOMES By the end of this lecture you should be able to:  Name the four primary classes into which all adult tissues are classified √  Outline the cells, fibres & ground substance of these tissues √  Describe two mechanisms of bone formation √  Discuss the hormones involved in calcium metabolism in the body √ NEXT LECTURE MUSCULOSKELETAL SYSTEM 1