The Tissue Level of Organization Flashcards
epithelial membranes
composed of epithelium attached to a layer of connective tissue
Mucous membranes (mucosa)
lines internal cavities and passageways that open externally. produces mucus and has underlying connective tissue (lamina propria) ex: respiratory, digestive tracts
serous membrane (serosa)
line cavities and organs that do not open externally. produces serous fluid. ex: pleura, pericardium,peritoneum
cutaneous membrane (skin)
cabers external body surface. keratinized cells protect the body from desiccation and pathogens
connective tissue membranes
composed of connective tissues but also has a synovial membrane which lines the internal cavity of moveable joints. Produces synovial fluid
What are the properties of epithelial tissue?
cells connected by celll junctions, with little extracellular material in between they are avascular so the thickness limits nutrients, waste exchange and life span. Also capable of reproduction because of wear and tear
What are the function of epithelial tissue?
Protection from mechanical and chemical injury, and from foreign pathogens
Sensory functions to monitor changes in the environment, eg skin, nose, eye, ear
Produces secretions, eg hormones, mucus, digestive juices, sweat
Barrier to control movement of gases, solutes and fluid across it
What’s the structure of epithelial tissue?
Organized into layers
Apical (free) surface: interacts with external environment
Basement membrane: permeable material (reticular and basal laminae) linked to connective tissue
Types of epithelial tissue
Membranous epithelium (covering or lining): lines serous cavities, blood & lymphatic vessels, respiratory, digestive, and genitourinary tracts Glandular epithelium: secretory units of endocrine and exocrine glands
What are the different cell junctions? and what do they do?
1.Anchoring junctions: common on lateral and basal surfaces of cells
provide strong and flexible connections.
- Desmosomes: cadherin (adhesion protein) link adjacent cell membranes
- Hemidesmosomes integrin (adhesion protein) link cells to basal lamina
- Adherens junctions actin (contractile protein) link patches or form a “belt” inside the cell: influence shape and folding of epithelial tissue.
5.Tight junctions: no extracellular space between cells
stops substances moving between cells and from one
separates cells into apical and basal compartments.
6.Gap junctions: form intercellular passageways between membranes of adjacent cells
Allow substances to move quickly and directly between cytoplasm of adjacent cells
Allow coordination of function in large groups of cells
Types of epithelial tissue based on layers
- Simple: single layer
- Stratified: 2 or more layers
- Pseudostratified: single layer that looks stratified
- Transitional: specialized stratified epithelium with shapes that stretch and change
Types of epithelial tissue based on shape of cells at the top layer
- Squamous: flattened and thin
- Cuboidal: boxy, as wide as it is tall
- Columnar: rectangular, taller than it is wide
what are Glands?
Gland are modified epithelium cells that can synthesize and secrete chemical substances. Most glands consist of groups of epithelial cells.
What are the different Types of Glandular Epithelium? Along with their description and some examples
- Exocrine Glands
Description: secretions leave through a duct that opens to the external environment
Examples: goblet cells, sweat glands, salivary glands, mammary gland
Types of Secretions: Mucous, sweat, saliva, and breast milk - Endocrine Glands
Description: ductless gland that releases secretions directly into surrounding tissues and fluids
Examples: anterior pituitary, thymus, adrenal cortex, and gonads
Types of Secretions: Hormones
What are the different Methods and Types of Exocrine Secretion?
- Merocrine secretion (most common type)
Secretions are enclosed in vesicles and released by exocytosis at apical surface of the cell: cause little damage to cell
Examples: watery mucous, eccrine sweat glands - Apocrine secretion
Secretions, together with part of the cell membrane, are pinched off and released: cause little damage to cell
Examples: apocrine sweat glands in axillary and genital areas - Holocrine secretions
Secretions are released when cell bursts: ruptures and destroys entire gland cell
Examples: sebaceous glands that produce oils on skin and hair
Different cell types in connective tissue
- Fibroblast (most common): Active cell that secretes polysaccharides and proteins (including fibers)
- Fibrocyte (2nd most common): less active (more mature) form of fibroblast
- Adipocyte: store lipids in cytoplasm
- Mesenchymal cell: multipotent adult stem cell: can differentiate within lineage for repair and healing
- Macrophage: phagocyte, immune cell derived from monocytes, also secretes cytokines to recruit other immune cells
- Mast cell: contains cytoplasmic granules filled with histamine and heparin that are involved in inflammatory response
Different Connective Tissue Fibers and the ECM
- Collagen fiber
Composition: fibrous protein subunits linked together to form long and straight fibers
Characteristics: Flexible with great tensile strength, resist stretching, resilient
Example: ligaments and tendons their characteristic and strength - Elastic fiber
Composition: contains elastin protein and some glycoproteins
Characteristics: Returns to original shape after being stretched or compressed
Example: elastic tissues in skin and the elastic ligaments of vertebral column. - Reticular fiber
Composition: Similar protein subunits to collagen fibers arranged in a branching network
Characteristics: Flexible with great tensile strength, resist stretching, resilient
Example: reticular tissue of soft organs (liver and spleen) to anchor and provide structural support to parenchyma - Extracellular matrix (ECM)
Composition: combination of proteins and polysaccharides (proteoglycans) and extracellular fluids (ground substance). Ground substance is usually fluid, but can also be mineralized and solid (bones)
Characteristics: attracts and traps available moisture to form clear, viscous, colorless matrix. Various types of connective tissue contain different amounts of cells and ECM.
Classification of connective tissues
- Connective tissue proper: variety of cell types and protein fibers suspended in a viscous ground substance.
Dense connective tissue: reinforced by bundles of fibers that provide tensile strength, elasticity, and protection. Dense regular connective, dense irregular connective
Loose connective tissue: loosely organized fibers with large spaces in between. Areolar, Adipose, Reticular - Supportive connective tissue: contains densely packed fibers in ECM, protects, provide structure and strength
Cartilage: Hyaline, fibrocartilage, elastic
Bone: rigid, calcified matrix. Compact bone, cancellous (spongy) bone - Fluid connective tissue: contains no fibers, cells circulate in watery fluid with salts, nutrients, dissolved proteins
Lymph, blood
Loose connective tissue
located between many organs, loose connective tissues absorb shock, bind tissues together, allow diffusion of water, salts, various nutrients to adjacent or imbedded cells and tissues.
What are the types of loose connective tissue?
- Adipose tissue: consist of fat storage cells with little extracellular matrix with a large number of capillaries allow rapid storage and mobilization of lipid molecules
- Areolar tissue: contains all cell types and fibers, distributed in a random, web-like fashion to fill spaces between muscle fibers, surrounds blood and lymph vessels, and supports organs
- Reticular tissue: mesh-like, supportive framework for soft organs (lymphatic tissue, spleen, liver)
Dense Connective Tissue
contains more collagen fibers compared to loose connective tissue to provide greater resistance to stretching great tensile strength and resists stretching in direction of fiber orientations. Can contain elastic fibers to regain original shape after stretching
What are the types of dense connective tissue?
- Dense regular connective tissue
fibers arranged parallel to each other: greater strength in one direction
Example: Ligaments, tendons - Dense irregular connective tissue
fibers arranged in random directions: greater strength in all directions, can regain original shape after stretching
Example: dermis of the skin, walls of arteries
Cartilage Tissue
Cartilage tissue is avascular: slow diffusion of nutrients through the matrix to reach the chondrocytes. This is a factor contributing to the very slow healing of cartilaginous tissues.
What are the Components of a cartilage?
- Chondroblasts: most active, developing cartilage cells
- Chondrocytes: less active and more mature cartilage cells
- Lacunae: Space occupied by chondrocytes
- Perichondrium: layer of dense irregular connective tissue that encapsulates the cartilage
- Extra cellular matrix (ECM): Contains chondroitin sulfates (polysaccharides) which bind with ground substance proteins to form proteoglycans
