Chapter 4: Tissues Flashcards
Tissues
Are groups of cells that are similar in structure and perform a common or related function
Nervous Tissue
- Internal communication
- “controls”
- Include brain, spinal cord, nerves
Muscle Tissue
- -Contracts to cause movement
- “moves”
- Include muscles attached to bones (skeletal), muscles of heart (cardiac), muscles of walls of hollowed organs (smooth)
Epithelial Tissue
-Forms boundaries between different environments, protects, secretes, absorbs, filters,
-“covers”
-Include lining of digestive tract organs and other hollow organs, glands (e.g pancreas), skin surface (epidermis)
Functions:
-protection
-absorption
-filtration
-excretion
-secretion
-sensory reception
Connective tissue
supports protects, binds, other tissues together
- “supports”
- Include bones, tendons, fat and other soft padding tissue
Epithelial tissue
- A sheet of cells that covers a body surface or lines a body cavity
- 2 forms occur in the body
- covering and lining epithelium
- glandular epithelium
-high regenerative capacity
covering and lining epithelium
forms the outer layer of the skin
- dips into and lines the open cavities of the urogenital, digestive, and respiratory systems
- covers the walls and organs of the closed ventral body cavity
glandular epithelium
-fashions the glands of the body
Epithelium- Apical surface
Is not attached to surrounding tissue and is exposed to either the outside of the body or the cavity of an internal organ
- borders open space
- have microvilli, fingerlike extensions of the plasma membrane (increase the exposed surface area)
- “surface”
Epithelium- Basal surface
Attached to the underlying connective tissue
-Thin, supporting sheet basal lamina. This noncellular adhesive sheet consists of glycoproteins secreted by the epithelial cells plus some fine collagen fibers. acts as a selective filter that determines what can enter the epithelium. Also acts as scaffolding along which epithelial cells can migrate to repair a wound
“inside”
Epithelium- Specialized contacts
except for glandular epithelia, epithelial cells fit closely together to form continuous sheets
-the sides of adjacent cells are tied together by tight junctions and desmosomes.
- tight junctions prevent substances from leaking through spaces between cells.
- desmosomes keep cells from pulling apart
All epithelial sheets rest upon and are supported by connective tissue
true
Epithelium- Basement membrane
In between epithelial and connective tissue is basement membrane.
- reinforces the epithelial sheet, helps it resist stretching and tearing, and defines the epithelial boundary
- consists of 2 layers:
- basal lamina
- reticular lamina
-reticular lamina is deep to the basal lamina. consists of collagen protein fibers that “belongs to” the underlying connective tissue
epithelium is avascular (contains no blood vessels) but instead it is innervated (supplied by nerve fibers)
true
The epithelium is nourished by substances diffusing from blood vessels in the underlying connective tissue
Simple epithelia
consists of a single cell layer. typically found where absorption, secretion, and filtration occur
stratified epithelia
composed of 2 or more cell layers stacked on top of each other
-common in high abrasion areas where protection is important such as the skin surface and lining of the mouth
Squamous cells
flattened and scale-like
cuboidal cells
box-like, approx as tall as they are wide
columnar cells
are tall and column shaped
Epithelium- the shape of the nucleus conforms to that of the cell
true. example, squamous cell nucleus-flattened disc
colmnar cell nucleus-elongated
Simple squamous epithelia- endothelium
- “inner covering”
- provides a slick, friction-reducing lining in lymphatic vessels and in hollow organs of the cardiovascular system
- capillaries consist exclusively of endothelium
Simple squamous epithelia- mesothelium
- “middle covering”
- epithelium found in serous membranes , the membranes lining the ventral body cavity and covering its organs
Transitional epithelium
glandular epithelia
- secretion is an active process
- glands are classified according to 2 sets of traits
- where they release their product-glands may be endocrine “internally secreting” or exocrine “externally secreting”
*number of cells-glands may be unicellular or multicellular
multicellular epithelial glands form by invagination (inward growth) of an epithelial sheet
true
exocrine glands (epithelium) retain the connecting cells, which form a duct that transports secretions to the epithelial surface
true
endocrine glands lose their ducts during development (epithelium) they secrete hormones into the interstitial fluid. these hormones then enter the blood
true
Simple Squamous Epithelium
Description: Single layer of flattened cells
Function: Allows passage of materials by diffusion and filtration
Location: Air sacs of lungs, blood vessels, kidney glomeruli
Simple cuboidal epithelium
Description: single layer of cubelike cells
Function: secretion and absorption
Location: kidney tubules, ducts of small glands
Simple columnar epithelium
Description: single layer of tall cells, some with cilia, may contain goblet cells
Function: absorption; secretion of mucus, ciliated type propels mucus
Location: nonciliated type lines most of digestive tract, ciliated variety lines small bronchi, uterine tubes
Pseudostratified Columnar Epithelium
Description: single layer of cells of differing heights, may contain mucus secreting cells and bear cilia
Function: secretion of mucus
Location: nonciliated type in male’s sperm- carrying ducts, ciliated type lines trachea and upper respiratory tract
Because of different heights gives impression of 2 layers when actually just 1
Stratified Squamous Epithelium
Description Thick membrane of several cell layers Surfaced cells are flattened; in the keratinized type, the surface cells are dead, basal cells are active
Function Protection
Location Keratinized type forms epidermis; non- keratinzed type forms moist linings of esophagus, mouth & vagina
Stratified Cuboidal
Quite rare in body
Found in some sweat and mammary glands
Typically two cell layers thick
Stratified Columnar
Limited distribution in body
Small amounts in pharynx, male urethra, and lining some glandular ducts (mammary glands)
Also occurs at transition areas between two other types of epithelia
Transitional Epithelium
Description: Resembles both stratified squamous and stratified cuboidal; basal cells cuboidal or columnar; surface cells squamouslike
Function: stretches readily & permits distension of urinary organ
Location: lines ureters and bladder
Glandular Epithelia
A gland is one or more cells that makes and secretes an aqueous fluid
Classified by:
-Site of product release—endocrine or exocrine
-Relative number of cells forming the gland—unicellular (e.g., goblet cells) or multicellular
Unicellular exocrine glands
The only important unicellular gland is the goblet cell
Produce mucin -> mucus
Secreted by exocytosis
Multicellular exocrine glands
Multicellular exocrine glands are composed of a duct and a secretory unit
Classified according to structure: Duct type (simple or compound) Structure of their secretory units (tubular, alveolar, or tubuloalveolar)
Simple duct structure (duct does not branch)/ Tubular
secretory structure
- Simple tubular (example: intestinal glands)
- Simple branched tubular (example: stomach gastric glands)
Compound duct structure (duct branches)/ Tubular
secretory structure
-Compound tubular (example: duodenal glands of small intestine)
Simple duct structure (duct does not branch)/Alveolar secretory structure
- Simple alveolar (example: none)
- Simple branched alveolar (example: sebaceous oil glands
Compound duct structure (duct branches)/ Alveolar secretory structure
- Compound alveolar (example: mammary glands)
- Compound tubuloalveolar (example: salivary glands)
Modes of secretion
- Merocrine (merely secrete): products are secreted by exocytosis (e.g. pancreas, sweat, and salivary glands)
- Holocrine: Products are secreted by rupture of gland cells (e.g., sebaceous glands aka acne)
- Apocrine: pinches off secretion & repairs, controversial if found in humans (mammary)
Connective tissue
Most abundant and widely distributed tissue type
Four classes:
- Connective tissue proper
* Loose (areolar, adipose, reticular)
* Dense (regular, irregular, elastic) - Cartilage
Hyaline, elastic, fibrocartilage - Bone tissue
- Blood
Functions of connective tissues:
-Provide a structural framework for the body
- Transport fluids and dissolved materials
- Protection of delicate organs
- Supporting, surrounding, interconnecting other types of tissue
- Storing energy reserves, especially triglycerides
- Defense against invading microorganisms
Characteristics of connective tissues
- Extracellular matrix:
- ground substance
- fibers
- cells
- common origin of mesenchyme
**varying degrees of vascularity
Structural elements of connective tissue- Ground substance
Components:
*Interstitial fluid
*Adhesion proteins (“glue”)
*Proteoglycans
--Trap water in varying
amounts, affecting
the viscosity of the
ground substance3 types of fibers of connective tissue
A.) Collagen (white fibers):
Strongest and most abundant type
High tensile strength
b) Elastic (yellow fibers):
Stretch and recoil
c) Reticular:
Short, fine, highly branched collagenous fibers
Structural elements of connective tissue- cells
Mitotically active and secretory cells = “blasts” *Fibroblasts in connective tissue proper *Chondroblasts in cartilage *Osteoblasts in bone
Mature cells = “cytes”
*Chondrocytes in cartilage
*Osteocytes in bone
*Erythrocytes in blood
*Fat cells (adipocytes),
white blood cells
(leukocytes), mast cells,
and macrophages
Connective tissue proper
Loose connective tissue:
- areolar
- adipose
- reticular
Dense connective tissue:
- dense regular
- dense irregular
- elastic
Areolar loose connective tissue
Description: Gel-like matrix with all three fiber types cells: fibroblasts, macrophages, mast cells, and some WBC
Function: Wraps and cushions organs; important role in inflammation; holds tissue fluids
Location: Under epithelium, packages organs, surrounds capillaries, most abundant
When body is inflamed, this tissue soaks up extra fluid like a sponge-edema
Adipose loose connective tissue
Description: 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
Location: Under skin in the hypodermis; around kidneys and eyeballs; within abdomen; in breasts
Reticular loose connective tissue
Description: Only reticular fibers in a typical loose ground substance; reticular cells lie on the network.
Function: Fibers form a soft internal skeleton (stroma) that supports free blood cells, mostly lymphocytes
Location: Lymphoid organs (lymph nodes, bone marrow, and spleen).
Regular dense connective tissuee
Description: Primarily parallel collagen fibers; a few elastic fibers; major cell type is the fibroblast.
Function: Attaches muscles to bones; attaches bone to bones withstands great tensile stress
Location: Tendons, most ligaments, aponeuroses
(sheet like tendinous material).
Irregular dense connective tissue
Description: Primarily irregularly arranged collagen fibers; some elastic fibers; major cell type is the fibroblast.
Function: Able to withstand tension exerted in many directions; provides structural strength.
Location: Fibrous capsules of organs and of joints; dermis of the skin; submucosa of the digestive tract.
Elastic dense connective tissue
Description: Dense regular connective tissue containing a high proportion of elastic fibers.
Function: Allows recoil of tissue following 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 walls of the bronchial tubes.
Cartilage
3 types of cartilage:
- Hyaline cartilage
- elastic cartilage
- fibrocartilage
- Cartilage is avascular (no blood vessels)
- Aging cartilage loses ability to divide
Hyaline cartilage
Description: collagen fibers form an imperceptible network; chondrocytes lie in lacunae
Function: Supports and reinforces; has resilient cushioning properties; resists compressive stress
Location: covers ends of long bones; forms costal cartilage of ribs; cartilage of nose, trachea and larynx
Epiphyseal plates (growth plates)
cartilage which turns into bone
Elastic cartilage
Description: Similar to hyaline cartilage, but more elastic fibers in matrix.
Function: Maintains the shape of a structure while allowing great flexibility.
Location: Supports the external ear (pinna); epiglottis.
Fibrocartilage
Description: Matrix similar to but less firm than that in hyaline cartilage; thick collagen fibers predominate.
Function:Tensile strength with the ability to absorb compressive shock.
Location: Intervertebral discs; pubic symphysis; discs of knee joint.
Osseous Bone
Description: hard calcified matrix containing collagen; well vascularized; osteocytes lie in lacunae
Function: bone supports and protects, provides levers for muscles; stores minerals; marrow inside bones is site of blood cell formation
Location: bones
High regeneration
Marfan’s syndrome
A genetic disorder of the connective tissue (long bones, sternal indent, scoliosis, CV problems)
Blood
Description: Red and white blood cells in a fluid matrix (plasma).
Function: Transport of respiratory gases, nutrients, wastes, and other substances.
Location: Contained within blood vessels.
Neural tissue
Specialized to conduct electrical impulses throughout the body
Contains two basic cell types: neurons and neuroglia (supporting cells)
Neurons: longest cells in body (up to 1 meter)
Most cannot divide: limited ability to repair
Neuron has large cell body, dendrites and axon
Skeletal muscle tissue
Moves the body by pulling on bones of the skeleton, making it possible for us to walk, dance, etc
Cardiac muscle tissue
Contraction moves blood through the blood vessels
Smooth muscle tissue
contractions move fluids and solids along the digestive tract and regulates the diameters of small arteries, among other functions
Epithelial membranes
- Cutaneous membrane (skin) (More detail with the Integumentary System, Chapter 5)
- Mucous membranes
Line body cavities open to the exterior (e.g., digestive and respiratory tracts) - Serous membranes
Parietal serosae line internal body walls
Visceral serosae cover internal organs
