tissues Flashcards
group of cells that usually have a common origin in an embryo
-function together carry out specialized activities
Tissue –
composed mostly of cells with little extracellular material tightly packed together
- arranged in sheets and attached to a basement membrane
- avascular (not supplied by blood capillaries) and is nourished by diffusion from the capillaries of underlying connective tissues
Epithelial tissues –
– lines blood vessels and air sacs of lungs; cardiovascular and lymphatic system
- permits exchange of nutrients, wastes, and gases (O2 and CO2)
- flat, thin and scale-like; allows for rapid passage of substances through them
- function: diffusion
Simple squamous
– lines kidney tubules and glands
- function: secretes and reabsorbs water and small molecules
- cubelike; may have microvilli at the apical (free) surface
- role of microvilli: increase surface area for absorption
Simple cuboidal
- lines most digestive organs and the gallbladder
- absorbs nutrients and produces mucus
- contains columnar epithelial cells with microvilli and goblet cells
Simple columnar
– appears to have 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 its basement membrane
- pseudo because of varying positions of cells
- clue: all components are attached to a common basement membrane
Pseudostratified epithelium
outer layer of skin (epidermis), mouth, vagina
-protects against absorption, drying out (desiccation), infection
stratified squamous
lines ducts of sweat glands and male urethra
- secretes water and ions
- 2 or more layers
Stratified cuboidal
lines epididymis, mammary glands, larynx
- secretes mucus
- part of the conjunctiva (thinnest skin) of the eye
Stratified columnar
– appearance is variable
- cells change shape from squamous to cuboidal and back (like the urinary bladder)
- depends on the organ
- role of cilia: aid secretion and absorption of whatever substance
• Transitional Epithelium
space/central part of cuboidal cells
Lumen –
– unicellular gland, epithelial cell; its secretion is mucus (sole function) to protect the organ from cell digestion
-look like empty sac-like structures
Goblet cell
forms brush border
microvilli
– lines the tracheal airway
- not a true stratified tissue
- mucus produced by goblet cell traps dust and other debris, and the cilia propel the mucus upward and away from the lungs
- Location: lining of nasal cavity, nasal sinuses, pharynx, auditory tubes, bronchi of the lungs
- “respiratory epithelium”
- function: secretes mucus and moves mucus and debris
Pseudostratified Ciliated Columnar Epithelium
- highly specialized to contract or shorten, to produce movement
- muscle cells are elongated to provide a long axis for contraction hence, they are called muscle fibers
MUSCLE TISSUE
- Excitability – ability to respond to stimuli
- Contractility - ability to shorten forcefully
- Extensibility – ability to stretch
- Elasticity - ability to resume resting length after contraction
- Tonicity - ability to maintain steady state of partial contraction
properties of muscle tissue
contractile elements
- basic structural and functional unit of skeletal muscle
- segment between Z disks
sarcomere
- receives stimuli from environment or from different organs
- transmits impulses to brain and spinal cord
- bring appropriate motor responses
nervous tissue
properties of nervous tissue
irritability and conductivity
elements of nervous tissue
neurons
neuroglia
parts of neuron
cell body soma cyton perikaryon
processes
type of neuron many processes -many dendrites one axon -starlike; fish eye -seen in the brain and spinal cord
multipolar
type of neuron two processes -1 axon, 1 dendrite -sensory neurons of eyes, nose, ears -spindle shaped appearance of nerve cell
bipolar
type of neuron – 1 process -only one axon -will branch and act as dendrite, the other as axon -owl’s eye
unipolar
- mainly composed of extracellular matrix of ground substance and protein fibers
- highly vascular except for cartilage, tendons, and ligaments
- consist of 2 basic elements: extracellular matrix (protein fibers and ground substance) and cells
- cells are derived primarily from mesenchymal cells
Connective Tissues
- large, flat cells with branching processes
- secrete extracellular matrix
- true connective tissue cells
fibroblasts
– large, irregular –shaped with short blunt cytoplasmic processes
- develop from monocytes (a WBC type)
- capable of engulfing bacteria and cellular debris
- capable of phagocytosis; have pseudopods for engulfing
Macrophages
– many granules
- abundant basophilic cytoplasmic granules which obscure the nucleus
- produce histamine, chemical that dilates small blood vessels as part of inflammatory response
- can bind, ingest, kill bacteria
Mast cells
have signet ring appearance; nucleus is on the side (like the ‘pendant’ of a ring)
-specialized for fat storage
adipocytes
cart-wheel or wall clock appearance
- develop from a type of WBC called B lymphocytes
- have characteristic clock face or cart wheel appearance around the nuclear envelope
- principle produces of antibodies
Plasma cells –
not found in significant numbers
-migrate from blood into connective tissue in response to infection
WBC
- Component of umbilical cord (stem cells)
- Transient type that appears in normal development and differentiation of CT
- Consists of fibroblasts and collagen fibers with processes that appears to fuse with others
- Intercellular substance is abundant
- Soft, jelly-like and homogenous in fresh ppt
- Contains granular and fibrillar ppts when fixed
- Classic object of study is Wharton’s jelly of the umbilical cord
Mucuous CT
– has many spaces called areola
- most widely distributed
- soft, pliable tissue that cushions and protects the body organs it wraps
- fluid matrix contains cell types of fibers
- contains innumerable spaces called areola that provide reservoir of water and salts for surrounding tissues (for emergency)
- when a body region is inflamed, the areolar tissue in the area soaks up the excess fluid like a sponge, and the area swells and becomes puffy, a condition called edema
- looks like a tissue paper, used to see CT
• Areolar CT
- ground substance is fluid & relatively scanty due to abundant fat cells
- large fat cells are closely packed into fat lobules
- large size of fat cell is due to the presence of lymphoid organs (tissue, appendix, spleen)
• Adipose CT
dark brown to black
- forms the framework or CT ______ of bone marrow, lymphoid organs and endocrine glands
- together with phagocytes of other tissue is collectively known as reticulo-endothelial –macrophage system
- concerned with defense system of the body
- consists of network of reticular fibers and cells
• Reticular CT –
differs from loose mainly in great abundance of fibers
dense CT
messy arrangement of fibers
- seen in those organs pulled in many directions
- skin, periosteum of bone, perichondrium of cartilage
- bottom skin of frog
• Dense Irregular CT –
Dense, firm but pliable
Has cells (chondrocytes – uniqueness: cavities), fibers (collagens and elastic fibers) and ground substance (chondromucoprotein)
Lacunae – cavities where chondrocytes are housed
Some enveloped by a fibrous tissue sheath called perichondrium
No nerve nor blood supply of its own (avascular) and lacks lymphatic
cartilage
• – with perichondrium, invisible fibers
- function: provide smooth surface for movement of joints, flexibility and support
- matrix is homogenous, clear and glasslike because matrix and the collagenous fiber have the same refractive index
- chondrocytes located in lacuna
- cells may be in singles or in groups called cell nest or isogenous group
- location: trachea, anterior ends of ribs, growing ends of limbs, pharynx
Hyaline
with perichondrium; branching fine fibers
- greater opacity, flexibility, elasticity
- permeated in all directions by branching elastic fibers
- location: external ears, auditory tubes, epiglottis
Elastic
