Tissue Level Of Organization Flashcards
What is a tissue?
Collections of cells and cell products that perform specific, limited functions.
What is histology?
Study of tissues
What is epithelium tissue?
- Covers exposed surfaces
- Lines internal passageways
- Forms glands
What is connective tissue?
- Supports other tissues
- Fills internal spaces
- No contract with the environment
What is muscle tissue?
- Specialized for contraction
- Skeletal, cardiac, and smooth muscles
What is neural tissue?
- Carried electrical signals from one part of the body to another
What are the five characteristics of epithelial tissue?
- Cellularity (Cell junctions)
- Polarity (Apical and basal surfaces)
- Attachment (Basement membrane)
- Avascularity (No blood vessels)
- Regeneration
What are the four functions of epithelial tissue?
- Physical protection
- Control permeability
- Sensation (Neuroepithelium)
- Secretions (Glandular epithelium)
How do you increase surface area?
- Microvilli increase absorption or secretion
- Cilia (ciliated epithelium) move fluids
What are the three ways the integrity of epithelial tissues are maintained?
- Intercellular connections
- Attachment to basement membrane
- Maintain and repair
How does intercellular connections work?
- Bonds between adjacent cells
- Support and communication
- Includes:
- Tight junctions
- Gap junctions
- Desmosomes:
- Belt
- Button (spot)
What is the basement membrane (basal lamina)?
- It has two layers:
- Lamina lucida- Thin layer
- Produced by epithelium
- Lamina densa - Thick fibers
- Produced by connective tissue
- Attachment of epithelial cells to basal lamina:
- Hemidesmosomes
How are epithelial cells maintained and repaired?
They are replaced by division of germinative (stem) cells near the basal lamina.
What are the two classes of epithelial tissues?
- Epithelia: (AKA surface epithelium)
- Layers of cells covering external or lining internal surfaces. - Glands:
- Structures that produce secretions
What are the two classes of surface epithelium?
- Cell shape
- Squamous epithelia: flat shaped
- Cuboidal epithelia: square shaped
- Columnar epithelia: tall shaped - Layers
- Simple epithelium: single layer of cells
- Stratified epithelium: several layers of cells
What are the two types of squamous epithelium?
- Simple squamous epithelium
- Most delicate epithelium: diffusion and absorption
- Mesothelium- endothelium- lung alveoli - Stratified squamous epithelium
- Toughest type of epithelium: physical protection
- Skin- lining of mouth, esophagus, rectum, vagina…
What are the three types of cuboidal epithelium?
- Simple cuboidal epithelium
- Absorption and secretion
- Renal tubules- thyroid gland - Stratified cuboidal epithelium
- Protection, absorption, and secretion
- Sweat and mammary gland ducts - Transitional epithelium
- Stretch and recoil
- Urinary bladder- uterus
What are the three types of columnar epithelium?
- Simple columnar epithelium
- Absorption and secretion
- Stomach- intestine- uterine tubes - Stratified columnar epithelium
- Protection
- Salivary gland ducts - Pseudostratified columnar epithelium
- Protection, secretion, and cilia movement
- Trachea- bronchi
What are the two types of glandular epithelium?
- Endocrine glands
- No ducts (ductless glands)
- Release hormones into interstitial fluid —> blood
- e.g thyroid gland- adrenal gland… - Exocrine glands
- Have ducts
- Produce secretions —> ducts —> epithelial surfaces
- e.g sweat glands
- Modes of secretion
What are the modes secretion? (Crine)
Modes of secretion:
- Merocrine secretion
- Released by vesicles (exocytosis)
- e.g sweat glands- salivary glands
- Apocrine secretion
- Released by shedding cytoplasm
- e.g mammary gland
- Holocrine secretion
- Released by cells bursting
- Gland cells are replaced by stem cells
- e.g sebaceous gland
What are the three types of exocrine glands?
Serous glands:
watery secretions
e.g., parotid salivary gland
Mucous glands:
secrete mucins
e.g., sublingual salivary gland
Mixed exocrine glands:
both serous and mucous
e.g., submandibular salivary gland
What is the structure of exocrine glands?
Unicellular
Multicellular
What is the unicellular exocrine gland?
Goblet cells:
the only unicellular exocrine gland
scattered among epithelia:
e.g., in intestinal lining
secrete mucin
What are multicellular exocrine glands?
Structure of the duct:
simple (undivided)
compound (divided)
Shape of secretory portion:
tubular (tube shaped)
alveolar/acinar (blind pocket/chamber)
tubuloalveolar/tubuloacinar
Relationship between ducts and glands:
branched (several secretory areas sharing 1 duct)
What is an example of a coiled tubular gland?
Merocrine sweat glands
What is an example of simple branched alveolar glands?
Sebaceous (oil) glands
What is an example of a compound tubular?
Testes (somniferous tubules)
What is an example of compound alveolar (acinar)?
Mammary glands
What is an example of compound tubuloalveolar?
Salivary glands
Pancreas
What are the four functions of connective tissues?
- Connect epithelium to the rest of the body
- Provide structure
- Store energy
- Transport materials
What are the components (2) of connective tissues?
Specialized cells
Extracellular matrix (most of the tissue volume:
(Fibres and ground substance)
- solid: protein fibers
- fluid: ground substance
What are the three classifications of connective tissues?
Connective tissue proper:
connect and protect (fat & tendons)
Fluid connective tissues:
transport (blood & lymph)
Supportive connective tissues:
structural strength (cartilage & bone)
What is in the connective tissue proper’s matrix?
Fibers and ground stubstance
What are the permanent residents in connective tissue proper?
- Fibroblasts (most abundant most important)
- Adipocytes
- Mesnchymal cells
- Melanocytes
What are the migratory substances in connective tissue proper?
- Lymphocytes
- Macrophages
- Microphages
- Mast cells
What are fibroblasts? (Proper CT)
Most abundant cell type.
Found in all connective tissue proper.
Secrets proteins (tubers) and hyaluronan (cellular cement).
(permanent residents)