Chapter 4 - Tissue: The Living Fabric
TISSUE DESCRIPTION
- Histology - study of
- Groups of cells similar in structure and function.
- Separated by Extracellular Fluid (ECF) (interstitial fluid)
- Four major types
- Epithelial - lining and covering
- Connective - support; padding; energy storage; etc.)
- Muscular - contractile for movment
- Nervous - responds to environment and conducts impulses
BODY FLUIDS
- For the body's cells to survive, the composition of the surrounding fluids must be precisely maintained at all times.
- Fluid inside body cells is called intracellular fluid.
- Fluid outside body cells is called extracellular fluid (ECF) and is found in two principal places.
- ECF filling the narrow spaces between cells of tissues is called interstitial fluid, intercellular fluid, or tissue fluid.
- ECF in blood vessels is termed plasma.
- Since ECF is in constant motion throughout the body and also surrounds all body cells, it is often called the body's internal environment.
EPITHELIAL TISSUES
- General Characteristics
- Always have a free surface
- cover organs and the body
- line body cavities
- line hollow organs
- Cellularity - composed almost entirely of cells
- Special contacts - form continuous sheets held together by tight junctions and desmosomes
- Polarity - apical (free surface) and basal (basement membrane)
surfaces
- Supported by connective tissue - reticular and basal laminae
- Avascular but innervated - contains no blood vessels but supplied by nerve fibers
- Regenerative - rapidly replaces lost cells by cell division
- Basement membrane opposite the free surface
- Basal lamina
- from epithelial cells
- collagen fibers
- Reticular lamina
- secreted by connective tissue cells
- reticular fibers
- Functions:
- guide for cell migration during development
- may become thickened due to increased collagen and laminin production
- Example: In diabetes mellitus, the basement membrane of small blood vessels, especially those in the retina and kidney, thickens.
- Classification of Epithelial Tissue - based on shape of cell and number of cell layers.
- Simple squamous Epithelial
- Single layer of flattened cells with disc-shaped nuclei and sparse cytoplasm
- Functions
- Diffusion and filtration
- Provide a slick, friction-reducing lining in lymphatic & cardiovascular systems
- Present in kidney glomeruli, endothelium, lymphatic vessels, and serosae
- Simple cuboidal Epithelial
- Single layer of cubelike cells with large, spherical central nuclei
- Function in secretion and absorption
- Present in kidney tubules, ducts and secretory portions of small glands, and ovary surface
- Simple columnar Epithelial
- Single layer of tall cells with oval nuclei; many contain cilia
- Goblet cells are often found in this layer
- Function in absorption and secretion
- Nonciliated type with microvilli line digestive tract and gallbladder
- Ciliated type line small bronchi, uterine tubes, and some regions of the uterus
- Pseudostratified Columnar Epithelial
- Single layer of cells with different heights; some do not reach the free surface
- Nuclei are seen at different layers
- Function in secretion and propulsion of mucus
- Present in the male sperm-carrying ducts (nonciliated) and trachea (ciliated)
- Stratified Squamous Epithelial
- Thick membrane composed of several layers of cells
- Function in protection of underlying areas subjected to abrasion
- Forms the external part of the skin's epidermis (keratinized cells), and linings of the esophagus, mouth, and vagina (nonkeratinized cells)
- Papanicolaou Smear (Pap smear)
- Collect sloughed off cells of uterus and vaginal walls
- Detect cellular changes (precancerous cells)
- Recommended annually for women over 18 or if sexually active
- Stratified Cuboidal and Stratified Columnar
- Stratified cuboidal
- Quite rare in the body
- Found in some sweat and mammary glands
- Typically two cell layers thick
- Stratified columnar
- Limited distribution in the body
- Found in the pharynx, male urethra, and lining some glandular ducts
- Also occurs at transition areas between two other types of epithelia
- Transitional Epithelial
- Several cell layers, basal cells are cuboidal, surface cells are dome shaped
- Stretches to permit the distension of the urinary bladder
- Lines the urinary bladder, ureters, and part of the urethra
- Glandular Epithelium
- Endocrine - secrete directly into body fluids or blood; ductless
- Exocrine - Secrete their products onto body surfaces (skin) or into body cavities
- Examples include mucous, sweat, oil, and salivary glands
- The only important unicellular gland is the goblet cell
- Multicellular exocrine glands are composed of a duct and secretory unit
- Classified by arrangement of cells - simple, compound, tubular , alveolar
- Also classified by secretion method
- merocrine
- apocrine
- holocrine
- Epithelial Membranes - Cutaneous, Mucous, Serous
CONNECTIVE TISSUES
- Found throughout the body; most abundant and widely distributed in primary tissues
- Connective tissue proper
- Cartilage
- Bone
- Blood
- Functions of
- Binding and support
- Protection
- Insulation
- Transportation
- Connective tissues have:
- Mesenchyme as their common tissue of origin
- Varying degrees of vascularity
- Nonliving extracellular matrix, consisting of ground substance and fibers
- Extracellular Matrix and Cells
- Ground substance - fills the space between cells (Interstitial fluid)
- Adhesion proteins - fibronectin and laminin
- Proteoglycans - glycosaminoglycans (GAGs)
- hyaluronic acid is thick, viscous and slippery
- chondroitin sulfate is jellylike substance providing support
- Chondroitin sulfate and glucosamine are used as nutritional supplements to maintain joint cartilage. It is not known why the supplements benefit some individuals and not others.
- Functions as a molecular sieve through which nutrients diffuse between blood capillaries and cells
- Fibers
- Collagen fibers - tough and resistant to stretching
- allow some flexibility in tissue
- bone, cartilage, tendons, and ligaments.
- Elastic fibers - provide strength and stretching capacity
- skin, blood vessels, and lungs.
- Reticular fibers -composed of collagen and glycoprotein
- support in walls of blood vessels, in spleen, in lymph nodes
- supporting network around fat cells, nerve fibers, muscle fibers.
- Cells
- Fibroblasts - connective tissue proper
- Chondroblasts - cartilage
- Osteoblasts - bone
- Hematopoietic stem cells - blood
- White blood cells, plasma cells, macrophages, and mast cells
- Classified by extracellular matrix
- Loose connective -Proper
- Mesenchyme - embryonic connective tissue
- Gel-like ground substance with fibers and star-shaped mesenchymal cells
- Gives rise to all other connective tissues
- Areolar
- Gel-like matrix with all three connective tissue fibers
- Fibroblasts, macrophages, mast cells, and some white blood cells
- Wraps and cushions organs
- Widely distributed throughout the body
- Adipose
- Reserves food stores, insulates against heat loss, and supports and protects
- Found under skin, around kidneys, within abdomen, and in breasts
- Local fat deposits serve nutrient needs of highly active organs
- Reticular
- Loose ground substance with reticular fibers
- Reticular cells lie in a fiber network
- Forms a soft internal skeleton, or stroma, that supports other cell types
- Found in lymph nodes, bone marrow, and the spleen
- Dense connective proper -more fibers; less cells and fluid
- Dense regular connective
- Mainly parallel collagen fibers with a few elastic fibers little fluid
- Major cell type is fibroblasts
- Attaches muscles to bone or to other muscles, and bone to bone
- Found in tendons, ligaments, and aponeuroses
- Dense irregular connective
- Irregularly arranged collagen fibers with some elastic fibers; little fluid
- Major cell type is fibroblasts
- Withstands tension in many directions providing structural strength
- Found in the dermis, submucosa of digestive tract, and fibrous organ capsules
- Elastic connective
- abundant in elastic fibers;
- some collagenous fibers; fibroblasts
- walls of large arteries, airways, heart
- Cartilage - solid but flexible gel like matrix
- Cells are called chondrocytes
- No blood vessels or nerves
- Classified by fiber type
- Hyaline cartilage
- Amorphous, firm matrix with imperceptible network of collagen fibers
- Chondrocytes lie in lacunae
- Supports, reinforces, cushions, and resists compression
- Forms the costal cartilage
- Found in embryonic skeleton, the end of long bones, nose, trachea, and larynx
- Fibrocartilage
- Matrix similar to hyaline cartilage but less firm with thick collagen fibers
- Provides tensile strength and absorbs compression shock
- Found in intervertebral discs, the pubic symphysis, and in discs of the knee joint
- Elastic cartilage
- Similar to hyaline cartilage but with more elastic fibers
- Maintains shape and structure while allowing flexibility
- Supports external ear (pinna) and the epiglottis
- Bone - Calcium matrix
- Hard, calcified matrix with collagen fibers found in bone
- Osteocytes are found in lacunae and are well vascularized
- Supports, protects, and provides levers for muscular action
- Stores calcium, minerals, and fat
- Marrow inside bones is the site of hematopoiesis
- Blood- Fluid matrix (plasma)
- Red and white cells in a fluid matrix (plasma)
- Contained within blood vessels
- Functions in the transport of respiratory gases, nutrients, and wastes
- Summary of Matching Function to Connective Tissue
- Skeletal
- Long, cylindrical, multinucleate cells with obvious striations
- Initiates and controls voluntary movement
- Found in skeletal muscles that attach to bones or skin
- Cardiac
- Branching, striated, uninucleate cells interlocking at intercalated discs
- Propels blood into the circulation
- Found in the walls of the heart
- Smooth
- Sheets of spindle-shaped cells with central nuclei that have no striations
- Propels substances along internal passageways (i.e., peristalsis)
- Found in the walls of hollow organs
- Branched neurons with long cellular processes and support cells
- Transmits electrical signals from sensory receptors to effectors
- Found in the brain, spinal cord, and peripheral nerves
- Causes inflammation, characterized by:
- Dilation of blood vessels
- Increase in vessel permeability
- Redness, heat, swelling, and pain
- Organization and restored blood supply
- The blood clot is replaced with granulation tissue
- Regeneration and fibrosis
- Surface epithelium regenerates and the scab detaches
- Fibrous tissue matures and begins to resemble the adjacent tissue
- Results in a fully regenerated epithelium with underlying scar tissue
Developmental Aspects
- Primary germ layers: ectoderm, mesoderm, and endoderm
- Three layers of cells formed early in embryonic development
- Specialize to form the four primary tissues
- Nerve tissue arises from ectoderm
- Muscle, connective tissue, endothelium, and mesothelium arise from mesoderm
- Most mucosae arise from endoderm
- Epithelial tissues arise from all three germ layers
Helpful Activities to do after you finish reading this chapter
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