Tissues Flashcards
What are the functions of epithelial tissue?
- Protection
- Absorption
- Secretion
- Filtration
- Sensory reception
What are the characteristics of epithelial tissue?
- Closely-packed cells
- Polarity: apical vs. basal surfaces
- Avascular
- Mitotic
- Innervated
What type of cell junctions are present in epithelial tissue?
Tight Junctions
Impermeable junctions that prevent molecules from passing through the extracellular space between adjacent cells
Desmosomes
Anchoring junctions that bind adjacent cells together like molecular velcro
NO GAP JUNCTIONS
Basement Membrane
The junction point between the epithelial and connective tissue
Reticular Lamina
Extracellular layer that serves to anchor the basal lamina to underlying connective tissue
Basal Lamina
Extracellular layer that creates a barrier between epithelial tissue and connective tissue and sits on the side of the epithelial tissue
Microvilli
Increase surface area along the apical surface of epithelial tissue
Cilia
Move substances along apical surface of epithelial tissue in one direction
Types of Epithelia
Simple Squamous Epithelium
Single layer of flattened cells with disc-shaped central nuclei and sparse cytoplasm; the simplest of the epithelia
Function: Allows materials to pass by diffusion and filtration in sites where protection is not important; secretes lubricating substances in serosae
Simple Cuboidal Epithelium
Single layer of cubelike cells with large, spherical central nuclei
Function: Secretion and absorption
Simple Columnar Epithelium
Single layer of tall cells with round to oval nuclei; many cells bear microvilli, some bear cilia; layer may contain mucus-secreting unicellular glands (goblet cells)
Function: Absorption; secretion of mucus, enzymes, and other substances; ciliated type propels mucus (or reproductive cells) by ciliary action
Ciliated or Nonciliated Pseudostratified Columnar Epithelium
Single layer of cells of differing heights, some not reaching the free surface; nuclei seen at different levels; may contain mucus-secreting cells and bear cilia
Cilia are wispier than microvilli and the individual cilia are differentiable
Function: Secrete substances, particularly mucus; propulsion of mucus by ciliary action
Keratinized or Nonkeratinized Stratified Squamous Epithelium
Thick membrane composed of several cell layers; basal cells are cuboidal or columnar and metabolically active; surface cells are flattened (squamous); in the keratinized type, the surface cells are full of keratin and dead; basal cells are active in mitosis and produce the cells of the more superficial layers
Function: protects underlying tissues in areas subjected to abrasion
Stratified Cuboidal Epithelial
Epithelial tissue composed of multiple layers of cube-shaped cells. Only the most superficial layer is made up of cuboidal cells, and the other layers can be cells of other types; parts of tubes carrying secretions that are glandular in nature; often found in ducts but not a common cell type
Function: protection; secretion; absorption
Stratified Columnar Epithelium
Rare type of epithelial tissue composed of column-shaped cells arranged in multiple layers
Function: secretion and protection
Transitional Epithelium
Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells dome shaped or squamous-like, depending on the degree of organ stretch
Function: stretches readily, permits stored urine to distend urinary organ
Cells are ROUNDED at the apical surface
Merocrine Gland
Mode of secretion where secretory vesicles release their contents via exocytosis
Apocrine Gland
Mode of secretion where secretions bud off through the plasma membrane producing extracellular membrane-bound vesicles. The apical portion of the secretory cell of the gland pinches off and enters the lumen. It loses part of its cytoplasm in their secretions.
Memory aid: Apical surface/Apocrine
Holocrine Gland
Mode of secretion in exocrine glands where the secretions are produced in the cytoplasm of the cell and released by the rupture of the plasma membrane
Destroys the cell (suicidal) and results in the secretion of the product into the lumen
Memory aid: Whole cell/Holocrine
What types of fibers does connective tissue produce?
Collagen fibers are fibrous proteins and are secreted into the extracellular space and they provide high tensile strength to the matrix
Elastic fibers are long, thin fibers that form a branching network in the extracellular matrix; they help the connective tissue to stretch and recoil
Reticular fibers are short, fine collagenous fibers that can branch extensively to form a delicate network
Areolar Loose Connective Tissue
A type of connective tissue proper that packs material between other tissues, wraps and cushions organs; its macrophages phagocytize bacteria; plays important role in inflammation; holds and conveys tissue fluid
Adipose Loose Connective Tissue
Matrix as in areolar, but very sparse; closely packed adipocytes, or fat cells, have nucleus pushed to the side by large fat droplet
Function: Provides reserve food fuel; insulates against heat loss; supports and protects organs
Reticular Loose Connective Tissue
Loose network of reticular fibers (appear DARK and uniform thickness) in a gel-like ground substance; reticular cells lie on the network
Looks like a SPIDERWEB and traps foreign material; fibers form a soft internal skeleton (stroma) that supports other cell types including white blood cells, mast cells, and macrophages
Dense Regular Connective Tissue
Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast
Function: Attaches muscles to bones or to muscles; attaches bones to bones; withstands great tensile stress when pulling force is applied in one direction
Dense Irregular Connective Tissue
Primarily irregularly arranged collagen fibers; some elastic fibers; fibroblast is the major cell type
Function: withstand tension exerted in many directions, provides structural strength
Location: skin, fibrous coverings of some organs, around synovial joint capsules, submucosa of digestive tract
Dense Elastic Connective Tissue
Dense regular connective tissue containing a high proportion of elastic fibers
Function: allows tissue to recoil after stretching; maintains pulsatile flow of blood through arteries; aids passive recoil of lungs following inspiration
Location: walls of large arteries; within certain ligaments associated with the vertebral column; within the walls of the bronchial tube
Hyaline Cartilage
Amorphous but firm matrix; collagen fibers form an imperceptible network; chondroblasts produce the matrix and when mature chondrocytes) lie in lacunae
Fibers: dense network of collagen (strength) + elastic (flexibility) fibers (dark staining)
Function: support, aids in joint movement
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 Cartilage
Similar to hyaline cartilage, but more dark stained elastic fibers in matrix
Function: maintains the shape of a structure while allowing great flexibility
Location: supports the external ear (pinna); epiglottis
Fibrocartilage
Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate
Function: tensile strength allows it to absorb compressive shock
Location: compressive forces: intervertebral discs; pubic symphysis; discs of knee joint
Identifier: cell in a lacuna, fibrous collagen bundles (may have lines, but not dark lines), cells are lined up in a row
Bone
Hard, calcified matrix containing many collagen fibers; osteocytes lie in lacunae; very well vascularized
Function: Supports and protects (by enclosing); provides levers for the muscles to act on; stores calcium and other minerals and fat; marrow inside bones is the site for blood cell formation (hematopoiesis)
Two types: compact and spongy
Cutaneous Membrane
- Epithelium: Keratinized stratified squamous
- CT: Loose areolar + Dense irregular (predominant)
- Location: Skin
- Dry membrane
Serous Membrane
- ALWAYS: Epithelium (mesothelium) – Simple squamous
- ALWAYS: CT – Loose areolar [NOT Lamina Propria (mucous membrane)]
- Location: Lines body cavities/organs NOT open to exterior; Visceral vs. Parietal serosae
- Wet membrane – serous fluid (transudate)
Synovial Membrane
- Connective tissue only – Loose Areolar; Maybe some epithelial tissue, but not a complete layer
- Nourishes the hyaline cartilage
- Contains blood vessels
- Lines synovial joint cavities
- Wet membrane - synovial fluid
Nervous Tissue
Neurons are branching cells; cell processes that may be quite long extend from the nucleus-containing cell body; also contributing to nervous tissue are nonexcitable supporting glial cells
Function: neurons transmit electrical signals from sensory receptors and to effectors (muscles and glands); supporting cells support and protect neurons
Location: brain, spinal cord, nerves
Skeletal Muscle
- Long, cylindrical, multinucleated cells
- Striations
- Location: Attached to bones, eyeballs
- Voluntary contraction (conscious control)
Cardiac Muscle
- Branched, cylindrical cells, one nucleus
- Striations
-
Intercalated discs at cell junctions
- Gap junctions, Desmosomes
- Location: Heart
- Involuntary control
Smooth Muscle
- Sheets of tapered cells with central nuclei
- No striations
- Location: Walls of hollow organs
- Involuntary control
Looks like dense regular connective tissue but the shape of nuclei is oval and NOT linear (dense regular), more nuclei and packed than dense regular CT
