Chapter 4: Tissues Flashcards
What is a tissue?
A tissue is a group of cells that function together to carry out specialized activities.
What are the 4 basic types of tissues
connective, epithelial, muscular and nervous
T or F: tissues can be made of 2 or more cell types
True
Any surface is covered by…
epithelial cells
Cell junctions
contact points between the plasma membranes of tissue cells
5 types of cell junctions
tight, adherins, desmosomes, hemidesmosomes, gap junctions
What do tight junctions inhibit
they inhibit the passage of substances between cells and prevent the contents of these organs from leaking into the blood or surrounding tissues. “water proof”
Adhering junctions
contain plaque, a dense layer of proteins inside the plasma membrane thay attaches to both membrane proteins and to micro filaments of the cytoskeleton. Uses cadherins. not water proof
Cadherins in adherent junctions
inserts into the plaque from the opposite side of the plasma membrane, partially crosses the intracellular space and connects to cadherins of the adjacent cell
Tight junctions
tight junctions consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between cells
Purpose of tight junctions
inhibit the passage of substances between cells and prevent the contents of these organs from leaking into the blood in surrounding tissues
Where are tight junctions found
tissues lining the surface of body cavities; stomach, intestines, urinary bladder
Desmosomes
contain plaque and have transmembrane glycoproteins (cadherins) that extend into the intracellular space between adjacent cell membranes and attach to one another. attach to intermediate filaments in the cytoskeleton
Where are desmosomes abundantly found
in the epidermis of the skin
Hemidesmosomes
resemble desmosomes but they do not link adjacent cells. they anchor cells not to eachother but to basement membranes.
What do hemidesmosomes use instead of cadherins
the transmembrane glycoproteins in hemidesmosomes are integrins rather than cadherin. Integrins attach to intermediate filaments made of the protein keratin.
Basement membranes location in directional terms
basement membranes are deep to the epithelium and superficial to the connective tissue.
Gap junctions
At gap junctions membrane proteins called connexins form tiny fluid filled tunnels called connexons that connect neighbouring cells.
Gap junctions allow;
electrical impulses to pass rapidly from one cell to another which allows for synchronous action.
What do connexons do
allow the ions and small molecules to diffuse from the cytosol of one cell to another, but the passage of large molecules such as vital intracellular proteins is prevented
Epithelial cells
are arranged in sheets and are densely packed with little extracellular matrix. mitosis occurs frequently
Function of basement membranes
thin extracellular layer that connects the epithelial cells to the underlying connective tissues.
Do epithelial tissues contain blood vessels?
no epithelial tissue is avascular but does have a nerve supply.
Name the different types of epithelial tissue cells
- simple squamous
- simple cuboidal
- nonciliated simple columnar
- ciliated simple columnar
- nonciliated pseudostratified columnar
- ciliated pseudostratified columnar
- stratified squamous
- stratified cuboidal
- stratified columnar
- urothelium
Simple squamous epithelium
single layer of flat cells that resembles a tiled floor when viewed from apical surface. Lines the cardiovascular and lymphatic system (called endothelium); forms epithelial layer of a serous membrane in abdominal and thoracic cavities
Function of simple squamous epithelium
present at sites of filtration (kidneys) or diffusion (lungs) and secretion in serous membranes
Simple cuboidal epithelium
single layer of cube shaped cells. covers surface of ovary, lines anterior surface of eye lens, lines kidney tubules and small ducts in glands.
Function of simple cuboidal epithelium
secretion and absorption; becayse nutrients only have to go through on layer of cells
Nonciliated simple columnar epithelium
- single layer of nonciliated column-like cells with oval nuclei near base of cells
- has microvilli on apical surface
- goblet cells in between that secrete mucus
- Lines GI tract, ducts of many glands and gallbladder
Function of nonciliated simple columnar epithelium
- secretion and absorption; mucus lubricates lining of digestive respiratory, and reproductive tracts and urinary tract
- helps prevent destruction of stomach lining by acidic stomach juices.
Ciliated simple columnar epithelium
single layer of ciliated columnlike cells with oval nuclei near the base of cells. Goblet cells usually interspersed. Lines some bronchioles, uterine tubes, uterus, paranasal sinuses
Function of ciliated simple columnar epithelium
In respiratory system, cilia beat in unison to move mucus and foreign particles toward throat to be coughed up or swallowed. Cilia also move oocytes(egg) from ovaries through the fallopian tubes into uterus.
Nonciliated pseudostratified columnar epithelium
appears to have several layers because nuclei are at various levels. even though the cells are attached to the basement membrane in a single layer, some cells do not extend to the apical surface. Does not contain goblet cells
Function of nonciliated pseudostratified columnar epithelium
absorption and secretion.
Ciliated pseudostratified columnar epithelium
appears to have several layers because cell nuclei are at various levels. all cells attached to basement menbrane in a single layer but some cells do not extend to apical surface. Contains cells that extend to the surface and secrete mucus (goblet cells) or bear cilia.
Ciliated pseudostratified columnar epithelium lines…
airways of most upper respiratory tract
Function of ciliated pseudostratified columnar epithelium
secretes mucus and traps foreign particles, and cilia sweep away mucus for elimination from body.
Stratified squamous epithelium
- contains 2 or more layers of cells; cells in apical layer and several layers deep to it are squamous –> cells in deeper layers are cuboidal and columnar. Keratinized variety forms superficial layer of skin. Nonkeratinized lines wet surfaces like (lining of mouth, esophagus, vagina)
Function stratified squamous epithelium
protection against abrasion, water low, UV radiation, and foreign invasion. First line of defense against microbes.
Stratified cuboidal epithelium
has 2 or more layers of cells; cells in apical layer are cube-shaped; fairly rare type. found in ducts of adult sweat glands, an part of male urethra
Function of stratified cuboidal epithelium
Protection; limited secretion and absorption . (limited because of multiple layers)
Stratified columnar epithelium
Basal layers consist of shortened, irregularly shaped cells; only apical layer has columnar cells; uncommon. Lines part of the urethra, small areas of anal mucous membrane, part of conjunctiva of eye.
Function of stratified columnar epithelium
protection and secretion
Urothelium
- cells will change shape
- in a relaxed or unstretched state, looks like stratified cuboidal epithelium, except apical layers tend to be large rounded.
- as tissues stretch, the cells become flatter giving the appearance of stratified squamous epithelium
Function of urothelium
Allows urinary organs to stretch and maintain protective lining while holding variable amounts of fluid without rupturing
Location of urothelium
lines urinary bladder, ureters, and portions of the urethra
Glandular epithelium
a gland is a single cell or a mass of epithelial cells adapted for secretion
Endocrine glands
secretions enter interstitial fluid and then diffuse into bloodstream without flowing through a duct.
Function of endocrine glands
hormones regulate many metabolic and physiological activities. to maintain homeostasis.
Exocrine glands
secretory products are released into ducts that empty onto the surface of a covering and lining epithelium, such as skin surface or lumen of lumen of hollow organ
Exocrine glands function
produce substances such as sweat to help lower body temperature, oil, ear wax, saliva or digestive enzymes
Goblet cells structural classification
unicellular- single cells
Sweat glands, oil glands, and salivary glands structural classification
multicellular- composed of many cells that form a distinctive microscopic structure or macroscopic organ
Merocrine secretion
individual product secreted via exocytosis. ex: salivary gland
Apocrine secretion
vesicles don’t fuse with cell membrane, portion of cell pinches off. ex: mammary gland
Holocrine secretion
entire cell dies and becomes a secretory product. ex: sebaceous glands on the skin that produce sebum that keeps the skin flexible and prevents it from drying out
Connective tissue; 2 basic elements
- connective tissue cells (lower in number and spaced apart)
- Extracellular matrix
Connective tissue does not form…
layers or sheets like epithelial tissue
what is extracellular matrix made of;
fibers (made of long proteins and ground substance (made pf protein and carbs)
Difference between epithelial and connective tissue
- connective tissue is highly vascularized and has a nerve supply
- connective tissue doesn’t form layers or sheets whereas epithelial tissue does
Connective tissue is highly vascularized and has a nerve supply with the exception of…
tendons and cartilage
Different types of connective tissue cells;
- reticular fibers
- fibroblasts
- colagen fibers
- mast cells
- plasmocytes
- neutrophils
- eosinophils
- adipocytes
- elastic fibers
- macrophages
Reticular fibers (connective tissue)
made of collagen and glycoproteins. they provide support in blood vessel walls and form branching networks around various cells (fat, smooth muscle, nerve)
Fibroblasts (connective tissue)
large flat cells that move through connective tissue and secrete fibers and ground substance
Collagen fibers (connective tissue)
strong, flexible bundles of the protein collagen, the most abundant protein in your body.
Mast cells (connective tissue)
abundant along blood vessels
- they produce histamine, which dilates small blood vessels during inflammation and kills bacteria
Plasmocytes (connective tissue)
develop from B cells
- they secrete antibodies that attack and neutralize foreign substances
Neutrophils (connective tissue)
white blood cells that migrate to sites of infection that destroy microbes by phagocytosis
Eosinophils (connective tissue)
white blood cells that migrate to sites of parasitic infections and allergic responses
Adipocytes (connective tissue)
are fat cells that store fats.
- they are found in the skin and around organs (heart, kidneys)
Elastic fibers (connective tissue)
stretchable but strong fibers made of proteins, elastin, and fibrillin. are able to expand
- found in skin, blood vessels and lung tissue .
Macrophages (connective tissue)
develop from monocytes and destroy bacteria and cell debris by phagocytosis
3 Fibers that make up the extracellular matrix
- Collagen fibers
- Elastic fibers
- Reticular fibers
provide strength and support tissue
Mesenchyme connective tissue
will eventually become every type of connective tissue
Mucoid (mucous) connective tissue
found in the umbilical cord
What are the two types of proper connective tissue and their subtypes?
Loose connective tissue: areolar, reticular, adipose
Dense connective tissue: regular, irregular, elastic
Areolar connective tissue (loose): function and location
function: strength, elasticity, support
location: in and around nearly every body structure thus called “packing material”
Reticular connective tissue (loose)
- secrete a fine network of thin, highly branched reticular fibers (net).
- form a supportive framework called stroma
- bind muscle cells together
Adipose connective tissue (loose)
- contain fat cells
- surrounded by scattered reticular fibers and has a rich vascular network
- provides insulation for maintaining body temperature
- stores fat and provides cushioning
Irregular connective tissue (dense)
densely packed collagen fibers arranged into irregular 3D networks and provide strength and resistance in all directions.
Regular connective tissue (dense)
called white fibrous tissue because of it’s white appearance.
- resists stress and pressure against one direction
Is there less ground substance in dense or loose tissue?
dense
What are the supporting connective tissues?
- cartilage
- bone
Hyaline cartilage
- most abundant cartilage in the body
- found at the end of long bones
- contains a resilient gel as ground substance and appears bluish white
Hyaline cartilage function
provides smooth surfaces for movement at joints, flexibility, and support; weakest type of cartilage and can be fractured
Fibrous cartilage
- strongest type of cartilage
- has chrondrocytes among clearly visible thick bundles of collagen fibers within extracellular matrix
- lacks perichondrium
What is a perichondrium?
dense layer of fibrous connective tissue that covers the surface of most cartilage in the body
Function of fibrous cartilage
- support and joining structures together
- strength and rigidity make it the strongest type of cartilage
Elastic cartilage
- has chondrocytes in a threadlike network of elastic fibers within the extracellular matrix
- perichondrium present
Elastic cartilage function
provides strength and elasticity; maintains shape of certain structures
Compact bone function
- supports soft tissues
- protects internal organs
- acts as levers during muscle contraction
- storage of calcium and phosphate
- resists stresses provided by weight, and movement
Spongy bone function
Trabeculae, the structural unit of a spongy bone, are arranged in an irregular lattice (criss cross pattern) providing space for red bone marrow
Liquid connective tissue - Blood
- consists of plasma and formed elements (RBCs, WBCs and platelets)
- within blood vessels ( arteries, arterioles, capillaries, veins and chambers of the heart)
Function of liquid connective tissue - blood
- RBCs; transport oxygen + some CO2
- WBCs: carry on phagocytosis and mediate allergic reactions and immune system responses
- Platelets: essential for clotting
Tissue membranes
flat sheets of pliable tissue that cover or line a part of the body
2 types of tissue membranes
- Epithelial membranes: mucous, serous, cutaneous
- Synovial membranes
Epithelial: mucous membrane
line body cavities hat ope to the outside, normally wet. example: mouth
Epithelial: serous membrane
- prevent damage to organs by moving
- line body cavities that do not open directly to the outside of the body
Epithelial: cutaneous membrane
the skin; both dermis and epidermis
Synovial membrane
secretes synovial fluid that line joints
3 types of muscular tissue
- skeletal muscle
- cardiac muscle
- smooth muscle
What does muscular tissue do?
consists of fibers that provide motion, maintain posture, and produce heat
Skeletal muscle function + location
- usually attach to bones by tendons
- motion, posture, heat production, and protection
- consist of long cylindrical striated fibers
- consciously controlled
Smooth muscle
- consist of nonstriated fibers
- spindle shaped cell, thickest in the middle
- unconsciously controlled
Smooth muscle location and function
- iris of eyes, walls of hollow organs such as blood vessels, stomach, urinary bladder
- motion (constriction, propulsion of foods through digestive canal, contraction of urinary bladder)
2 types of cells in nervous tissue
- neurons
-neuroglia
Neurons function and what they look like
- pass on signals
- neurons can carry sensory or motor information and they can perform integrative functions
- only one type but each cell looks different
- most neurons have a cell body, dendrites and axons (most length of the cell is in the axons)
Neuroglia
- protect and support neurons
- much smaller than neurons
What are considered excitable cells
neurons and muscle fibers are considered excitable cells because they inhibit electrical excitability
What is electrical excitability
the ability to respond to certain stimuli by producing electrical signals
Example of electrical excitability
Action potentials; which travel along the plasma membrane of a neuron or muscle fiber due to the presence of specific voltage gated channels
In patients who are brain dead what no longer occurs
brain is dead therefore no longer sends action potentials
Tissue repair
the process that replaces worn out damaged, or dead cells
Epithelial cells tissue repair
these cells are replaced by the division of stem cells or undifferentiated cells (replace themselves everyday)
Connective tissue cell repair
- not all connective tissue cells have the ability to repair
- example: cartilage tissue is avascular, so it repairs slowly (broken nose)
Muscle cells tissue repair
can perform limited repair, when we grow older we lose muscle
Nervous cells tissue repair
some nervous cells can perform limited repair, others cannot
Fibrosis
- the formation of scar tissue
- dead cells are replaced by fibroblasts
Why do fibroblasts look white
- fibroblasts don’t have blood supply, thats why scars look white
How does aging affect our tissues
- aging slows the process of tissue repair
- aging results in stiffening and loss of elasticity in tissues
Homeostatic imbalances in epithelial tissues
- disorders of epithelial tissues tend to be specific to organs such as ulcers in the stomach
Homeostatic imbalances in connective tissues
- disorders of connective tissues tend to be autoimmune in nature, such as lupus
