Unit 2: Tissues

  1. What is a Tissue?
    a group of cells with similar origin and function
  2. What are the four major types of tissues and what do they do?
    Epithelial tissues: cover surfaces, line cavities, form secretory parts of glands 

    Connective tissues: connect other tissues, support, protect, transport (blood), insulate (fat)

    Muscle tissues: movement

    Nervous tissue: recognizing and responding to stimuli (changes in environment), transfer information
  3. Embryonic Tissue is formed by what?
    by embryonic stem cells that arise 13-14 days after fertilization
  4. What are the 3 layers that Embryonic stem cells that form?
    Ectoderm (outer) – forms skin and nervous system 

    Mesoderm (middle) – forms muscle, bone and blood vessels

    Endoderm (inner) – forms lining of digestive tract and derivatives
  5. Epithelial Tissue: Features?
    •Closely packed cells (cell junctions) 

    •Little extracellular matrix

    •Single (simple) or multi-layered (stratified)

    •Associated with underlying connective tissue

    •Avascular (no blood vessels)

    •Regeneration (mitotic cell division)

  6. Epithelial Tissue: Polarity
    •Apical surface - free edge exposed to body exterior or cavity 

    • •Basal surface - attached to basement membrane
    • --specialized type of extra- cellular material secreted by epithelial & connective cells 
    • --important to tissue repair
  7. Classification of Epithelial Tissue:

    See Table: 4.1 p.113
    • Number of layers:      Shape of cells:
    • Simple                           Squamous
    • Stratified                       Cuboidal 
    •                                     Columnar
  8. Types of Epithelial Tissue:
    • Simple Tissue 
    • Simple Squamous*
    • Simple Cuboidal*
    • Simple Columnar*
    • Pseudostratified Columnar*

    • Stratified Tissue
    • *Defined by the shape of the outer cells

    • Stratified Squamous*
    • Stratified Columnar
    • Stratified Cuboidal
    • Transitional*
  9. Simple Squamous Epithelium

    *Table 4.2a
    Function: filtration, diffusion, secretion, protection 

    • Location:
    • •endothelium (lining of blood and lymphatic vessels, heart)
    • •mesothelium (serous membranes of ventral body cavity)
    • •kidneys, lungs
  10. Simple Cuboidal Epithelium:

    *Table 4.2b
    • Function
    • •secretion 
    • •absorption 

    • Location:
    • •kidneys 
    • •glands
  11. Simple Columnar Epithelium: 

    *Table 4.2 c
    • Function
    • •secretion 
    • •absorption 

    • Location:
    • •digestive, respiratory & reproductive systems 

    • Modifications:
    • •Cilia - movement of materials; e.g., uterine tubes 
    • •Microvilli - increase surface area for absorption; small intestine 
    • •Goblet cells - secrete mucous for lubrication; GI
  12. Pseudostratified Columnar Epithelium

    *Table 4.4a
    • •false (pseudo) layers 
    • •nuclei at different levels give appearance of being multilayered 
    • •all cells rest on basement membrane but NOT all reach free surface 

    Function: secretion

    Location: respiratory system

    • Modifications:
    • –cilia - respiratory system 
    • –goblet cells - respiratory system
  13. Stratified Squamous Epithelium

    *Table 4.3a
    • Function:
    • •protection against abrasion

    • Location:
    • •Keratinized (epidermis of skin)
    • –contains keratin (water-proof protein)

    • •Non-keratinized (mouth, esophagus, vagina, anus)
    • –lacks keratin
  14. Stratified Cuboidal Epithelium

    *Table 4.3b
    • Function: 
    • •protection
    • •absorption
    • •secretion

    • Location:
    • •ducts of sweat & salivary glands
  15. Stratified Columnar Epithelium

    *Table 4.3c
    • Function: 
    • •protection 
    • •secretion 

    • Location:
    • •male urethra
    • •mammary gland ducts
  16. Transitional Epithelium

    *Table 4.4b
    • •Stretched - uppermost cells are squamous 
    • •Relaxed - uppermost cells are cuboidal 

    • Function:
    • •capable of  stretching to accommodate fluctuations in fluid volume

    • Location:
    • –urinary system
  17. Cell Connections
    • Tight junctions - tight seals between cells 
    • •prevent movement of substances
    • •stomach & urinary bladder

    • Desmosomes - disc-shaped structures
    • •resist stretching & twisting 
    • •skin epidermis, heart 

    • Gap junctions - protein channels 
    • •allow transfer of ions à electric signaling between cells 
    • •cardiac & smooth muscle tissue
  18. Simple columnar epithelium of the digestive tract is characterized by:
    • a)fibroblasts 
    • b)a rich vascular supply
    • c)cilia
    • d)dense microvilli
  19. Simple cuboidal epithelia are usually associated with secretion and absorption.
  20. Glands
    •Composed primarily of epithelium with supporting network of connective tissue 

    Endocrine glands secrete hormones into blood (by way of interstitial fluid)

    • •e.g., pituitary gland, adrenal gland, pancreas
    • *will be covered in Unit XI & XII
  21. Glands

    *Figure 4.4
    • Exocrine glands secrete products into ducts 
    • •classified by shape & complexity 
    • •classified by mode of secretion

    • merocrine glands - secrete product; sweat glands
    • apocrine glands – secrete product + fragments of cells; mammary glands
    • holocrine glands – product + entire cell; oil glands
  22. Connective Tissue (CT):  Features
    • •well-innervated 
    • •highly vascular (except cartilage) 
    • •few cells embedded in large amount of extracellular (outside the cell) matrix 
    • •structural elements: matrix and cells 
    • –each type of CT has its own associated cell type & matrix
    • •all CT arise from mesenchymal cells
  23. CT: Structural Elements - Matrix

    *Figure 4.5
    = consists of ground substance, fibers and fluid 

    • Ground substance
    • •shapeless
    • •contains nonfibrous proteins (hyaluronic acid and proteoglycans) 
    • •consistency varies from rock-hard (bone) to watery fluid (plasma)
  24. CT: Matrix - Fibers (Proteins)

    *Figure 4.5
    • Collagen 
    • –thick, most abundant fibers
    • –Strong, resists pulling tension

    • Reticular
    • –fine strands of collagen
    • –form network around blood vessels, soft organs, basement membrane

    • Elastic (elastin)
    • –stretch and recoil without breakage
    • –skin, lungs, blood vessels
  25. Connective Tissue: Cells
    Blasts – create matrix (mitotically active) 

    • What does it mean?
    • –e.g., fibroblasts, osteoblasts

    • Cytes – maintain matrix (mature cell)
    • –e.g., adipocytes, osteocytes

    • Clasts – break down (reabsorb) matrix
    • –e.g., osteoclasts
  26. Types of Connective Tissue

    *Table 4.6
    • Embryonic CT 
    • Mesenchyme (irregularly shaped osteoblasts & semifluid matix)
    • Mucous (support umbilical cord blood vessels)

    • Adult CT
    • Connective tissue proper – Loose and Dense
    • Supporting CT – Cartilage and Bone
    • Fluid CT – Blood and Hematopoietic tissue
  27. Review: CT Proper: Loose CT
    •areolar, adipose and reticular 

    • Areolar *Table 4.8
    • •contains three types of fibers
    • •cells: fibroblasts, macrophages, mast cells

    • What is the function of each cell type?
    • •water and solute reservoir
    • •associated with most epithelial membranes
    • –forms lamina propria of mucous membranes
    • –forms papillary layer of dermis
  28. Review: Loose CT - Adipose

    *Table 4.8
    • •adipocytes, fibers & small extracellular matrix 
    • •insulates, stores energy, absorbs shock
    • •subcutaneous areas & around organs
    • •liposuction
  29. Loose CT - Reticular

    *Table 4.8
    • •network of reticular fibers irregularly arranged 
    • •cells – dendritic (immune) cells, microphages
    • •forms framework of spleen, liver, lymph nodes, bone marrow
  30. CT Proper: Dense CT
    • Dense Regular 
    • –Collagenous
    • –Elastic

    • Dense Irregular
    • –Collagenous
    • –Elastic
  31. Review: Dense Regular Collagenous
    •densely packed parallel collagen fibers 

    function: provides strength & resists tension in one direction

    location: tendons (muscle-bone); ligaments (bone-bone), aponeuroses (wide tendons)
  32. Dense Regular Elastic

    *Table 4.9b
    • •abundant elastic fibers (elastin=yellow color) 
    • •parallel bundles of collagen fibers

    function: stretch and recoil

    location: elastic ligaments of vocal folds and between vertebrae
  33. Dense Irregular CT
    • •randomly oriented fibers 
    • •withstand stretching in all directions

    • Dense Irregular Collagenous
    • •collagen fibers - provide strength
    • •dermis 
    • •fibrous capsules around some organs, e.g., kidneys, testes, heart (fibrous pericardium) 
    • •perichondrium, periosteum
  34. As we age…
    •Tissues change (as a result of changing cells) affects organ function and structure that decrease: 

    • –Lung capacity by 50%
    • –Muscle strength by 45% 
    • –Kidneys by 30% 


    •Collagen & elastin decrease --> tissue stiffer, less elastic --> less efficient

    • •Fat content changes
    • –Male – increases until age 60, then gradually decreases
    • –Female – fat accumulates continuously

    •Total amount of water decreases --> slower metabolism --> slower response to drugs

    •Tissue atrophy --> decrease in mass of most organs

    Would it affect function of the organ?
  35. Supporting CT: Cartilage
    • •avascular 
    • •perichondrium = dense irregular CT surrounding cartilage (supplies blood)
    • •lack innervation
    • •cells = chondroblasts (during cartilage formation) and chondrocytes (mature) found in lacunae (lacuna) 

    • •types:
    • Hyaline Cartilage 
    • Elastic Cartilage 
    • Fibrocartilage 
  36. Review: Hyaline Cartilage

    *Table 4.10a
    • •most abundant 
    • •collagen fibers (not visible) make it strong, yet pliable 
    • •tip of nose, respiratory system, epiphyseal plate (growing bone), fetal skeleton, articular cartilage, ribs 

    Which part of a bone is covered with the articular cartilage?  Explain why.
  37. Review: Fibrocartilage

    *Table 4.10b
    • •thick bundles of collagen fibers 
    • •compressible and tough
    • •intervertebral disks, menisci (knee), symphysis pubis
  38. Review: Elastic Cartilage

    *Table 4.10c
    • •elastic fibers 
    • •provides rigidity and flexibility
    • •allow recoil after bending
    • •external ear (pinna), epiglottis and auditory tubes
  39. Review: Supporting CT: Bone
    • Functions
    • •forms the skeletal system
    • •provides support,
    • •movement (muscle attachment),
    • •protection,
    • •hemopoiesis ( hematopoiesis)= blood cell formation

    • Features:
    • •osteocytes in hard matrix (calcium, magnesium and phosphate salts);
    • •collagen fibers and other proteins
  40. Review: Types of Bone

    *Table 4.11a
    • Cancellous (spongy) bone 
    • –plates of bone called trabeculae
    • –spaces between trabeculae are filled with bone marrow and blood vessels
    • –found in interior of bones of the skull, vertebrae, sternum, pelvis, and ends of long bones.

    • Compact bone
    • –based on osteon (haversian system)
    • –outer portion of all bones and shafts of long bones
  41. Review: Fluid CT: Blood

    *Table 4.12a
    • •cells & cell fragments (suspended in matrix-plasma) 
    • leukocytes = white blood cells (WBCs)
    • erythrocytes = red blood cells (RBCs) 
    • platelets (cell fragments) 

    •contains solutes (ions, nutrients, wastes) and suspended substances, e.g., large proteins

    • Functions
    • •fights diseases 
    • •transports substances, 
    • e.g., nutrients, wastes, hormones, respiratory gasses
  42. Fluid CT: Hematopoietic Tissue

    *Table 4.12b
    • Function & location
    • –forms blood cells (red bone marrow)
    • –stores lipids (yellow bone marrow)
  43. Review: Muscle Tissue

    *Table 4.13
    • •high  metabolic rate 
    • •highly vascular (needs good supply of oxygen & nutrients when active) 
    • •produce movement of body parts including movement of materials through tubes 
    • cells = muscle fibers 

    • •types:
    • Skeletal
    • Cardiac
    • Smooth
  44. Review: Muscle Tissue: Skeletal

    *Table 4.14a
    • Location - attached to bones 
    • Function - voluntary movement of skeleton & control of sphincters  
    • Cells 
    • –large, long, cylindrical & striated
    • multinucleate (develops from union of cells)
  45. Review: Muscle Tissues: Cardiac

    *Table 4.14b
    • Location - myocardium (heart) 
    • Function –pumps blood through the body
    • Cells
    • – striated,  involuntary, branching
    • uninucleate
    • Intercalated disks (cell to cell junctions) allow rapid spread of impulses from one cell to another
  46. Review: Muscle Tissues: Smooth

    *Table 4.14c
    Location - walls of hollow organs 

    • Function:
    • –regulates size of organs
    • –forces substances through tubes

    • Cells
    • –tapered ends, no visible striations
    • –involuntary
    • –uninucleate
  47. Review: Nervous Tissue
    • Functions
    • recognize environmental changes 
    • integrates sensory inputs and motor outputs 
    • controls motor outputs (muscle contraction, glandular secretion) 
  48. Review: Nervous Tissue: 
    Structural Components

    *Figure 4.6
    • Neurons 
    • •conduct information (sensation, motor impulses)

    • •Neuroglia
    • protect, insulate, support neurons
  49. The presence of lacunae, calcium salts, and blood vessels would indicate:
    • a.Cartilage tissue 
    • b.Fibrocartilage tissue
    • c.Osseous tissue
    • d.Areolar tissue
  50. Most connective tissues have regenerative capacity while most epithelial tissues do not. 
    (TRUE/ FALSE) 
  51. Epithelial Membranes
    • Consist of
    • epithelial tissue and 
    • connective tissue (CT) 

    • Three types:
    • Cutaneous Membrane (“dry” membrane)
    • Mucous Membranes (“wet” membranes)
    • Serous Membranes (“wet” membranes)
  52. Cutaneous Membrane

    *Figure 4.7
    •forms skin

    • consists of:
    • keratinized stratified squamous epithelium (epidermis)

    • connective tissue (dermis)
    • •areolar CT forms papillary layer, and
    • •dense irregular CT forms reticular layer
  53. Mucous Membranes

    *Figure 4.7
    •line body cavities open to the outside (digestive, respiratory, reproductive, and urinary tracts) 

    non-keratinized stratified squamous epithelium or stratified columnar, or simple columnar

    • •protect, absorb, secrete
    • –some contain goblet cells or mucous glands (mucus)
  54. Serous Membranes

    *Figure 4.7
    • •Line cavities not open to the exterior (except pelvic cavity) 
    • parietal layer - lines wall of cavity 
    • visceral layer - overlies organs

    •Secrete serous fluid (lubricates to prevent friction)

    • Consist of:
    • –simple squamous epithelium (mesothelium) 
    • –areolar CT
  55. Serous Membranes: Location
    • Ventral body cavities and organs: 
    • pericardium - surrounds and covers heart
    • pleura - covers lungs and lines thoracic cavity
    • peritoneum - abdominal cavity and organs

    Inflammation of serosa due to irritation and/or disease

    • pleurisy - in pleural cavity
    • peritonitis - in abdominal cavity 
    • pericarditis - in pericardium

    •The serous membrane that lines the peritoneal cavity is called __________.
  56. Synovial Membrane

    *Figure 4.7
    • •modified connective tissue 
    • •covers all internal joint surfaces that are not covered by hyaline cartilage
    • •produces fluid rich in hyaluronic acid (facilitate smooth movement within joints)
  57. Tissue Repair

    *Table 4.9
    Epithelial tissues usually repair/regenerate well 

    Connective tissues are often replaced by fibrous connective tissue (fibrosis=scar tissue)

    • Events of tissue repair, e.g., skin repair
    • •inflammation (WBC, clotting proteins, fluid)
    • •blood clot formation
    • •new epidermis is formed– epithelium grows into wound
    • •granulation tissue is formed – fibroblasts proliferate
    • •granulation tissue is replaced with dermis
  58. Let’s apply

    Why tendon tears or breaks are difficult to repair both physiologically and surgically?

    What is a scar? 
    • Answer 1
    • •Composed of dense regular connective tissue
    • •Few cells and vascular supply is poor

    • Answer 2:
    • •Occurs when wounds are very deep and cannot close

    Connective tissue fills in the space before epithelial tissue can cover it
Card Set
Unit 2: Tissues