Tissue The Living Fabric Chapter 4 4 Types

Tissue: The Living Fabric Chapter 4

4 Types of Tissues Epithelial (covering) n Connective (support) n Muscle (movement) n Nervous (control) Histology - study of tissues n

I. Epithelial Tissue p. 99 n Sheet of cells that covers a body surface or lines a body cavity 1. Covering & lining epithelium 2. Glandular epithelium

A. Special Characteristics 1. 2. 3. 4. 5. 6. Cellularity Specialized Contacts Polarity (apical & basal surfaces) microvilli, cilia, basal lamina Supported by Connective Tissue reticular lamina, basement membrane Avascular, but Innervated Regeneration

B. Classification 2 Names: 1 st Name - How many layers of cells. 2 nd Name - Shape of cells. n Simple vs. Stratified n Squamous vs. cuboidal vs. columnar n Nucleus shape conforms to cell. n Look at fig. 4. 1 p. 100 n

1. Simple Epithelia p. 101 Most concerned with absorption, secretion, and filtration. n Simple Squamous Epithelium n n Thin and permeable - filtration or exchange of substances by rapid diffusion n Found in places like the kidney filtration membrane, lung air sacs, capillaries, serous membranes n Simple Cuboidal Epithelium n Secretion and absorption n Common in kidney tubules and glands

n Simple Columnar Epithelium n Absorption and secretion n Lines digestive tract n n Dense microvilli Goblet cells - secrete mucus Sometimes cilia Pseudostratified Columnar Epithelium n Vary in height, so it appears that there is more than one layer n Secretion and absorption - ciliated version containing goblet cells lines respiratory tract Fig. 4. 2 p. 101 -103

2. Stratified Epithelia p. 105 2 or more layers, regenerate from below n More durable than simple epithelia Protection n Stratified Squamous Epithelium n n Most widespread, thick n Free surface cells are squamous, deeper are cuboidal or columnar, constant regeneration n External part of skin - keratinized n Stratified Columnar Epithelium n Rare, large ducts of some glands

n Transitional Epithelium n. Lining of urinary organs, subjected to stretching when filled with urine n. Cells change shape when stretched Fig. 4. 2 p. 104 -105

3. Glandular Epithelia p. 106 n n n Gland - one or more cells that make & secrete (export) a particular product (secretion) Secretion is aqueous & usually contains proteins Classified based on: 1. 2. Endocrine or Exocrine Unicellular or Multicellular

a. Endocrine Glands Release their product into the extracellular space n Often ductless n Produce hormones - targeted to specific organ(s) n Most are compact multicellular organs, but some are individual cells (diffuse endocrine system) n We will deal more with this in Chp. 15 n

b. Exocrine Glands More numerous than endocrine glands n Secrete onto body surfaces (skin) or into body cavities n Single or multicelled n Examples: mucous, sweat, oil, salivary, liver, pancreas n Unicellular - goblet cell - produce mucin (becomes mucus) n

b. Exocrine Glands cont’d n Multicellular n 2 parts: duct & secretory unit n Supportive connective tissue surrounds the secretory unit, often forming a fibrous capsule that extends into the gland, dividing it into lobes n Simple or Compound n n Simple - single unbranched duct Compound - branched duct n Also n n n categorized by secretory units: Tubular - form tubes Alveolar (acinar) - form small sacs Tubuloalveolar - contain both

Multicellular cont’d n Different modes of secretion: n Merocrine glands - secrete products by exocytosis examples: pancreas, most sweat glands, & salivary glands n Holocrine glands - accumulate products within the cells until they rupture - cells are replaced by division of lower cells - example: sebaceous (oil) glands of the skin Fig. 4. 4&4. 5, p. 107 -108

II. Connective Tissue p. 108 Most abundant and widely distributed of the primary tissues n 4 main classes: (fig. 4. 6 p. 109) n n n Connective tissue proper, cartilage, bone, and blood 4 major functions: n Binding & support, protection, insulation, and transportation

A. Common Characteristics 1. 2. 3. 4. Common origin - from mesenchyme Degrees of vascularity - wide range Extracellular matrix - mostly composed of this matrix, few cells --> This allows it to withstand a lot of physical stress and abuse

B. Structural Elements p. 109 n 3 main elements: Ground substance n Fibers n Cells n Ground substance and fibers make up the extracellular matrix n Wide variety within connective tissues, but areolar connective tissue is used as a prototype or model (fig. 4. 7 p. 110) n

1. Ground Substance p. 109 Unstructured material that fills the space between cells, contains fibers n Composed of interstitial fluid, cell adhesion proteins, and proteoglycans n Holds large amounts of fluid n Functions as a molecular sieve, or medium, through which nutrients and other dissolved substances can diffuse between the capillaries and the cells n

2. Fibers p. 110 n n Provide support 3 Types: n n n Collagen Fibers: made of collagen protein, very tough (stronger than steel), thick, white fibers Elastic Fibers: made of elastin protein, long & thin, rebound tissue when stretched, yellow fibers, found in skin, lungs, blood vessels Reticular Fibers: made of collagen protein, thin, form delicate networks, found in small blood vessels & basement membrane of epithelial tissues

3. Cells p. 111 n Each class has its own fundamental cell type: -blast indicates undifferentiated cells Fibroblast - connective tissue proper 2. Chondroblast - cartilage 3. Osteoblast - bone 4. Hematopoietic stem cell - blood Once these cells synthesize the matrix, they become mature, -cyte is added to name 1.

3. Cells cont’d Accessory cells: fat cells, white blood cells, mast cells, macrophages, plasma cells n Mast cells: cluster along blood vessels, detect foreign substances & initiate inflammatory response (release histamine) n Macrophages: phagocytize foreign materials & dead tissue cells, part of immune system n

C. Types of Connective Tissue p. 112 -119 Embryonic connective tissue: Mesenchyme 1. - first definitive tissue formed Arises during the early weeks of embryonic development and eventually differentiates into all other connective tissues

2. Connective tissue proper Loose connective tissue, p. 111 a) § § § Areolar connective tissue - “universal packing material between other tissues, ” has all 3 fiber types Adipose (fat) tissue - similar to areolar but has greater nutrient-storing ability, cells are adipocytes Reticular connective tissue - only reticular fibers, lymph nodes, spleen, bone marrow

Dense Connective Tissue b) § Dense regular connective tissue - variety of dense tissues, mostly made up of fibers, also called fibrous connective tissues, poorly vascularized, forms tendons, ligaments § § Some have more elastic fibers (ex. Ligaments of vertebrae) and are called elastic connective tissue Dense irregular connective tissue - similar to last type, but collagen fibers are thicker and are arranged irregularly, found in dermis, joint capsules

3. Cartilage p. 116 n n Stands up to both tension and compression, characteristics intermediate between dense connective tissue and bone Avascular and lacks nerve fibers Contains up to 80% water, Chondrocytes are the primary cell 3 types of cartilage: 1. Hyaline: most abundant, lots of collagen, examples: articular cartilage, tip of nose, connect ribs to sternum, respiratory system passages, embryonic skeleton, epiphyseal plates

3 types of Cartilage con’t 2. 3. Elastic Cartilage: similar to hyaline, but with more elastin fibers, examples: external ear, epiglottis Fibrocartilage: often found where hyaline meets a true ligament or tendon, examples: intervertebral discs, menisci of knee

4. Bone p. 118 Also known as osseous tissue n Supports and protects body tissues, stores fat, and synthesizes blood cells n Matrix is similar to cartilage but harder, because of inorganic calcium salts n Well supplied by blood vessels n More on bone in ch. 6 n

5. Blood p. 118 Does not connect things or give support n But it does come from mesenchyme and has blood cells surrounded by a fluid matrix (blood plasma) n The fibers of blood are only visible during clotting n Transport system in the body n We will deal more with blood in ch. 16 n

III. Epithelial Membranes: Coverings and Linings p. 118 Incorporate both epithelial and connective tissues n “A continuous multicellular sheet composed of at least 2 primary tissue types: an epithelium bound to an underlying layer of connective tissue proper, ” so they are simple organs n 3 types: cutaneous, mucous, & serous n Fig. 4. 9 p. 120 n

A. Cutaneous Membrane p. 120 Skin, consists of keratinized stratified squamous epithelium (epidermis) attached to a thick layer of dense irregular connective tissue (dermis) n Dry membrane (exposed to air) n Ch. 5 for more with this organ system n

B. Mucous Membrane p. 121 Line body cavities that open to the exterior - i. e. digestive, respiratory, & urogenital tracts n Wet membranes n Most have stratified squamous or simple columnar epithelia over a layer of loose connective tissue, which sometimes lays on a third layer of smooth muscle cells n Often for absorption and secretion n

C. Serous Membrane p. 121 n n Wet membranes found in closed ventral body cavities Consists of simple squamous epithelium (mesothelium) resting on a thin layer of loose connective (areolar) tissue Has serous fluid that lubricates moving organs Named for the organs they surround: pleura = lungs; pericardium = heart; peritoneums = organs of abdominopelvic cavity

IV. Nervous Tissue p. 121 Main parts of nervous system – brain, spinal cord, and nerves n 2 major cell types: n Neurons - generate and conduct nerve impulses n Supporting cells - support, insulate, and protect the neurons n Fig. 4. 10 p. 121 More in Ch. 11 n

V. Muscle Tissue p. 122 Highly cellular, well-vascularized, responsible for movement n Myofilaments: actin and myosin protein fibers that are responsible for contraction 3 Types: A. Skeletal - attached to bones, muscle fibers (cells) are long with many nuclei, striated, voluntary (chp. 9) n

V. Muscle Tissue con’t B. Cardiac - found only in heart, pumps blood, striated, uninucleate, involuntary, branching cells that connect at intercalated discs (an area with a lot of gap junctions), ch. 17 Smooth - no striations, spindle shaped uninucleate cells, found in hollow organs (ex. Digestive, urinary, uterus, blood vessels), involuntary ch. 9 Fig. 4. 11, p. 122 -123

VI. Tissue Repair p. 122 The body has several defense mechanisms for preventing injury and infection - when these are penetrated, the inflammatory and immune responses are triggered to get rid of infection. n The tissue then must be repaired. n

A. Steps, p. 124 n Occurs in 2 major ways, which depend on the type of tissue damaged and the severity of the injury n n Regeneration - replacement of tissue with the same kind of tissue Fibrosis - replacement of tissue with fibrous connective tissue (scar tissue) Step 1: Inflammation sets the stage. Step 2: Organization restores the blood supply. Step 3: Regeneration and fibrosis effect permanent repair.

B. Homeostatic Imbalance p. 125 During the healing process, tissues which cannot regenerate very well produce a large amount of scar tissue, which is not as flexible as the original tissue. n It also causes some shrinking in the tissue. This can be serious in organs like the heart, where it reduces capacity and function. Internal organs can also get stuck together during healing, causing dysfunction & pain. n