Ch. 4 Tissue Level of Organization Flashcards
What are the 4 main types of tissues?
Epithelial, connective, muscular, nervous
What are the 3 functions of cell junctions?
- Anchor cells together ot to extracellular material (adherens junctions, desmosomes, hemidesmosomes)
- Fluid-tight seals bt cells (tight junctions)
- Channels to allow ions/molec to pass from cell to cell (gap junctions)
Compare and contrast adherens junctions and desmosomes
ADHERENS - transmembrane prot attached to microfilaments (cytoskeleton); join epithelial cells tgt
DESMOS - transmembrane prot are attached to intermediate filaments (keratin, cytoskeleton); prevent separation due to stretching
What are hemidesmosomes?
Transmembrane prot attached to intermediate filaments; attaches deepest E cells to basal lamina
How do the function of tight junctions relate to its structure?
Its function is to prevent passage of substances (including H2O); can be found bt cells lining GI tract, bladder
- 2 plasma membranes are tightly bound via interlocking membrane prot
How are gap junctions formed?
Formed by connexins (channel proteins) to allow cells to communicate
What are the main purposes of epithelial tissue?
- Covers and lines surfaces, provides selective barriers (bt body and env; bt different structures) for movement of material; provides protection from damage; absorbs nutrients
- Forms secreting portions of glands
Describe the structure of epithelial tissue
- Closely packed sheets of cells
- Sit on basement membrane
- High rate of cell regeneration
- Has its own nerve supply
- Avascular; obtains blood supply from blood vessels within C tissues via diffusion
Basic features of epithelial cells
- Microvilli to increase SA in digestive, urinary, and repro tracts
- Cilia found in resp and repro tracts
- Apical surface exposed to space or env. inside organ or tube (lumen)
- Basal surface attaches to underlying E cells or deeper tissues
Types of epithelia
Simple squamous (material exchange) Stratified squamous (protection) Simple cuboidal (secretion, absorption) Stratified cuboidal Simple columnar (sec, absorp) Stratified columnar Pseudostratified columnar (protection)
How does structure of simple squamous E relate to its function?
- single layer of flat cells; thin layer allows for diffusion and filtration
- diffusion occurs in lungs, filtration in kidneys
- endothelium lines blood V, endocardium - heart chambers, mesothelium - serous membranes (pleura, pericardium, peritoneum)
Stratified squamous E - non-keratinzed
- two or more cell layers; apical cells are flat
- because it is non-keratinized (keratin is a strong prot!), its purpose isnt strength but still protection
- lines moist surfaces (mouth, esophagus, vagina)
Stratified squamous E - keratinized
- two or more cell layers; apical cells are flat
- keratinized –> strength!! as keratin is a tough, fibrous intercellular prot
- on superficial layer of skin
Simple cuboidal E
- one layer of cube shape cells (nucleus appears round)
- absorption or secretion (lines kidney tubules, thyroid gland)
Stratified cuboidal E
- 2 or more layers; apical cells are cube-shaped
- found in some ducts (sweat gland ducts, male urethra, esophageal gland ducts)
Simple columnar E - nonciliated
- single layer of column-shaped cells (oval nuclei near base of cells)
- contains microvilli at apical surface and goblet cells
- absorption and secretion (mucus secretion to lubricate GI, respiratory, repro, urinary systems)
Simple columnar E - ciliated
- cilia on apical surface
- move fluid, mucus, and foreign particles
- contain Goblet cells (specialized for producing mucus)
- lines bronchioles, uterine tubes, paranasal sinuses
Pseudostratified columnar E - nonciliated
- single layer of columnar cells
- appears layered bc nuclei are at different levels
- all attached to basement membrane; not all reach apical layer
- lacks Goblet cells
- lines epididymis, ducts of larger glands, parts of male urethra
- absorption and secretion
Pseudostratified columnar E - ciliated
- contains Goblet cells
- lines airways of upper resp tract
- removes pathogens, debris, dust
- secrete mucous; moisten
Stratified columnar E
- apical layer has column-shaped cells
- lines part of urethra, esophageal and salivary gland ducts
- protection and secretion
Transitional epithelium (relaxed and stretched states)
R - large and round apical cells, looks like strat cub ep
S - looks like strat sq ep
- lines urinary bladder, portions of ureters + urethra
Glandular epithelium - exocrine
- secretes a product onto free surface of epithelial layer, connected by ducts
(e. g. Goblet cells secrete mucous, sweat/oil/salivary glands)
Glandular epithelium - endocrine
- secretes hormones into interstitial fluid, bloodstream; no ducts
(e. g. pituitary, thyroid, adrenal glands
Which glands have both exocrine and endocrine tissues?
pancreas, ovaries, testes
2 structural classifications of exocrine glands
- Unicellular glands - Goblet cells
2. Multicellular glands - form distinct microscopic structure, sweat glands, oil glands, salivary glands
3 functional classification of exocrine glands
- Merocrine: discharge secretory product via exocytosis (e.g. salivary gland)
- Aprocrine: accumulate sec products at apical surface; apical portion of cell pinches off; remaining part of cell repairs itself and process repeats (e.g. mammary glands)
- Holocrine: cells accumulate products, die + rupture to release products (e.g. sebaceous glands)
What is connective tissue made of?
- Cells scattered in an extra-cellular matrix
- Matrix composed of protein fibers and ground substance
- Good nerve and blood supply, except in cartilage and tendons
What are the 2 types of constituent cells?
- blast: immature cells that can divide and produce matrix
- cyte: mature cells that can’t divide or produce matrix; maintain tissue and matrix
What are fibroblasts?
- secrete fibers and ground substance
- large, flat cells
What are macrophages?
Immune cells!
- develop from monocytes (circulate in blood)
- engulf bact and debris by phagocytosis
What are plasma cells?
- develop from B lymphocytes
- produce antibodies that fight against foreign substances
What are the 7 constituent cell types in CT?
- Fibroblasts
- Macrophages
- Plasma cells
- Neutrophils (leukocyte)
- Eosinophils (leukocyte)
- Mast cells
- Adipocytes
How do neutrophils and eosinophils differ?
N - migrate to sites of bact invasion/infections
E - migrate to sites of parasitic invasion
- both contain toxic molec, enz
Where are mast cells found and what do they produce?
Found along blood vessels inc T, produce histamine that dilates small BV
What is the function of adipocytes?
Fat storage and protection
- found subcutaneously (underneath skin) and around organs
What are the 3 types of fibers in the ECM?
- Collagen fibers
- Reticular fibers
- Elastic fibers
What is the structure of collagen fibers and where are they found?
Strong and flexible; in parallel bundles; bone, cartilage, tendons, ligaments
How do the structure of reticular fibers relate to its function?
Fine bundles of collagen fibers with a coating of glycoprotein allow support for BV and soft organs (e.g. spleen, lymph nodes)
*form part of basement membrane!
What is the form of elastic fibers and where are they found?
Made of elastin surrounded by fibrillin; form network of fibers; found in lungs, blood, vessels, skin
What is the structure & function of ground substance?
Fluid, semifluid gelatinous, or calcified material bt cells and fibers; contain water and large combinations of prot and polysach
Supports cells, holds cells tgt, stores water, allow transport of molec and chem rxns
What are the types of connective tissue?
loose, dense, cartilage, bone, blood
What are the types of loose CT?
areolar, adipose, reticular
What are the types of dense CT?
regular, irregular, elastic
What are the types of cartilage CT?
hyaline, fibro, elastic
What are areolar CT composed of and what is its function? Where are they found?
Fibers (collagen, elastic, reticular), cells (fib, adip, WBC), gelatinous ground substance
Strength, elasticity, support
Found in subcutaneous layer + dermis of skin, around BV, nerves, organs
What is the function of adipose CT?
- contains adipocytes, derived from fibroblasts
- reduce heat loss, energy reserve, supports and protects organs (e.g. endocrine organs)
- specialized for triglyceride (fat) storage; nucleus & cytoplasm pushed to cell periphery
What is the structure and function of reticular CT?
Network of reticular fibers + cells that form a framework (stroma) of organs
Ties cells of smooth muscle together and support soft organs (e.g. liver, spleen, lymph nodes, bone marrow)
Act as filters in spleen and lymph nodes
How do dense CT differ from loose CT in terms of fibers and cells?
Dense CT has more numerous, thicker, denser fibers but fewer cells
What are dense regular CT composed of and where are they found?
- Collagen fibers in parallel bundles, fibroblasts cells in bt
- Forms tendons ligaments, provides tensile strength in one direction
**tissue does not heal quickly bc collagen is not living
How does dense irregular CT differ from regular CT?
- irregularly arranged, few fibroblasts in bt; often occurs in sheets (fasciae)
- tissue resists tension from ANY direction
- found in tough tissues (e.g. membranes surrounding heart, cartilage, bones)
What is the structure and function of elastic CT?
- elastic fibers with fibroblasts in bt
- can stretch and return to original shape; flexibility
- found in lung tissue, vocal cords, intervertebral ligaments, BV
What are distinct properties of cartilage CT?
- dense network of collagen + elastic fibers embedded in chondroitin sulfate (rubbery matrix)
- collagen provides strength; C.S. provides resilience
- stronger than dense CT
- only avascular CT; secretes anti-angiogenesis factors
- surrounded by perichondrium
What are cartilage produced by?
Chondroblasts; mature cartilage contains chrondrocytes
Structure and function of hyaline C?
- Thin, weak collagen fibers
- many chondrocytes in lacunae (little lakes) surrounded by perichondrium
- ground substance is a resilient gel
- reduces friction + absorbs shock at joints
Structure and function of fibrocartilage? Where are they found?
- more collagen fibers –> rigidity; strongest type
- chondrocytes scattered, thick bundles o fibers
- lacks perichondrium
found in pubic symphysis, menisci of knee
Structure and function of elastic C?
- chondrocytes in threadlike network of elastic fibers
- perichondrium present
- shape + elasticity (after deformations
- found in ear, nose, vocal, cartilages, epiglottis
What are bone tissue comprised of?
- mineralized/solid ECM
- hardness due to calcium and phosphate
- strength due to interwoven collagen fibers
- lacunae contain osteocytes
- compact or spongy
Describe the blood’s matrix and its function
- liquid matrix (blood plasma) made of erythrocytes, leukocytes, platelets
- found within BV, heart chambers
- clotting, immune functions, transport of O2//CO2, nutrients, wastes
What are membranes?
flat sheets of pliable tissue that line a part of the body
How do epithelial and synovial membranes differ?
E - epithelial layer + underlying CT layer; mucous, serous, cutaneous
S - no epithelium + contain CT; in joints
What do mucous membranes line?
body cavities that open directly onto exterior (e.g. digestive, resp, repro, urinary tracts)
How are mucous membranes made of and how do they function?
- epithelium underlined with areolar CT + Goblet cells
- G cells secrete mucus onto surface; lubricate/trap pathogens
What do serous membranes?
body cavities that do not open to exterior (e.g. abdominal, thoracic cavities)
What are serous membranes made of?
Parietal and visceral layers w serous fluid in bt (pleura, pericardium, peritoneum)
Consists of mesothelium (simple sq E) underlined with areolar CT
What are cutaneous membranes?
Skin !! –> line outside of the body
Consists of dermis and epidermis (keratinized strat squa E)
What are the structure and functions of synovial membranes?
line movable joints, contain CT but no E
produce synovial fluid to lubricate joints; discontinuous layer of synoviocytes
What do muscular tissues comprise of?
muscle fibers (myocytes)
each cell contains actin and myosin (which are contractile proteins)
What are the 3 types of muscular tissues?
skeletal, cardiac, smooth
Structure and function of skeletal MT?
long, cylindrical, striated fibers (cells) with many peripheral nuclei
- attached to bones by tendons
- voluntary contraction/relaxation; conscious control –> motion, posture, heat prod, protection
Structure and function of cardiac MT?
branched, striated cylinders, with ONE central nucleus
- forms heart wall; pumps blood to all parts of body
- involuntary control (under ANS)
What are intercalated discs?
thickenings of plasma membrane that contain gap junctions and desmosomes
Structure and function of smooth muscle?
Spindle-shaped cells w single central nucleus, lack striations; cells connect via gap junctions
Involuntary contraction/relaxation
Found in walls of hollow organs (BV, GI tract, bladder)
What are the 2 main cell types in nervous tissue and how do they differ?
- NEURONS - functional, conduct electrical impulses
2. NEUROGLIAL CELLS - supportive cells, insulate axons for faster conduction, nourish + regulate neuronal function
Functions of CNS and PNS?
Senses stimuli and converts into action potentials; conducts nerve impulses to neurons/muscle fibres/ glands; maintain homeostasis
