The Tissue Level of Organization Flashcards
What is human body tissue?
Collections of cells and cell products that perform specific, limited functions.
Tissues in combination form organs, such as the heart or liver
Four types if tissue
Epithelia
connective
muscle
nervous
Primary germ layers
-Superficial to deep: ectoderm, mesoderm, and endoderm
-formed early in embryonic development
-specialize to form the four primary tissues
-Nerve tissue arises from ectoderm
-Muscle and connective tissues arise from mesoderm
-Epithelial tissues arise from all three germ layers
Epithelia Tissue
-Are sheets of closely adhering cells covering external and internal body surface
-Form most glands-structures that produce secretions
Functions of epithelial tissue
-provide physical protection to deeper tissue
-produce specialized secretions (glandular epithelium)
-absorb chemicals including nutrients
-excrete waste
-provide sensation
Characteristics of epithelia
-Cellularity (cell junctions)
-Polarity (apical and basal surfaces)
-Attachment (basement membrane or basal lamina)
-Avascularity (does not have blood vessels) - usually nourished by underlying connective tissue
-regenration
Apical surfaces
-Microvilli increase absorption or secretion
-Cilia (ciliated epithelium) move substance over the epithelial surfaces
Basolateral surfaces
-Attachment to the basement membrane
-Epithelial maintenance and repair by division of germinative cells (stem cells) near basement membrane
-Intercellular connections (cell junction)
Attachment to the basement membrane
-Basal lamina the closest to the epithelium
-Reticular lamina
-Deeper portion of basement membrane
- provides strength
Epithelial maintenance and repair
-Epithelial cells are replaced by continual division of stem cells located near basement membrane
Intercellular connections
-Large areas of opposing cells membrane interconnected by transmembrane proteins (cell Adhesion Molecules “CAMs”)
-Specialized attachment sites that attach cell to another cell or extracellular material
Types of cell junctions
-Gap junctions
-Tight junction
-Desmosomes
Gap junction
-Allow rapid communication
-Are held together by channel proteins (junctional proteins, connexons)
-Allow ions to pass
-coordinate contraction in hear muscle
Tight junctions
-Between 2 plasma membranes
-Adhesion belt attaches to microfilaments of a terminal web
-Prevents passage of water and solutes
-Isolates waste in the lumen
Desmosomes
-Represent major intercellular adhesive junctions at basolateral membranes
-Mediate direct cell-cell contacts and provide anchorage sites for intermediate filaments important fro the maintenance of tissue architecture
Spot desmosome
Tie cells together an allow bending and twisting
Hemidesmosome
Attach cells to the basement membrane
Squamous
-Thin and flat
Cuboidal
-Square shaped
Columnar
-tall, slender rectangles
Simple epithelium
-Contains single layer of cells
-All cells touch the basement membrane
Stratified epithelium
-Contain several layers of cells
-Some cells rest on top of each other and don’t touch the basement membrane
-Named by shape of apical cells
Simple squamous epithelia
-Single layer of flattened cells with disc shaped central nuclei and sparse cytoplasm
-Mesothelium: Lines body cavities
-Endothelium: Forms inner lining of heart and blood vessels
Function: Reduces friction; controls vessel permeability; performs absorption and secretion
Stratified squamous epithelia
-Composed of several cell layers
- Basal cells are cuboidal or columnar and metabolically active (undergo continuous mitosis)
-daughter cells push towards the surface and become falter a they migrate upward-surface cells are “squamous”
Function: Provides physical protection against abrasion, pathogens, and chemical attack
Two types of stratified squamous epithelia
Keratinized
Non-kertinized
Keratnized
Keratin packed dead cells at the surface (skin)
Non- keratinized
Without surface layer of keratin at the surface (mouth, esophagus….)
Simple Cuboidal Epithelia
-Single layer of cubic like cells with large spherical central nuclei
Locations: Glands; ducts portions of kidney tubules; thyroid gland
Function: Limited protection, secretion, absorption
Stratified cuboidal epithelia
-Typically, two cell layers thick
-Located in ducts of sweat gland and larger ducts of mammary glands
Location: Lining of some ducts (rare)
Function: protection, secretion, absorption
Simple Columnar Epithelia
-Single layer of tall cell with round to oval nuclei
-Cells bear brush border of microvilli or ciliated in some organs
-May contain mucous secreting unicellular glands (goblet cells)
Location: Lining of stomach, intestine, gallbladder, uterine tubes, and collecting ducts of kidneys
Function: protection, secretion, absorption
Stratified columnar epithelia
-Rare type of epithelial tissue
-Composed of column shaped cells arranged in multiple layers.
Locations: Small areas of the pharynx, epiglottis, anus, mammary glands, salivary glands ducts, and urethra
Function: protection
Pseudostratified columnar epithelia
-Looks multilayered, but all cells touch basement membrane (but not all cells reaches the free surface)- falsely appears stratified
-Typically have cilia and goblet cells
-Goblet cells are mucus secreting cells in simple columnar and pseudostratified epithelia
Locations: lining of nasal cavity, trachea, and bronchi; portions of male reproductive tract
Functions: protection, secretion, move mucus with cilia
Transitional epithelia
-Multilayered Epithelium
-Surface cells appearance changes- dome shaped or squamous like depending on the degree of the organ stretch
-Tolerate repeated cycles of stretching without damage
Locations: Urinary bladder; renal pelvis; ureters
Functions: permits repeated cycles of stretching without damage
Glandular Epithelia
-Glands are collections of epithelial cells that produce secretions
Endocrine glands
-release hormones into interstitial fluid
-No ducts (ductless glands)
-Endocrine cells/Endocrine organs
-Exocrine glands produce secretions onto epithelial surfaces through ducts
Gland structure
-unicellular glands
-multicellular glands
Unicellular glands
-Mucous (goblet) cells are unicellular exocrine glands
-Scattered among epithelia
- For example, in intestinal lining
- Secrete mucin, which mixes with water to form mucus
Multicellular exocrine glands
-Structure of the duct
-Simple (undivided_
-Compound (divided)
-Shape of secretory portion of the gland
- Tubular (tube shaped)
- Alveolar or acinar (blind pockets)
-Relationsjip between ducts and glandular areas
-Branched (several secretory areas sharing one duct)
Simple tubular
Ex. Intestinal glands
Simple coiled tubular
Ex. Merocrine sweat glands
Simple branched tublar
Ex. Gastric glands of esophagus
Ex. Mucous glands of esophagus tongue, duodenum
Simple Alveolar (acinar)
Ex. Not found in adult; a stage in development of simple branched glands
Simple branched alveolar
Ex. Sebaceous (oil) glands
Compound Tubular
Ex. Mucous glands (in mouth)
Ex. Bulbo-urethral glands (in male reproductive system)
Ex. Testes (seminiferous tubules)
Compound Alveolar (acinar)
Ex. Mammary glands
Compound tublo-alveolar
Ex. Salivary glands
Ex. Glands of respiratory passages
Ex. Pancreas
Types of secretions
Serous glands, mucous glands, mixed exocrine glands
Serous glands
Watery secretions
Mucous glands
Secrete mucins
Mixed exocrine gland
Both serous and mucous
Modes of secretion
Merocrine secretion, apocrine secretion, holocrine secretion
Merocrine secretion
-The product is released from secretory vesicles at the apical surface of the gland cell by exocytosis
Apocrine secretion
-Involves the loss of apical cytoplasm. Inclusions, secretory vesicles, and other cytoplasmic components are shed in the process. The gland cell the grows and repairs itself before it releases additional secretions
Holocrine secretion
-Occurs as superficial gland cell burst. Continued secretion involves the replacement of these cells through the mitotic divisions of underlying stem cells
Connective tissue
-Diverse abundant type of tissue in which cells are not in direct contact with each others
Connective tissues
-Specialized cells
-Extracellular protein fibers
-Fluid called ground substance
Matrix
-Consists of extracellular components of connective tissue (fibers and ground substance)—accounts for most of the volume of connective tissue
Functions of connective tissues
-establishing a structural framework for the body
-transporting fluids and dissolved materials
-Supporting, surrounding, and interconnecting other types of tissue
-Storing energy reserves, especially triglycerides
-Defending the body from invading microorganisms
Many type of connective tissue based on the number of cells type, the relative properties and proportion of fibers and ground substance
Connective tissue proper
fluid connective tissue
supporting connective tissues
Mesenchyme
-Embryonic connective tissue
-Gives rise to all other connective tissues
-Not found in adults
-Gel-like ground substance with fibers and star-shaped mesenchymal cells
connective tissue proper has
-Varied cell population
-Matrix made up of extracellular fibers and viscous ground substance
Categories of connective tissue proper
-Loose connective tissue has more ground substance, fewer fibers. Ex.: fat (adipose tissue)
-Dense connective tissue has more fibers, less ground substance. Ex. tendone
Fibroblast
The most abundant in all connective tissue proper, secrete proteins and hylauronan
Fibrocytes
Second most abundant cell type, maintain connective tissue fibers
Adipocytes
Each cell stores a single, large fat droplet
Mesenchymal cells
Stem cells that respond to injury or infection, differentiate into fibroblasts, macrophages
Melanocytes
Synthesize and store the brown pigment melanin
Macrophages
Large phagocytic cells (Fixed macrophages stay in tissue, free macrophages migrate)
Mast cells
Stimulate inflammation after injury or infection, release histamine and heparin
Lymphocytes
Migrate throughout the body, may develop into plasma cells, which produce antibodies
Microphages
Phagocytic blood cells (neutrophils, eosinophils), attracted to signals from macrophages and mast cells
Fibers of connective tissue proper
Collagen, Reticular, Elastic
Collagen
-Most common fibers in connective tissue proper
-Long, straight, and unbranched
-Strong and flexible, resist force in one direction
-Abundant in tendon and ligaments
Reticular
-Branched collagenous fibers that form a network of interwoven fibers (stroma)
-Strong and flexible
-Resist forces in mamy direction
-Stabilize functional cells (parenchyma) and structures
Ex. Sheaths and organs
Elastic
-Contain elastin
-Long, thin fibers that allow for the stretch and return to original length after stretching
-Ex. elastic ligaments of vertebrae
Ground substance
-Is clear, colorless, and gelatinous to rubbery consistency
-Fills spaces between cells and surrounds tissue fibers
-Slows pathogens movement
Loose connective tissues
-Areolar tissue
-Adipose tissue
-Reticular tissue
Dense connective tissues
-Called collagenous tissues-contain many collagen fibers
-Three types of dense connective tissues
-dense regular
-dense irregular
-Elastic
Areolar CT
-Has all cell types: fibroblast, macrophages, mast cells, and some white blood cells,
-Gel like matrix with loosely organized fibers
-All three fiber types: mostly collagens but elastic and reticular also present
-Fibers are in all direction
-abundant blood vessels
Areolar Tissue L&F
Location: within and deep t the dermis of skin, and covered by epithelia lining of the digestive respiratory, and urinary tracts; between muscles; around joints, blood vessels, and nerves
Function: cushion organs; provides support but permits independent movement; phagocytic cells provide defense against pathogens
Adipose CT
-adipocytes (fat cells) are the dominant cell type
-Adipocytes in adults do not divide (expand to store fat, shrink as fats are released)
-Mesenchymal cells divide and differentiate to produce more fat cells when storage is needed
-adipocytes are empty looking cells with thin margin
-Nucleus pressed against cell membrane
White fat the main type (only fat in adult)
-Cushions organs such as eyeballs, kidneys
-Provide thermal insulation
-Contributes to body contours (female breast and hips)
Brown fat
-Found in babies and young children
-Adipocytes have many mitochondria
-Color comes from blood vessels and mitochondrial enzymes
-Function as heat generating tissue (breakdown of lipids releases energy and warms the body)
Adipose Tissue L&F
Loactions: deep to the skin, especially at sides, buttocks, and breast; padding around eyes and kidney
Function: provides padding and cushions shocks; insulates (reduce heat loss): stores energy
Reticular
-Network of reticular fibers in a typical loose ground substance, reticular cells lie on the network
RetIcular Tissue
Locations: liver, kidney, spleen, lymph nodes, and bone marrow
Function: provides supporting framework
Dense regular connective tissue
-Tightly packed, parallel collagen fibers
-Few elastic fibers
-Major cell type is the fibroblast (compressed between the collagen fibers)
Dense Regular Connective Tissue L&C
Locations: between skeletal muscles and skeleton (tendons and aponeuroses): between bones or stabilizing positions of internal organs (ligaments); covering skeletal muscles; deep fasciae
Functions: provides firm attachment; conducts pull of muscles; reduces friction between muscles; stabilizes positions of bones
Dense irregular connective tissue
-Irregular interwoven
-Some elastic fibers
-Major cell type is the fibroblast
Dense irregular connective tissue L&F
Locations: capsules of visceral organs; periostea and perichondria; nerve and muscle sheaths; dermis
Function: provides strength to resist forces from many direction; helps prevent over expansion of organs, such as the urinary bladder
Elastic Tissue
-Fibers are mostly elastic fibers
Elastic Tissue L&F
Locations: Between vertebrae of the spinal column (ligamentum flavum nuchae); ligaments supporting penis; ligaments supporting transitional epithelia; in blood vessel walls
Functions: stabilizes positions of the vertebrae and penis; cushions shocks; permits expansion and contraction of organs
What is fascia
-Connective tissue proper layers and wrappings that support and surround organs
-Facia can be divided into three layers
Superficial fascia
-Between skin and underlying organs
-Areolar tissue and adipose tissue
-Also know as subcutaneous layer or hypodermis
Deep fascia
-Bound to capsules, tendons, and ligaments
-Dense connective tissue
-Forms a strong. fibrous internal framework
Subserous fascia
-Between serous membranes and deep fascia
-Areolar tissue
Fluid connective tissue
-Fluid connective tissues include blood and lymph
Lymph
-Forms as interstitial fluid that enters lymphatic vessels
-Monitored by immune systems
-Returned to veins near the hart
Blood
-contains a watery matrix of dissolved proteins called plasma
-contain cells and cell fragments collectively known as formed elements
-Red blood cells (erythrocytes)
-White blood cells (leukocytes)
-Platelets
Supporting connective tissues:
-Support soft tissues and body weight
-include cartilage and bone
-Two types: Cartilage and bone
cartilage matrix
-is a firm gel
-Contains polysaccharide derivatives called chondroitin sulfates that form complexes with the protein fibers produce proteogylcans
-cells are only Chondrocytes found in chambers called lacunae
-have no blood vessels (avascular)
-Chondrocytes produce antiangiogenesis factor that inhibit the formation of blood vessels
Perichondrium
-Outer, fibrous layer (for strength)
-Inner, cellular layer (for growth and maintenance)
Types of cartilage
-Hyaline cartilage
-Elastic cartilage
-Fibrocartilage (fibrous cartilage)
Hyaline description
Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature (chondrocytes) line in lacunae
Hyaline function
supports and reinforces; has resilient cushioning properties; resists compressive stress
Hyaline location
Forms most of the embryonic skeleton; covers the ends of long bones in joint cavities; forms costal cartilages of the ribs; cartilages of the nose, trachea, and larynx
Elastic description
Similar to hyaline cartilage, but more elastic fibers in matrix
Elastic function
Maintains the shape of a structure while allowing great flexibility
Elastic location
supports the external ear (pinna); epiglottis
Fibrocartilage description
Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate
fibrocartilage function
Tensile strength with the ability to absorb compressive shock
Fibrocartilage location
Intervertebral discs; pubic symphysis; disc of knee join
Interstitial growth
-Chondrocyte undergoes division within a lacuna surrounded by cartilage matrix
-As daughter cells secrete additional matrix, they move apart, expanding the cartilage from within
Appositional growth
-Cells of the inner layer of the perichondrium differentiate into chondroblasts
-These immature chondroblasts secrete new matrix
-As the matrix enlarges, more chondroblasts are incorporated; they are replaced by stem cell divisions in the perichondrium
Bone (Osseous tissue)
-For weight support
-Calcified (made rigid by calcium salts)
-Resists shattering (flexible collagen fibers)
-Osteocytes (bone cells) lie in lacunae
Two types of bone tissue
-Compact bone
-Spongy bone
Compact bone
-Basic functional unit of compact bone is Haversian systems (or osteons)
Haversian systems (or osteons)
-Consists of concentric layers, or lamellae, of compact bone tissue that surround a central canal, the haversian canal
-The central haversian canal, and horizontal canals (perforating/Volkmann’s) canals contain vlood vessels and nerves from periosteum
Osteocytes
-Sit in their lacunae in concentric lamellae
-Canaliculi- small channels radiating from each lacuna to its neighbors allowing osteocy contact and exchange material with blood
Periosteum
-fibrous (outer) and cellular (inner) layers covering the whole bone
Bone (osseous tissue) description
hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae. Very well vascularized
Bone (osseous tissue) function
Bone supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other mineral and fat; marrow inside bones is the site for blood cell formation (hematopoiesis)
Bone (osseous tissue) location
Bones
Spongy bone
-Found in head of long bones and is the middle of flat bones
-Made of delicate struts of bone; trabeculae
-Covered with compact bone
Tissue membranes
-Physical barriers
-line or cover body surfaces
-Membrane may consist of:
-Only of Epithelium
-Only of connective tissue
- An epithelium supported by connective tissue
-Mucous membranes
- serous membranes
- Cutaneous membrane
Mucous Membranes (Mucosae)
-Line passageways that have external connections
-In digestive, respiratory, urinary, and reproductive tracts
-Epithelial surfaces must be moist
–To reduce friction
–To facilitate absorption and excretion
–Supported by lamina propria (areolar tissue)
Serous Membranes
-Made of simple squamous epithelium resting on a layer of areolar connective tissue
-Line cavities not open to the outside
-Have a parietal portion covering the cavity and a visceral portions (serosa) covering the organs
-Produce serous fluid to reduce friction
Three Serous Membranes
-pleura
-peritoneum
-pericardium
Pleura
-Lines pleural cavities (parietal layer) and covers the lungs (visceral layer)
Peritoneum
-Lines peritoneal cavity (parietal layer) and covers abdominal organs (visceral layer)
Pericardium
-Lines pericardial cavity (parietal layer) and covers heart (visceral layer)
Cutaneous Membrane
-The skin largest membrane of the body
-Made of stratified squamous epithelium (epidermis) resting on a layer of connective tissue (dermis)
Synovial membranes
-Line synovial joint cavities
-Movement stimulates production of synovial fluid for lubrication
-Lack a true epithelium
Excitable Tissues
-Tissue which are capable of generation and transmission of electrochemical impulses along the membrane
-There is two types of excitable tissue:
-Muscle tissue
-Nervous tissue
Muscle Tissue
-Specialized for contraction
-Three types of muscle tissue
-Skeletal muscle
-Cardiac muscle
-Smooth musvle
Skeletal muscle description
-Long, cylindrical, multinucleate cells; obvious striations
Skeletal Muscle Function
-Voluntary movement; locomotion; manipulation of the environment; facial expression; voluntary control
Skeletal Muscle Location
In skeletal muscles attached to bones or occasionally to skin
Cardiac muscle Description
Branching, striated, generally uninucleate cells that interdigitate at specialized junction (intercalate discs)
Cardiac muscle function
As it contracts, it propels blood into the circulation; involuntary control
Cardiac muscle location
the walls of the heart
Smooth muscle Description
Spindle-shaped cell with central nuclei; no striations; cells arranged closely to form sheets
Smooth cells function
Propels substances or objects (foodstuffs, urine, a baby) along internal passageways; involuntary control
Smooth cells location
Mostly in the walls of hollow organs
Neurons
-Detect stimuli and transmit coded information rapidly to other cells
-Cell body contains the nucleus and nucleolus
-Dendrites are short branches extending from the cell body
-Receive incoming signals
Axon (nerve fiber)
-long, thin extensions of the cell body
-Carries outgoing electrical signals to their destination
Neuroglia (supporting cells)
-Maintain physical structure of tissues
-Repair tissue framework after injury
-Perform phagocytosis
-Provide nutrients to neurons
-Regulate the composition of the interstitial fluid surrounding neurons
Nervous tissue description
-Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are non irritable supporting cells
Nervous tissue Function
-Transmit electrical signals from sensory receptors and to effectors (muscle and glands) which control their activity
Nervous tissue location
Brain, spinal cord, and nerves
Respones to tissue injury
-Tissues respond to injury involve three events
-Inflammation, granulation tissue formation, regeneration
Inflammatory response
-Injured cells and WBC’s release chemicals
- are become reddened, warm, swollen, and painful to touch
Granulation tissue formation
-Fibroblasts from the surrounding connective tissue replace the collagen and extracellular material lost by the injury
-Angiogenesis, the growth of new blood vessels, results in vascularization of the new tissue known as granulation tissue
-Epithelial cells migrate and replace destroyed epithelial cells
-Microphage digest the original blood cot
Regeneration and fibrosis
-Is the repair that occur after the damaged tissue has been stabilized and the inflammation subsidized
-Damaged tissue is replaced by the same type of tissue
-results in a fully regenerated epithelium with underlying scar tissue, which may or may not be visible
-Fibrosis: connective tissue (scar tissue) replaces some of the original tissue
Regenerative capacity of different tissues
-epithelia, connective tissues (except cartilage), and smooth muscle regenerate well
-Skeletal muscle, cardiac muscle, and nervous tissues regenerate poorly, if at all
-Damaged cardiac muscle cells are replaced by fibrous tissue through fibrosis
Speed and effectiveness of tissue regeneration decrease with age, due to
-Slowing of repair and maintenance activities
-Hormonal alterations
-Reduced physical activity
Effects of aging: chemical and structural tissue changes
-Thinner epithelia and more easily breached
-Fragile connective tissues
-Increased bruising
-Brittle bones
-Cardiovascular disease
-Muscle tissues, and nervous tissues begin to atrophy
-Mental deterioration
-DNA mutation increase cancer risk
Aging and cancer incidence
-Cancer rates increase with age
