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A&P Chapter 5

Terms in this set (100)

Tissues
-Groups of similar cells and extracellular material
-Common function
-E.g., providing protection
-Study of tissues, histology
Four types of tissues
-Epithelial, connective, muscle, nervous
-Varied structure and function
Epithelium, also referred to as epithelial tissue
--Composed of one or more layers of closely packed cells
-Contains little to no extracellular matrix
-Covers body surfaces
-Lines body cavities
-Forms majority of glands
Characteristics of Epithelial
-Cellularity
~Composed almost entirely of tightly packed cells
-Polarity
~Apical surface
>Exposed to external environment or internal body space
>Microvilli or cilia
~Lateral surface with intercellular junctions
~Basal surface
>Epithelium attached to connective tissue
-Attachment to basement membrane
~Three layers
>Lamina lucida, lamina densa, reticular lamina
>Composed of collagen, glycoproteins, and proteoglycans
~Barrier between epithelium and connective tissue
-Avascularity
~Nutrients obtained across apical surface or from basal surface
-Extensive innervation
~Detect changes in environment in that region
-High regeneration capacity
~Undergoes frequent cell division
~Regenerates at high rate
~Necessary due to environmental exposure
~Continual replacement of lost cells
>Cell division of stem cells
Functions of Epithelial Tissue
-Physical protection
~Protects external and internal surfaces
~Protects from dehydration, abrasion, destruction
-Selective permeability
~Relatively non-permeable to some substances
~Promotes passage of other molecules
-Secretions
~Some cells are specialized to secrete
~May be scattered among other cell types
~Some arranged in small, organized clusters
-Sensations
~Contain nerve endings
~Supply information to nervous system
>Info on touch, pressure, temperature, pain
~Specialized epithelium, neuroepithelium
>Houses cells responsible for sight, taste, smell, hearing, equilibrium
Classification of Epithelial Tissue
-Body has different types of epithelia
-Epithelia classification indicated by two-part name
~Number of epithelial cell layers
~Shape of cells at apical surface
Simple epithelium
-One cell layer thick
-All cells in direct contact with basement membrane
-In areas where stress is minimal
-Filtration, absorption, or secretion is primary function
-E.g., lining of air sacs of lungs, intestines, blood vessels
Stratified epithelium
-Two or more layers of epithelial cells
-Only basal layer in contact with basement membrane
-In areas subjected to mechanical stress
~Better able to resist wear and tear
~E.g., skin, lining of the esophagus, lining of urinary bladder
-Cells in basal layer
~Continuously regenerate as apical layer cells lost
Pseudostratified epithelium
-Appears layered
~Due to cells' nuclei distribution at different levels
-All cells attached to basement membrane
-Some do not reach the apical surface
-Simple epithelium
Squamous cells
-Flat, wide, irregular in shape
-Floor tile arrangement
-Nucleus flat
Cuboidal cells
-About as tall as they are wide
-Edges somewhat rounded
-Nucleus spherical and in center of cell
Columnar cells
-Slender and taller than they are wide
-Nucleus oval; oriented lengthwise in basal region
Transitional cells
-Change shape, depending on stretch of epithelium
-Located where epithelium stretches and relaxes
~E.g., lining of the bladder
-Polyhedral when epithelium relaxed
-More flat when epithelium stretched
Simple squamous epithelium
-Single layer of flat cells
-Spherical to oval nucleus
-Thinnest barrier
-Allows rapid movement of molecules across surface
-Lines air sacs of lungs (alveoli)
-Lines blood and lymph vessel walls (endothelium)
-Serous membrane of cavities (mesothelium)
Simple cuboidal epithelium
-Single layer
-Uniformly shaped cells
-About as tall as they are wide
-Centrally located spherical nucleus
-Designed for absorption and secretion
-Ideal for structural components of glands
~Thyroid gland
~Surface of ovary
~Walls of kidney tubules
~Secretory regions/ducts of most glands
Simple columnar epithelium
-Single layer of cells
-Taller than they are wide
-Oval nucleus, lengthwise in basal region
-Ideal for secretory and absorptive functions
-Two forms
~Nonciliated
~Ciliated
Nonciliated Simple columnar epithelium
-Contains microvilli
~Fuzzy structure—brush border
-Unicellular glands—goblet cells
~Secrete glycoprotein—mucin
~Forms mucus when mixed with water
-Lines most of digestive tract from stomach to anal canal
Ciliated Simple columnar epithelium
-Cilia project from apical surface
~Move mucus along
-Goblet cells interspersed
-Lines
~Bronchioles
~Uterine tubes
~Helps move oocyte from ovary to uterus
Pseudostratifed columnar epithelium
-Appears as multiple cell layers
-Not really stratified
~All cells in direct contact with basement membrane
~Nuclei scattered at different distances
~Not all cells reach apical surface
-Two forms
~Ciliated
~Nonciliated
Ciliated pseudostratifed columnar epithelium
-Contains cilia on apical surface
-Protective functions
-Goblet cells secrete mucin
~Traps foreign particles moved by cilia
-Located in large passageways of respiratory system
Nonciliated seudostratifed columnar epithelium
-Rare, lacks cilia, goblet cells
-Protective functions
-Occurs mainly in male urethra and epididymis
Stratified squamous epithelium
-Multiple cell layers
~Only deepest in direct contact with basement membrane
-Basal layers with cuboidal shape
-Apical cells with squamous shape
-Protects against abrasion and friction
-Stem cells in basal layer continuously divide
~Replace lost cells at surface
-Exists in keratinized and nonkeratinized forms
Keratinized stratified squamous epithelium
-Superficial layers of dead cells
-Cells lack nuclei, filled with keratin
-Cells in basal region migrate toward apical surface
-Fill with keratin and die
-Found in epidermis
Nonkeratinized stratified squamous epithelium
-All cells alive
-Kept moist with secretions (e.g., saliva, mucus)
-Lack keratin, protective protein
-Microscopically visible cell nuclei
-Lines
~Oral cavity, part of pharynx, esophagus, vagina, anus
Stratified cuboidal epithelium
-Two or more layers of cells
-Superficial cells cuboidal in shape
-Forms tubes and coverings
-Protection and secretion
-Forms walls of ducts in most exocrine glands
~Sweat glands, parts of male urethra, periphery of ovarian follicles
Stratified columnar epithelium
-Rare
-Two or more layers of cells
-Columnar cells at apical surface
-Protects and secretes
-Found in
~Large ducts of salivary glands
~Some segments of male urethra
Transitional epithelium
-Limited to urinary tract
-In relaxed state
~Basal cells cuboidal or polyhedral; apical cells large and rounded
-In stretched state
~Apical cells flattened
-Binucleated cells (two nuclei)
-Allows for stretching as bladder fills
Glands
-Individual cells or multicellular organs
-Epithelial tissue
-Secrete substances used elsewhere or for elimination
-May secrete
~Mucin
~Electrolytes
~Hormones
~Enzymes
~Urea (nitrogenous waste)
Endocrine glands
-Lack ducts
-Secrete hormones into blood
-Chemical messengers that influence cell activity elsewhere
Exocrine glands
-Invaginated epithelium in connective tissue
-Connected with epithelial surface by duct
~Epithelium-lined tube for gland secretion
-E.g., sweat glands, mammary glands, salivary glands
Unicellular exocrine glands
-Do not contain a duct
-Located close to epithelium surface
-Most common type is goblet cell
Multicellular exocrine glands
-Numerous cells
-Acini—cells clusters that produce secretions
-Ducts transport secretions to epithelial surface
-Surrounded by fibrous capsule
~Extensions of capsule—septa, partition gland into lobes
Anatomic Form of Glands
-Simple glands-->a single, unbranched duct
-Compound glands-->branched ducts
-Tubular glands-->secretory portion and duct same diameter
-Acinar glands-->secretory portion forms expanded sac
-Tubuloacinar gland-->both tubules and acini
Merocrine glands
-Package secretions into vesicles
-Release secretions by exocytosis
-Examples include
~Lacrimal (tear) glands
~Salivary glands
~Some sweat glands (eccrine glands)
~Exocrine glands of the pancreas
~Gastric glands of the stomach
Apocrine glands
-Apical membrane pinches off and becomes secretion
-Damage repaired by glandular cells
-Continue to produce new secretions in same manner
-Examples include
~Mammary glands
~Ceruminous glands of ear
Holocrine glands
-Formed from cells that accumulate product
-Cell disintegrates
-Viscous mixture of cell fragments and cell product
-Ruptured cells replaced
-Examples include
~Oil-producing glands in the skin (sebaceous glands)
Connective tissue
-Most diverse, abundant, and widely distributed of tissues
-Supports, protects, and binds organs
-Cells, protein fibers, and ground substance
-Examples
~Tendons, Ligaments, Adipose tissue, Cartilage, Bone, Blood
Characteristics of Connective Tissue
-Cells
~Classes of CT have specific cell types
~Most cells not in direct contact with each other
~Two classes of cells
>Resident cells
>Wandering cells
Resident cells
-Stationary, housed in CT
-Support, maintain, repair extracellular matrix
-Examples of resident cells
~Fibroblasts
>Flat cells with tapered ends
>Most abundant resident cells in CT proper
>Produce fibers and ground substance of extracellular matrix
~Adipocytes (fat cells)
>Appear in small clusters in some types of CT proper
>Adipose connective tissue—dominant area of large clusters
~Mesenchymal cells
>Embryonic stem cell
>Divides to replace damaged cells
>One replaces mesenchymal cell, other becomes committed cell
~Fixed macrophages
>Relatively large, irregular-shaped cells
>Derived from monocytes (white blood cells)
>Dispersed throughout matrix
>Phagocytize (engulf) damaged cells or pathogens
>Release chemicals that stimulate immune system/attract wandering cells
Wandering cells
-Continuously move through CT
-Components of immune system
-Repair damaged extracellular matrix
-Types of leukocytes, white blood cells
-Protect body from harmful agents
-Types of wandering cells
~Mast cells
>Small, mobile cells close to blood vessels
>Secrete heparin to inhibit blood clotting
>Secrete histamine to dilate blood vessels
~Plasma cells
>Form when B-lymphocytes are activated when exposed to foreign material
>Produce antibodies (proteins that immobilize foreign material)
~Free macrophages
>Mobile, phagocytic cells
>Function like fixed macrophages, yet able to move
~Other leukocytes
>Neutrophils: Phagocytizes bacteria
>T-lymphocytes: Leukocyte that attacks foreign materials
Protein fibers
-Strengthen and support tissue
-Three types: collagen fibers, reticular fibers, elastic fibers
-Collagen fibers
~Unbranched, "cable-like" long fibers
~Strong, flexible, and resistant to stretching
~Appear white in fresh tissue
~Numerous in tendons and ligaments
-Reticular fibers
~Similar to collagen fibers but thinner
~Form branching, interwoven framework
~Tough but flexible
~Abundant in stroma (CT framework) of
>Lymph nodes
>Spleen
>Liver
-Elastic fibers
~Contain protein elastin
~Branching wavy fibers
~Stretch and recoil easily
~Yellow in color when fresh
~Help structures return to normal shape after stretching
~Found in skin, arteries, lungs
...
--Noncellular material produced by CT cells
-Residence of CT cells and protein fibers
-Consistency:
~Viscous (e.g., blood)
~Semisolid (e.g., cartilage)
~Solid (e.g., bone)
-Ground substance + protein fibers = extracellular matrix
-Glycosaminoglycans (GAGs)
~Large molecule in ground substance
~Carbohydrate building blocks, some with attached amines
~Negatively charged and hydrophilic
~Charge attracts cations, water follows
~Types include
>Chondroitin sulfate
>Heparin sulfate
>Hyaluronic acid
-Proteoglycans
~Formed with GAG linked to a protein
~90% carbohydrate in the form of GAGs
~Large structure due to negative repelling charges
~Perform numerous important functions
-Adherent glycoproteins
~Proteins with carbohydrates attached
~Bond CT cells and fibers to ground substance
~Includes: fibronectin, fibrillin, laminin
Scurvy
-Collagen is an important protein
-Strengthens and supports almost all body tissues
-Vitamin C essential for healthy collagen fibers
-Scurvy caused by vitamin C deficiency
-Symptoms: weakness, gum ulceration, hemorrhages, abnormal bone growth
-Caused by nutritional deficiencies
-Treated by consuming foods high in vitamin C or supplements
Functions of Connective Tissue
-Physical protection
~Bones of skull and thoracic cage protect delicate organs
~Adipose tissue protects kidneys and eyes
-Support and structural framework
~Bones, body framework
~Place for muscle attachment
~Cartilage keeps trachea and bronchi open
~Supportive capsules around kidney and spleen
-Binding of structures
~Ligaments bind bone to bone
~Tendons bind muscle to bone
~Dense irregular tissue anchors skin to muscle and bone
-Storage
~Adipose CT is the major energy reserve
~Bone, primary reservoir for calcium and phosphorus
-Transport
~Blood carries nutrients, gases, wastes between regions of body
-Immune protection
~Leukocytes protects body against disease
~Immune response when necessary
~Extracellular matrix restricts movement of disease-causing organisms
Embryonic Connective Tissue
-Two types of embryonic CT: mesenchyme, mucous CT
-Mesenchyme
~First type of CT in developing embryo
~Star- or spindle-shaped cells
~Dispersed in ground substance with immature protein fibers
>Larger proportion of ground substance than mesenchymal cells
~Source of all other CT cells
~Adult CT often has mesenchymal stem cells
>Provide support in repair of tissue
-Mucous connective tissue
~Second type of embryonic CT
~More numerous immature protein fibers than in mesenchyme
~Found in umbilical cord only
Four types of tissues
-Epithelial, connective, muscle, nervous
-Varied structure and function
Epithelium, also referred to as epithelial tissue
--Composed of one or more layers of closely packed cells
-Contains little to no extracellular matrix
-Covers body surfaces
-Lines body cavities
-Forms majority of glands
Four types of tissues
-Epithelial, connective, muscle, nervous
-Varied structure and function
...
-Rare genetic disease of CT
-Causes skeletal, cardiovascular, and visual abnormalities
-Abnormal chromosome 15
-Symptoms
~Abnormally long fingers, toes, limbs
~Malformation of thoracic cage, vertebral column
~Easily dislocated joints, resulting from weak ligaments, tendons, and joint capsules
~Weakness in aorta and abnormal heart valves
~Slipped lens of the eye
-Often death before age 50 due to cardiovascular problems
-Early diagnosis/medical management allows long life span
Classification of Connective
-All CT derived from mesenchyme
-Mesenchyme differentiates into adult connective tissues types
~CT proper
~Supporting CT
~Fluid CT
-Connective tissue proper is divided into two categories
~Loose CT
~Dense CT
Loose CT
-Fewer cells and protein fibers than dense CT
-Protein fibers are sparse and irregularly arranged
-Abundant ground substance
-Body's "packing material", supports structures
-Three types
1. Areolar
2. Adipose
3. Reticular
Areolar CT
-Loose organization of collagen and elastic fibers
-Highly vasularized
-Contains all fixed and wandering cells of CT proper
-Ground substance is abundant and viscous
-Found in the papillary layer of dermis
-Major component of subcutaneous layer
-Surrounds organs, nerve and muscle cells, and blood vessels
Adipose CT (fat)
-Composed mostly of adipocytes
-Two types
~White (stores energy, acts as insulator, cushions)
~Brown (found in newborns, generates heat, lost as we age)
-Adipocyte number remains stable
-Weight gain/loss due to adipocytes enlarging or shrinking
Reticular CT
-Meshwork of reticular fibers, fibroblasts, leukocytes
-Structural framework of many lymphatic organs
~Spleen
~Thymus
~Lymph nodes
~Bone marrow
Dense CT
-Mostly protein fibers
-Less ground substance than loose CT
-Collagen fibers predominate
-Three categories
1. Dense regular
2. Dense irregular
3. Elastic
Dense regular CT
-Tightly packed, parallel collagen fibers
-Resemble stacked lasagna noodles
-In tendons and ligaments
~Stress typically applied in a single direction
-Few blood vessels
-Takes a long time to heal
Dense irregular CT
-Clumps of collagen fibers extend in all directions
-Provides support and resistance to stress in multiple directions
-Extensive blood supply
-Found in:
~Most of the skin dermis
~Periosteum of bone
~Perichondrium of cartilage
-Forms capsules around some internal organs
Elastic CT
-Branching, densely packed elastic fibers
-Able to stretch and recoil
-Found in
~Walls of large arteries
~Trachea
~Vocal cords
Supporting CT
2 Types: Cartilage and Bone
Cartilage
-Firm, semisolid extracellular matrix
-Collage and elastic protein fibers
-Chondrocytes—mature cells
~Occupy small spaces called lacunae
-Surrounded by a dense irregular CT covering
~Perichondrium
~Outer fibrous layer and inner cellular layer
-Stronger and more resilient than other CT
-More flexible than bone
-In areas of body that need support and must withstand deformation (e.g., tip of nose)
-Avascular in mature state
-Three types
1. Hyaline cartilage
2. Fibrocartilage
3. Elastic cartilage
Hyaline cartilage
-Most common type
-Clear, glassy appearance under microscope
-Chondrocytes irregularly scattered
-Surrounded by perichondrium
-Located in
~Nose, trachea, and larynx
~Costal cartilage
~Articular ends of long bones
~Most of fetal skeleton
Fibrocartilage
-Weight-bearing cartilage, resists compression
-Protein fibers in irregular bundles between chondrocytes
-Sparse ground substance
-No perichondrium
-Located in
~Intervertebral discs
~Pubic symphysis
~Menisci of knee joint
Elastic cartilage
-Flexible, springy cartilage
-Numerous densely packed elastic fibers
~Ensure tissue is resilient and flexible
-Resists deformational pressure
-Chondrocytes closely packed
-Surrounded by a perichondrium
-Located in external ear and epiglottis
Bone
-More solid than cartilage
-Greater support, but less flexible
-Organic components (collagen and glycoproteins)
-Inorganic components (calcium salts)
-Bone cells—osteocytes
~Housed within spaces in extracellular matrix called lacunae
-Two types
~Compact bone
~Spongy bone
Compact bone
-Perforated by neurovascular canals
-Cylindrical structures—osteons
-Display concentric rings of bone CT called lamellae
-Lamellae encircle central canal, location of blood vessels and nerves
Spongy bone
-Located in interior of bone
-Latticework structure, strong and lightweigh
Bone functions
-Levers for movement
-Supports tissues
-Protects vital organs
-Stores minerals, e.g., calcium and phosphorus
-Houses hemopoietic cells, which make blood cells
Fluid CT
Two types: blood, lymph
Blood
-Fluid connective tissue with formed elements
~Cells
~Erythrocytes transport respiratory gases
~Leukocytes protect against infectious agents
~Cellular fragments, called platelets, help clot blood
-Liquid ground substance is called plasma
~Dissolved proteins
~Transports nutrients, wastes, hormones
Lymph
-Derived from blood plasma
-No cellular components or fragments
-Ultimately returned to bloodstream
Muscle tissue
-Cells contract when stimulated
-Contraction causes movement
~Voluntary motion of body parts
~Contraction of heart
~Propulsion of material through digestive and urinary tracts
-Three types
1. Skeletal
2. Cardiac
3. Smooth
Skeletal muscle tissue
-Striated or voluntary muscle tissue
-Moves skeleton
-Long cylindrical cells
~Skeletal muscle fibers
-Arranged in parallel bundles that run length of entire muscle
-Multinucleated
-Alternating light and dark bands, striations
-Does not contract unless stimulated by somatic nervous system
~Voluntary
Cardiac muscle tissue
-Confined to middle layer of heart wall, myocardium
-Responsible for heart contraction to pump blood
-Visible striations
-Cells short and often bifurcating
-One or two nuclei
-Cells connected by intercalated discs
~Strengthen connection between cells
~Promote rapid conduction of electrical activity
-Involuntary
~Cannot be controlled by voluntary nervous system
~Pacemaker cells initiate contraction
Smooth muscle tissue
-Visceral or involuntary muscle tissue
-Lacks striations; appears smooth
-Cells are spindle-shaped
-Cells short with one central oval nucleus
-Found in walls of intestines, stomach, airways, bladder, uterus, blood vessels
-Helps propel movement through these organs
-No voluntary control over the muscle
Nervous tissue
-Located in the brain, spinal cord, and nerves
-Cells called neurons
~Receive, transmit, and process nerve impulses
-Larger number of glial cells
~Do not transmit nerve impulses
~Instead, are responsible for protection, nourishment, and support of neurons
Parts of a neuron
-Cell body
~Houses nucleus and other organelles
-Nerve cell processes extend from cell body
-Shorter and more numerous processes are called dendrites
~Receive incoming signals and transmit information
-Axon is the single long process extending from the cell body
~Carries outgoing signals to other cells
-Neurons are longest cells in the body
Organs
-Two or more tissue types
-Work together to perform specific complex functions
-Different structures must work in concert
-E.g., stomach, contains all four tissue types
The stomach
-Lined by epithelium
~Secretes substances for chemical digestion of nutrients
-Areolar and dense CT in walls
~Blood vessels and nerves
~Provides shape and support
-Three layers of smooth muscle in walls
~Contract and relax to mix stomach contents
-Abundant nervous tissue
~Responsible for regulating muscle contraction and gland secretion
Body membranes
-Formed from epithelial layer bound to underlying CT
-Line body cavities
-Cover viscera
-Cover body's external surface
-Four types
1. Mucous
2. Serous
3. Cutaneous
4. Synovial
Mucous membrane
-Mucosa
-Lines compartments that open to external environment
-Includes: digestive, respiratory, urinary, and reproductive tracts
-Performs absorptive, protective, and secretory functions
-Formed from epithelium and underlying CT
~CT component, lamina propria
~Covered with a layer of mucus derived from goblet cells, multicellular glands, or both
Serous membrane
-Lines body cavities that do not open to external environment
-Simple squamous epithelium (mesothelium)
-Produces thin, watery serous fluid
~Derived from blood plasma
~Reduces friction between opposing surfaces
-Forms parietal and visceral layers
-Serous cavity is in between
Cutaneous membrane
-Skin
-Covers external surface of body
-Composed of
~Keratinized stratified squamous epithelium
~Underlying CT
-Protects internal organs and prevents water loss
Synovial membrane
-Lines some joints in body
-Composed of
~Areolar CT
~Covered by squamous epithelial cells lacking basement membrane
-Synovial fluid secreted by epithelial cells
~Reduces friction among moving bone parts
~Distributes nutrients to cartilage
Stages of tissue development
-Oocyte fertilized by a sperm
-Forms diploid cell, zygote
-After multiple cell divisions, becomes blastocyst
-Cells forming embryo, embryoblast
-Three primary germ layers formed by 3rd week
~Ectoderm, mesoderm, endoderm
-Growing structure now an embryo
Ectoderm
-Initially located on dorsal and external embryo surfaces
-Responsible for forming many external structures
~E.g., epidermis of skin, hair, nails, exocrine glands
-Some, but not all, epithelial tissues derived from ectoderm
-Other structures derived
~Tooth enamel, eye lens, adrenal medulla, all nervous tissue
Mesoderm
-Middle primary germ layer
-Forms all muscle tissue
-Forms epithelial lining of vessels and serous membranes
-Becomes mesenchyme
~Later forms all CT in body
-Other mesoderm-derived structures
~Dermis, adrenal cortex, heart, spleen, kidneys and ureters, internal reproductive structures
Endoderm
-Becomes innermost germ layer
-Structures derived
~Epithelial linings of the tympanic cavity and auditory tube
~Epithelial linings of digestive, respiratory, reproductive, and urinary tract
~Thyroid gland, parathyroid gland, thymus
~Portions of palatine tonsils
~Most of liver, gallbladder, pancreas
Hypertrophy
Increase in size of existing cells of a tissue
Hyperplasia
Increase in number of cells of a tissue
Atrophy
-Shrinkage of tissue by decrease in cell number or size
-Due to normal aging or disuse
-E.g., bedridden individual
~Skeletal muscle fibers become smaller
~Reversible by physical therapy
Metaplasia
-Change of mature epithelium to a different form
-May occur as epithelium adapts to environment
-E.g., smokers
~Experience metaplastic changes in trachea epithelium
~Normal pseudostratified ciliated columnar epithelium changed
~Becomes nonkeratinized stratified squamous epithelium
~Will revert back quickly if person quits smoking
Dysplasia
-Abnormal tissue development
-May be precancerous, or revert back to normal
-Must be closely monitored by professionals
-E.g., cervical dysplasia due to exposure to human papillomavirus
Neoplasia
-Tissue growth is out of control
-Tumor of abnormal tissue develops
~Benign
>Localized growth
>Does not spread
~Malignant
>Metastasizes, spreads and invades other tissues
>Cancer
>Can interfere with normal functioning, leading to death
Necrosis
-Tissue death
-Due to irreversible tissue damage
-Inflammatory response to tissue damage
-E.g., gangrene
Gangrene
-Necrosis of soft tissues of a body part
-Due to diminished arterial blood supply
-Most common in limbs, fingers, toes
-Major complications of diabetes
Intestinal gangrene
-Follows obstruction of blood supply to intestines
-If untreated, leads to death
Dry gangrene
-Involved part is desiccated and shriveled
-Usually due to extreme cold
Gas gangrene
-Bacteria invade necrotic tissue
-Bacteria produce gas bubbles
Wet gangrene
-Caused by bacterial infection of tissues with lost blood supply
-Ruptured dying cells release fluid, allows bacteria to flourish
Aging of Tissues
-All tissues change with aging
-Proper nutrition, good health, normal circulation, infrequent wounds—all promote normal functioning
-Support, maintenance, replacement of cells and extracellular matrix
-Less efficient after middle age
-Structure and chemical composition of many tissues altered
~Epithelia thins
~CT loses pliability and resiliency
~Collagen declines
~Bones become brittle
~Muscles atrophy
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