Tissues Flashcards
Tissues
Groups of cells with similar structure and function, vary in content of extracellular matrix
Extracellular Matrix
Substance(s) produced by cells of a specific tissue, located on the outside of the cells, may contain protein fibers, salts, water, macromolecules
Four Primary Tissue Types
Epithelial (covering), Connective (support), Muscle (movement), Nervous (control)
Epithelial Tissue
- Lines the inside and outside of body surfaces, cavities and organs.
- Glands mostly derived from it
- Little/no ECM
Functions of Epithelium
- protection
- absorption, secretion, ion transport
- filtration
- forms slippery surfaces
Characteristics of Epithelia
- cells fit closely (“cellularity”)
- polarity (“apical” and “basal” surface w/ diff functions)
- junctions on lateral surfaces
- supported by connective tissue
- avascular
- innervated
- regenerate regularly
Apical Surface
“top” of cell, part of cell on cavity/lumen side, sometimes has cilia or microvilli
Basal Surface
“bottom” of cell, in contact with basement membrane
Lateral Surface
“sides” of cell, contain cell junctions (tight junctions, desmosomes, gap junctions)
Microvilli
Folded membrane extensions for increasing of surface area in absorptive cells (ex: small intestine)
Cilia
cytoskeletal “hairs” used for movement (ex: respiratory epithelia moving mucus out of lungs)
Tight Junction
- closely associated areas of two cells whose membranes join together forming a virtually impermeable barrier to fluid
- like “strips of velcro”
Desmosomes
- structure specialized for cell-to-cell adhesion
- localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes
Gap Junction
directly connects the cytoplasm of two cells, which allows various molecules and ions to pass freely between cells
Basal Lamina
non-cellular, avascular layer of fibrils & glycoproteins secreted by epithelia on their basal side to act as a selective filter
Basement Membrane
- thin sheet of fibers that underlies the epithelium
- is the fusion of two lamina, the basal lamina and the reticular lamina
Reticular Lamina
Connective tissue that makes up part of the basement membrane
Epithelium Nomenclature
- “first name” indicates number of cell layers (simple = one, stratified = more than one)
- “last name” describes shape of cells (squamous = wider than tall, cuboidal = cube, columnar = taller than wide)
Simple Squamous Epithelium
- one layer of flat cells with disc-like nuclei that bulge out slightly like an egg yolk
- Function: material transport via diffusion/filtration, secretion of lubricating substances
- Location: kidney glomeruli; alveoli, lining of heart, blood and lymph vessels, lining of ventral body cavities
Endothelium
- certain kind of simple squamous epithelium
- smooth lining to hollow heart, blood and lymph vessels
Mesothelium
- lines peritoneal, pleural and pericardial cavities (parietal)
- covers visceral organs (visceral)
Simple Cuboidal Epithelium
- single layer, cube-like cells w/ large spherical central nuclei
- Function: secretion, absorption
- Location: Kidney tubules, ducts and secretory portions of small glands, ovary surface
Simple Columnar Epithelium
- Single layer, column-shaped cells with oval nuclei toward the basal end
- may contain goblet cells
- Function: absorption, secretion of mucus, enzymes, etc.
- Location: (non-ciliated) digestive tract, gall bladder (ciliated) small bronchi, uterine tubes, parts of uterus
Goblet cells
simple columnar epithelial cells that line the intestines, respiratory tract and secrete mucus
Pseudostratified Columnar Epithelium
- single layer, cells of different heights
- false layered appearance
- may be ciliated
- Function: absorption, secretion, propulsion of mucus by cilia
- Location: (non-ciliated) ducts of large glands, sperm ducts, (ciliated) trachea, upper respiratory tract
Stratified Epithelia
- 2+ layers
- named according to shape of apical layer cells
- regenerate from below
- mostly for protection
Stratified Squamous Epithelia
- deeper layers cuboidal or columnar
- Function: protects underlying tissues from abrasion
- Keratinized or non-Keratinized
- Location: (non-keratin) moist linings of esophagus, mouth, vagina (keratin) epidermis
Keratin
- Keratin is a fibrous structural protein that forms epidermis, hair, nails
- Keratinized Stratified Squamous Epithelia have no nuclei to their apical layer because the cells are dead
Stratified Cuboidal Epithelium
- usually 2 layers
- Function: protection
- Location: large sweat gland ducts, mammary and salivary gland ducts
Stratified Columnar Epithelium
- rare
- Function: protection, secretion
- Location: male urethra, large ducts of some glands
Transitional Epithelium
- cells change shape, allows for stretching
- Basal cells cuboidal/columnar, Apical cells dome-shaped/squamous
- Function: permits distension of bladder, forms barrier for urine
- Location: lines ureters, bladder, part of urethra
Gland
one or more cells that secrete a particular product
Endocrine Gland
- lacks ducts
- secretes hormones directed at certain organs (“target” organs)
- use cardiovascular system to transport its products
Exocrine Gland
- empties through ducts to epithelial surface
- includes sweat/oil glands, mucus glands, salivary glands, liver, pancreas
Unicellular Exocrine Glands
- located within epithelium
- ex: goblet cell (secrets “mucin” which mixes w/ water to form mucus)
Multicellular Exocrine Glands
- formed by invagination of epithelium
- made up of a “duct” lined by epithelium and a “secretory unit” lined by secretory epithelium
- 1 name for duct structure, 1 for secretory unit
- ducts are either “simple” or “compound” (unbranched or branched)
- secretory units are “tubular” or “alveolar(/acinar)” or “tubuloalveolar” (some of both)
Connective Tissue
- most abundant tissue type
- underlies epithelium
- mostly well-vascularized (except tendons, ligaments, cartilage)
- fewer cells
- much more ECM
Connective Tissue ECM
- Ground Substance is polysaccharides, glycoproteins which hold tissue fluid and varies from soft, gel-like to hard, calcified
- Fibers: “collagen” for strength, “elastic” for stretch, “reticular” for delicacy
Loose Connective Tissue
- 3 types: Areolar, Adipose, Reticular
- Functions: support and binding of tissues (3 fiber types), holds tissue fluids (ground substance), stores nutrients (adipocytes), defends against infection
Defense Cells
- Macrophages (phagocytosis)
- Plasma Cells (antibody secretions)
- Mast Cells (inflammation)
- WBCs (neutrophils, eosinophils, lymphocytes)
Areolar Connective Tissue (Loose)
- most widely distributed (loose)
- contains all 3 fibers
- Fibroblasts are the resident cells, various defense cells too
- Function: wraps and cushions organs, phagocytosis, inflammation, hold tissue fluid
- Location: under epithelia, packages organs, surrounds capillaries
Adipose Connective Tissue (Loose)
- cells contain large lipid deposits w/ nuclei pushed to edge
- Function: insulation, protection, fuel storage
- Location: under skin, around kidneys/eyes, in abdomen/breasts
- resident cell is known as an Adipocyte
Brown Adipose Tissue
- smaller cells than regular adipose w/ numerous small fat droplets
- vascularized
- generate heat
- have many mitochondria
Reticular Connective Tissue (Loose)
- delicate fiber network
- Function: internal support of lymphoid organs, supports immune cells, allows for expansion/contraction
- Location: Spleen, Bone Marrow, Lymph Nodes
Dense Connective Tissue
- ECM is mostly collagen fibers
- resident cells are Fibroblasts
- 3 types: Irregular, Regular, Elastic
Dense Irregular Connective Tissue
- irregularly arranged collagen, some elastic fibers
- Function: withstand multi-directional tension, structural support
- Location: dermis, digestive submucosa, fibrous joint/organ capsules
Dense Regular Connective Tissue
- parallel collagen fibers, few elastin fibers
- Function: attach muscles and bones to each other, withstand high uni-directional stresses
- Location: tendons, ligaments, aponeuroses
Dense Elastic Connective Tissue
- high proportion of elastic fibers
- Function: allows recoil following stretching, maintains pulse in arteries, aids passive recoil of lungs after inspiration
- Location: walls of larger arteries, some ligaments of vertebral column, walls of bronchial tubes
Cartilage
- Firm, flexible tissue
- contains up to 80% water, collagen, ECM
- residents cells are Chondrocytes (Chondroblasts when immature) within Lacunae
- avascular and non-innervated
- 3 types: Hyaline, Elastic and Fibrocartilage
Hyaline Cartilage
- amorphous, firm matrix of imperceptible collagen network
- Function: support, resilient cushioning, resists compressive stress
- Location: embryonic skeleton, ends of long bones, costal (rib) cartilage, nose, trachea, larynx
Elastic Cartilage
- similar to hyaline w/ more elastic fibers
- Function: maintain shape/structure w/ high flexibility
- Location: support external ear (pinna), epiglottis
Fibrocartilage
- similar to but less firm than hyaline, mostly thick collagen fibers
- Function: tensile strength, shock absorption
- Location: intervertebral discs, pubic symphysis, discs of knee joint
Bone
- hard, calcified matrix w/ much collagen
- resident cell is Osteocyte (within lacunae, called Osteoblasts when immature)
- well vascularized
- Function: supports, protects, provides levers for muscle, store calcium, minerals, fat, hematopoiesis
- Location: bones!
Blood
- blood cells w/ fluid matrix (plasma)
- fibers visible during clotting (fibrin)
- Function: transport gases, nutrients, wastes, etc.
- Location: within blood vessels
Membranes
Four types:
- Cutaneous Membrane - skin (epidermis and dermis)
- Mucous Membrane - lines hollow organs open to outside (epithelium and areolar lamina propria)
- Serous Membrane - moist lining of closed cavities (mesothelium, submesothelial CT)
- Synovial Membrane - fibrous, lines all movable joint cavities
Muscle Tissue
- specialized for contraction
- elongated cells forming fibers
- function to produce movement
- 3 types: Skeletal, Smooth, Cardiac
Skeletal Muscle
- voluntary control
- attached to bone and skin
- cells are long, cylindrical, striated, multinucleate
- nuclei are at edge of cells to make room for myofilaments
Cardiac Muscle
- only in heart
- involuntary control
- contracts to propel blood through circulatory system
- cells are uninucleate with central nuclei, branched, striated and interdigitate at sites called intercalated disks
Smooth Muscle
- in walls of hollow organs
- constrict and relax involuntarily to move contents
- cells are uninucleate with central nuclei, spindle-shaped, unstriated, closely attached to each other
Nervous Tissue
- Main cells are neurons (electronically excitable cells), supporting cells are neuroglial cells
- Function: transmit electrical signals from sensory receptors and to effectors (muscles and glands)
- Location: brain, spinal cord, nerves
Dendrites
Branched projections of a neuron that conduct electrochemical signals
Axon
- AKA ‘nerve fiber’
- long, slender projection of neuron that conducts electrical impulses to other neurons, muscles and glands
