CH.4 : THE TISSUE LEVEL OF ORGANIZATION Flashcards
What is tissue made up of?
-a group of cells that usually have a common origin in an embryo and function together to carry out specialized activities.
What is histology?
study of tissues
Body tissues can be classified into four basic types according to their structure and function, name and explain them.
1) Epithelial tissues cover body surfaces and line hollow organs, body cavities, and ducts; they also forms glands.
- allows body to interact with internal and external environments.
2) Connective tissues protect and support the body and its organs.
- bind organs together, store energy reserves as fat, and help provide the body with immunity to disease-causing organisms
3) Muscular tissues are specialized for contraction and generation of force.
- generate heat
4) Nervous tissue detects changes in conditions inside and outside the body and responds by generating nerve action potentials that activate muscular contractions and glandular secretions
What are cell junctions?
-contact points between the plasma membranes of tissue cells.
What are the 5 most important cell junctions?
- tight junctions, adherens junctions, desmosomes, hemidesmosomes, and gap junctions
Explain tight junctions. What type of tissue are they found in?
- consist of weblike strands of transmembrane proteins that fuse together the outer surfaces of adjacent plasma membranes to seal off passageways between adjacent cells
- epithelial tissues that line the stomach, intestines, and urinary bladder have many
Explain adherens junctions. What type of cell are they found in?
- contain plaque, a dense layer of proteins on the inside of the plasma membrane that attaches both to membrane proteins and to microfilaments of the cytoskeleton
- Transmembrane glycoproteins called cadherins join the cells.
- in epithelial cells, adherens junctions often form extensive zones called adhesion belts because they encircle the cell similar to the way a belt encircles your waist.
Explain desmosomes. Where are they found?
- contain plaque and have transmembrane glycoproteins (cadherins)
- plaque attaches to intermediate filaments, which consist of the protein keratin.
- common among cells that make up epidermis and among cardiac muscle cells in heart.
Explain hemidesmosomes.
- transmembrane glycoproteins are integrins
- on inside of plasma membrane, integrins attach to intermediate filaments made of protein keratin.
- On the outside of plasma membrane, the integrins attach to protein laminin, which is present in the basement membrane
- anchor cells not to each other but to the basement membrane
Explain gap junctions.
- membrane proteins called connexins form tiny fluid-filled tunnels called connexons that connect neighboring cells
- plasma membrane is separated by a very narrow intercellular gap (space).
- through connexons, small molecules can diffuse from cytosol of one cell to another, but passage of large molecules is prevented
- allow cells in tissue to communicate with one another
What are the major differences between epithelial tissue and connective tissue?
Epithelial tissue :
- cells are tightly packed together with little or no extracellular matrix
- has no blood vessels (avascular meaning that they rely on blood vessels of the adjacent connective tissue to bring nutrients and remove wastes)
- almost always form surface layers and are not covered by another tissue
Connective tissue:
- a large amount of extracellular material separates cells that are usually widely scattered.
- have significant networks of blood vessels
What are the 3 main functions of epithelial tissue?
(1) selective barriers that limit or aid the transfer of substances into and out of the body
(2) secretory surfaces that release products produced by the cells onto their free surfaces
(3) protective surfaces that resist the abrasive influences of the environment
The various surfaces of epithelial cells often differ in structure and have specialized functions. Name all 3 surface types and explain them.
- apical (free) surface (most superficial layer) faces the body surface, a body cavity, the lumen (interior space) of an internal organ, or a tubular duct that receives cell secretions
- lateral surfaces, which face the adjacent cells on either side, may contain tight junctions, adherens junctions, desmosomes, and/or gap junctions.
- basal surface is opposite the apical surface
- basal surfaces of deepest layer adhere to extracellular materials such as the basement membrane
What is the basement membrane?
- a thin extracellular layer that commonly consists of two layers, the basal lamina and reticular lamina.
- form a surface along which epithelial cells migrate during growth or wound healing, restrict passage of larger molecules between epithelium and connective tissue, and participate in filtration of blood in the kidneys
What is the basal lamina? (one part of basement membrane)
- is closer to—and secreted by—the epithelial cells
- contains proteins such as laminin and collagen, as well as glycoproteins and proteoglycans.
- laminin molecules in the basal lamina adhere to integrins in hemidesmosomes and thus attach epithelial cells to the basement membrane
What is the reticular lamina? (second part of basement membrane)
-closer to the underlying connective tissue and contains proteins such as collagen produced by connective tissue cells called fibroblasts
Epithelial tissues may be divided into two types. Explain them.
(1) Covering and lining epithelium forms the outer covering of the skin and some internal organs.
- forms inner lining of blood vessels, ducts, and body cavities, and interior of respiratory, digestive, urinary, and reproductive systems
(2) Glandular epithelium makes up secreting portion of glands such as the thyroid gland
Types of covering and lining epithelial tissues are classified according to two characteristics: the arrangement of cells into layers and the shapes of the cells. Explain the 3 types of arrangement of cells in layers.
- Simple epithelium is a single layer of cells that functions in diffusion, osmosis, filtration, secretion, or absorption.
- Pseudostratified epithelium has multiple layers of cells because the cell nuclei lie at different levels and not all cells reach the apical surface, but it is actually a simple epithelium because all its cells rest on the basement membrane
- Stratified epithelium consists of two or more layers of cells that protect underlying tissues in locations where there is considerable wear and tear.
Types of covering and lining epithelial tissues are classified according to two characteristics: the arrangement of cells into layers and the shapes of the cells. Explain the 4 types of cell shapes.
1) Squamous cells are thin, which allows for the rapid passage of substances through them.
2) Cuboidal cells are as tall as they are wide and are shaped like cubes or hexagons. They function in either secretion or absorption
3) Columnar cells are much taller than they are wide, like columns, and protect underlying tissues. They often are used for secretion and absorption.
4) Transitional cells change shape, from squamous to cuboidal and back, as organs such stretch to a larger size and then collapse to a smaller size.
Simple squamous epithelium. Location and function?
(1) lines the cardiovascular and lymphatic system
(2) forms the epithelial layer of serous membranes
- filtration, diffusion and secretion
Simple cuboidal epithelium. Location and function?
- Covers surface of ovary; lines anterior surface of capsule of lens of the eye etc..
- Secretion and absorption
Nonciliated simple columnar epithelium. Location and function?
- Lines gastrointestinal tract (from stomach to anus), ducts of many glands, and gallbladder
- Secretion and absorption
Ciliated simple columnar epithelium. Location and function?
- Lines some bronchioles (small tubes) of respiratory tract, uterine (fallopian) tubes, uterus, and ventricles of brain.
- Cilia move mucus and foreign particles toward throat, where they can be coughed up and swallowed or spit out.
- also help move oocytes expelled from ovaries through uterine tubes into uterus.
Pseudostratified columnar epithelium, Location and function?
- Ciliated lines airways of most of upper respiratory tract
- nonciliated lines larger ducts of many glands, epididymis, and part of male urethra
- Ciliated secretes mucus that traps foreign particles, and cilia sweep away mucus for elimination from body;
- nonciliated functions in absorption and protection.
Stratified squamous epithelium, Location and function?
- Keratinized variety forms superficial layer of skin;
- nonkeratinized variety lines wet surfaces (lining of mouth, esophagus, part of epiglottis, part of pharynx, and vagina) and covers tongue.
- Protection against abrasion, water loss, ultraviolet radiation, and foreign invasion.
Stratified cuboidal epithelium, location and function?
- Ducts of adult sweat glands and esophageal glands, part of male urethra
- Protection; limited secretion and absorption.
Stratified columnar epithelium, location?
- Lines part of urethra; large excretory ducts of some glands, such as esophageal glands; small areas in anal mucous membrane; part of conjunctiva of eye.
- Protection and secretion.
Transitional epithelium, location?
- Lines urinary bladder and portions of ureters and urethra.
- Allows urinary organs to stretch and maintain protective lining while holding variable amounts of fluid without rupturing
What is a gland?
may consist of a single cell or a group of cells that secrete substances into ducts (tubes), onto a surface, or into the blood.
-All glands of the body are classified as either endocrine or exocrine.
What do endocrine glands (hormones) do? Location example?
- enter interstitial fluid and diffuse directly into bloodstream without flowing through a duct
- Examples include pituitary gland at base of brain
- regulate many metabolic and physiological activities to maintain homeostasis
What do exocrine glands (hormones) do? Location example?
- Secretory products released into ducts that empty onto surface of a covering and lining epithelium, such as skin surface
- Sweat for ex
- Produce substances such as sweat to help lower body temperature, oil, earwax, saliva, or digestive enzymes
Exocrine glands are classified as_____ or _______.
unicellular, multicellular
_____ cells are important unicellular exocrine glands that secrete mucus directly onto the apical surface of a lining epithelium.
Goblet
Multicellular glands are categorized according to two criteria:
(1) whether their ducts are branched or unbranched
(2) the shape of the secretory portions of the gland
What is a simple gland?
If the duct of the gland does not branch, it is a simple gland.
What is a compound gland?
If the duct branches, it is a compound gland.
What are tubular glands?
Glands with tubular secretory parts are tubular glands;
What are acinar glands?
those with rounded secretory portions are acinar glands (also called alveolar glands)
What are tubuloacinar glands?
Tubuloacinar glands have both tubular and more rounded secretory parts.
Multicellular exocrine glands: Simple glands: Explain simple tubular and give an example.
Tubular secretory part is straight and attaches to a single unbranched duct.
Example: glands in the large intestine
Multicellular exocrine glands: Simple glands: Explain simple branched tubular and give an example.
Tubular secretory part is branched and attaches to a single unbranched duct.
Example: gastric glands.
Multicellular exocrine glands: Simple glands: Explain simple coiled tubular and give an example.
Tubular secretory part is coiled and attaches to a single unbranched duct.
Example: sweat glands.
Multicellular exocrine glands: Simple glands: Explain simple acinar and give an example.
Secretory portion is rounded and attaches to a single unbranched duct.
Example: glands of the penile urethra.
Multicellular exocrine glands: Simple glands: Explain simple branched acinar and give an example.
Rounded secretory part is branched and attaches to a single unbranched duct.
Example: sebaceous glands
Multicellular exocrine glands: Compound glands: Explain compound tubular and give an example.
Compound tubular. Secretory portion is tubular and
attaches to a branched duct. Example: bulbourethral
(Cowper’s) glands
Multicellular exocrine glands: Compound glands: Explain compound acinar and give an example.
Compound acinar. Secretory portion is rounded and attaches to a branched duct.
Example: mammary glands
Multicellular exocrine glands: Compound glands: Explain compound tubuloacinar and give an example.
Compound tubuloacinar. Secretory portion is both tubular and rounded and attaches to a branched duct.
=Example: acinar glands of the pancreas
The functional classification of exocrine glands is based on what?
how their secretions are released.
How do secretions of merocrine glands work? Examples?
- synthesized on ribosomes attached to rough ER; processed, sorted, and packaged by the Golgi complex; and released from the cell in secretory vesicles via exocytosis
- Examples include the salivary glands and pancreas.
How do secretions of apocrine glands work?
-accumulate their secretory product at the apical surface of the secreting cell. Then, that portion of the cell pinches off by exocytosis from the rest of the cell to release the secretion
Most exocrine glands of the body are ___ glands
merocrine
How do secretions of holocrine glands work? Example?
- accumulate a secretory product in their cytosol.
- As the secretory cell matures, it ruptures and becomes the secretory product
- One example is a sebaceous gland of the skin
What do connective tissues do?
- bind together to strengthen body tissues; protect organs; compartmentalize skeletal muscles; serve as the major transport system within the body (blood); are the primary locations of stored energy reserves (fat tissue); and are the main source of immune responses
Connective tissues consist of two basic elements: what are they?
extracellular matrix and cells.
In terms of the extracellular matrix of connective tissue, what does it consist of?
- consists of protein fibers and ground substance, the material between the cells and the fibers.
- extracellular fibers are secreted by connective tissue cells and control the surrounding watery environment via specific proteoglycan molecules
Also, unlike epithelial tissues, connective tissues usually are highly ___; that is, they have a rich blood supply
vascular
Embryonic cells called ___ cells give rise to the cells of connective tissues
mesenchymal
Each type of connective tissue contains an immature class of cells with a name ending in -___, which means “to bud or sprout”. These immature cells are called ___ in loose and dense connective tissue, _____in cartilage, and ____ in bone .
-blasts
fibroblasts, chondroblasts, osteoblasts
In cartilage and bone, once the extracellular matrix is produced, the immature cells differentiate into mature cells with names ending in -___, namely, ___ and ____. Mature cells have reduced capacities for cell division and extracellular matrix formation and are
mostly involved in monitoring and maintaining the extracellular matrix.
-cyte, chondrocytes, osteocytes
Name all 6 types of cells in connective tissues.
1) Fibroblasts
2) Macrophages
In connective tissues, explain fibroblasts.
are large, flat cells with branching processes. They migrate through the connective tissues, secreting the fibers and components of the ground substance of the extracellular matrix.
In connective tissues, explain macrophages.
- develop from monocytes, a type of wbc.
- irregular shape with short branching projections and are capable of engulfing bacteria and cellular debris by phagocytosis.
- Fixed macrophages reside in a particular tissue;
- Wandering macrophages can move throughout tissue to carry on phagocytosis (fight infection)
In connective tissues, explain plasma cells.
- are small cells that develop from a type of wbc called a B lymphocyte.
- secrete antibodies
- in gastrointestinal and respiratory tracts.
- also abundant in the salivary glands, lymph nodes, spleen, and red bone marrow
In connective tissues, explain mast cells.
-They produce histamine, a chemical that dilates small blood vessels as part of the inflammatory response, the body’s reaction to injury or infection
In connective tissues, explain adipocytes.
- also called fat cells or adipose cells, store triglycerides - found deep to the skin and around organs such as the heart and kidneys
In connective tissues, explain white blood cells.
- in response to certain conditions they migrate from blood into connective tissues.
Each type of connective tissue has unique properties, based on the specific extracellular materials between the cells. The extracellular matrix consists of two major components: what are they?
(1) the ground substance : supports cells, binds them together, stores water, and provides a medium for exchange of substances between blood and cells.
(2) the fibers
What is ground substance made up of?
- contains water, polysaccharides and proteins.
- The polysaccharides include hyaluronic acid, chondroitin sulfate, dermatan sulfate, and keratan sulfate which are all referred to as glycosaminoglycans (GAGs)
- Except for hyaluronic acid, the GAGs are associated with proteins called proteoglycans
What are proteoglycans?
- glycosaminoglycans in ground substance are associated with them
- they form a core protein and the GAGs project from the protein
What does hyaluronic acid do? Found where?
- viscous, slippery substance that binds cells together, lubricates joints, and helps maintain the shape of the eyeballs.
- found in the ground substance of extracellular material of connective tissue
White blood cells, sperm cells, and some bacteria produce____, an enzyme that breaks apart hyaluronic acid, thus causing the ground substance of connective tissue to become more liquid.
hyaluronidase
____ sulfate provides support and adhesiveness in cartilage, bone, skin, and blood vessels.
Chondroitin
The skin, tendons, blood vessels, and heart valves contain____ sulfate; bone, cartilage, and the cornea of the eye contain___ sulfate
dermatan, keratan
Also present in the ground substance are ___ proteins, which are responsible for linking components of the ground substance to one another and to the surfaces of cells. The main adhesion protein of connective tissues is____, which binds to both collagen fibers and ground substance, linking them together.
adhesion, fibronectin
What are the 3 types of fibers embedded in the extracellular matrix between the cells of connective tissue?
collagen fibers, elastic fibers, and reticular fibers
What are collagen fibres?
- strong and resist pulling forces
- often occur in parallel bundles which adds great tensile strength to the connective tissue.
- consist of the protein collagen, which is the most abundant protein in your body
- found in bone, cartilage, tendons, and ligaments
What are elastic fibres?
- smaller than collagen fibers, branch and join together to form a fibrous network in connective tissue
- consists of molecules of the protein elastin surrounded by a glycoprotein, fibrillin, which adds strength and stability.
- strong but can be stretched and returned to original shape
- plentiful in skin, blood vessel walls, and lung tissue.
What are reticular fibres?
- consisting of collagen arranged in fine bundles with a coating of glycoprotein, provide support in the walls of blood vessels and form a network around the cells in some tissue
- Produced by fibroblasts, they are much thinner than collagen fibers and form branching networks.
- provide support and strength.
- plentiful in reticular connective tissue, which forms the stroma or supporting framework of many soft organs
- also help form the basement membrane
Note that our classification scheme has two major subclasses of connective tissues: what are they? explain them.
- Embryonic connective tissues are present in the embryo, and in the fetus
- mature connective tissues, are present in the newborn.
Embryonic Connective Tissues: Mesenchyme. Location and function?
- under skin and along developing bones of embryo; some in adult connective tissue, especially along blood vessels
- Forms almost all other types of connective tissue.
Embryonic Connective Tissues: mucous connective tissue. Location and function?
- Umbilical cord of fetus.
- support
Mature Connective Tissues: Loose Connective Tissues- AREOLAR CONNECTIVE TISSUE. Location and function?
- everywhere
- Strength, elasticity, support
Mature Connective Tissues: Loose Connective Tissue- ADIPOSE TISSUE. Location and function?
- everywhere
- Reduces heat loss through skin; serves as an energy reserve; supports and protects organs.
Mature Connective Tissues: Loose Connective Tissue- RETICULAR CONNECTIVE TISSUE. Location and function?
- Stroma (supporting framework) of liver, spleen, lymph nodes; red bone marrow; reticular lamina of basement membrane; around blood vessels and muscles.
- Forms stroma of organs; binds smooth muscle tissue cells; filters and removes worn-out blood cells in spleen and microbes in lymph nodes
Mature Connective Tissues: Dense Connective Tissue- DENSE REGULAR CONNECTIVE TISSUE. Location and function?
- Forms tendons, most ligaments, and aponeuroses
- withstands pulling (tension) along long axis of fibers
Mature Connective Tissues: Dense Connective Tissue-DENSE IRREGULAR CONNECTIVE TISSUE. Location and function?
- occurs in sheets, region of dermis of skin, fibrous pericardium of heart, periosteum of bone, perichondrium of cartilage, joint capsules, membrane capsules around various organs; also in heart valves.
- Provides tensile (pulling) strength in many directions
Mature Connective Tissues: Dense Connective Tissue- ELASTIC CONNECTIVE TISSUE. Location and function?
- Lung tissue, walls of elastic arteries, trachea, bronchial tubes, true vocal cords, suspensory ligaments of penis, some ligaments between vertebrae.
- Allows stretching of various organs; is strong and can recoil to original shape after being stretched.
- Elasticity is important to normal functioning of lung tissue (recoils in exhaling) and elastic arteries
The five types of mature connective tissues are? Within each category, name each type.
(1) loose connective tissues
- areolar, adipose, reticular
(2) dense connective tissues
- dense regular, dense irregular, elastic
(3) cartilage
- hyaline, fibrocartilage, elastic
(4) bone tissue
- compact or spongy
(5) liquid connective tissue
- blood tissue and lymph
What are the two types of embryonic connective tissue?
Mesenchyme and mucous connective tissue
Mature Connective Tissues: Cartilage- HYALINE CARTILAGE. Location and function?
- ends of long bones, anterior ends of ribs, nose, parts of larynx, trachea, bronchi, bronchial tubes, embryonic and fetal skeleton.
- Provides smooth surfaces for movement at joints, flexibility, and support; weakest type of cartilage
Mature Connective Tissues: Cartilage- FIBROCARTILAGE. Location and function?
- Pubic symphysis (where hip bones join anteriorly), intervertebral discs, menisci (cartilage pads) of knee, portions of tendons that insert into cartilage.
- Support and joining structures together. Strength and rigidity make it the strongest type of cartilage
Mature Connective Tissues: Cartilage- ELASTIC CARTILAGE. Location and function?
- Lid on top of larynx (epiglottis), part of external ear (auricle), auditory (eustachian) tubes.
- Provides strength and elasticity; maintains shape of certain structures.
Bone tissue is classified as either___ or ____, depending on how its extracellular matrix and cells are organized.
compact or spongy
The basic unit of compact bone is an osteon or haversian system. Each system has four parts, name and explain them.
1) The lamellae are rings of extracellular matrix that consist of mineral salts, which give bone hardness and compressive strength, and collagen fibers, which give bone tensile strength.
2) Lacunae are small spaces between lamellae that contain mature bone cells called osteocytes.
3) Projecting from the lacunae are canaliculi which provide routes for nutrients to reach osteocytes and for wastes to leave them
4) A central (haversian) canal contains blood vessels and nerves.
Spongy bone lacks ___. Rather, it consists of columns of bone called_____, which contain lamellae, osteocytes, lacunae, and canaliculi. Spaces between ___ are filled with red bone marrow.
- osteons
- trabeculae, trabeculae
What is blood tissue?
- a connective tissue with a liquid extracellular matrix and formed elements.
- The extracellular matrix is called blood plasma.
- The blood plasma is a pale yellow fluid that consists mostly of water with a wide variety of dissolved substances
- Suspended in the blood plasma are formed elements—rbcs (transport O2 to body cells and remove C02 from them), wbcs (phagocytosis, immunity) and platelets (blood clotting)
What is lymph? Examples?
- extracellular fluid that flows in lymphatic vessels.
- connective tissue that consists of several types of cells in a clear liquid extracellular matrix
- The composition of lymph varies from one part of the body to another. For example, lymph leaving lymph nodes includes many lymphocytes, a type of white blood cell, in contrast to lymph from the small intestine, which has a high content of newly absorbed dietary lipids.
Membranes are flat sheets of pliable tissue that cover or line a part of the body. The majority of membranes consist of an____ layer and an underlying____ tissue layer and are called ____ membranes.
epithelial, connective, epithelial
Name the 3 main epithelial membranes of the body.
-mucous membranes, serous membranes, and the cutaneous membrane, or skin.
What does the mucous membrane do?
- lines a body cavity that opens directly to the exterior.
- line the entire digestive, respiratory, and reproductive tracts, and much of the urinary tract.
- consist of a lining layer of epithelium and an underlying layer of connective tissue
The connective tissue layer of a mucous membrane is areolar connective tissue and is called the ___ ____. It supports the epithelium, binds it to the underlying structures, allows some flexibility of the membrane, and affords some protection for underlying structures.
lamina propria
What does the serous membrane do?
- lines a body cavity that does not open directly to the exterior (thoracic or abdominal cavities), and it covers the organs that are within the cavity.
- consist of areolar connective tissue covered by mesothelium which secretes serous fluid, a watery lubricant that allows organs to glide easily
What does the cutaneous membrane (skin) do?
-covers the entire surface of the body and consists of a superficial portion called the epidermis and a deeper portion called the dermis
What does the synovial membrane do?
- line the cavities of freely movable joints (joint cavities).
- line structures that do not open to the exterior
- they lack an epithelium and are therefore not epithelial membranes.
- composed of a discontinuous layer of cells called synoviocytes which are closer to the synovial cavity, and a layer of connective tissue deep to the synoviocytes which secrete some of the components of synovial fluid.
- Synovial fluid lubricates and nourishes the cartilage covering the bones at movable joints
Skeletal muscle tissue. Description, Location and Function?
- Long, cylindrical, striated fibers
- Usually attached to bones by tendons
- Motion, posture, heat production, protection.
Cardiac muscle tissue. Description, Location and Function?
- Branched, striated fibers, intercalated discs which contain desmosomes and gap junctions
- Heart wall.
- Pumps blood to all parts of body.
Muscular tissues consist of elongated cells called muscle fibers or myocytes that can use ATP to generate force. As a result, muscular tissues produce body movements, maintain posture, and generate heat. They also provides protection. Based on their location and certain structural and functional features, muscular tissues are classified into three types: what are they?
skeletal, cardiac, and smooth
Smooth muscle tissue. Description, Location and Function?
- Fibers usually involuntary, nonstriated
- small spindle-shaped cell thickest in middle, tapering at each end, and containing a single, centrally located nucleus.
- Gap junctions connect many individual fibers in some smooth muscle tissues
- Iris of eyes; walls of hollow internal structures such as blood vessels, airways to lungs, stomach, intestines, gallbladder, urinary bladder, and uterus.
- Motion
Despite the awesome complexity of the nervous system, it consists of only two principal types of cells: ____ and ____.
neurons, neuroglia
What are neurons/nerve cells?
- convert stimuli into nerve action potentials
- consist of 3 basic parts: a cell body and two kinds of cell processes—dendrites and axons
- Dendrites are extensions that are the major receiving/input portion of a neuron.
- The axon is the output portion of a neuron, conducting nerve impulses toward another neuron or to some other tissue
Neurons and muscle fibers are considered____ cells because they exhibit electrical excitability, the ability to respond to certain stimuli by producing electrical signals such as action potentials.
excitable
When an action potential forms in a neuron, the neuron releases chemicals called _______, which allow neurons to communicate with other neurons, muscle fibers, or glands.
neurotransmitters
Tissue repair is the replacement of worn-out, damaged, or dead cells. New cells originate by cell division from the___, the supporting connective tissue, or from the ____ , cells that constitute the functioning part of the tissue or organ.
stroma, parenchyma
In adults, each of the four basic tissue types (epithelial, connective, muscle, and nervous) has a different capacity for replenishing parenchymal cells lost by damage, disease, or other processes. Epithelial cells, which endure considerable wear and tear (and even injury) in some locations, have a continuous capacity for renewal. In some cases, immature, undifferentiated cells called___ cells divide to replace lost or damaged cells.
stem
In adults, each of the four basic tissue types (epithelial, connective, muscle, and nervous) has a different capacity for replenishing parenchymal cells lost by damage, disease, or other processes. Which types have a continuous capacity for renewal and which do not?
- epithelial and connective can renew
- Muscular tissues have a relatively poor capacity for renewal of lost cells.
- Nervous tissue has the poorest capacity for renewal.
What is fibrosis?
- if fibroblasts of the stroma are active in the repair, the replacement tissue will be a new connective tissue.
- The fibroblasts synthesize collagen and other extracellular matrix materials that aggregate to form scar tissue, a process known as fibrosis.
