Chapter 5 -Tissues Flashcards
What are the four primary tissue types
- epithelial – covers and lines
- connective – provides support
- muscle – enables movement
- nervous – controls work
What is histology
the study of the microscopic structures of tissues and organs.
List seven functions of epithelia cells
(1) protect, cover, and line other tissues
(2) filter biochemical substances
(3) absorb nutrients
(4) provide sensory input
(5) manufacture secretions
(6) manufacture excretions
(7) act as an interface layer that separates and defines the beginning and ending of different types of tissues.
What four attributes characterize epithelial tissue
- Epithelial cells are polar
- Epithelial cells have lateral surfaces that are connected to neighboring cells by junctional complexes.
- All epithelial cells lack blood vessels or capillaries.
- Although some epithelia lack nerves (for example, those in the stomach, intestines, and cervix), most epithelial cells are innervated and provide valuable sensory input.
Describe how epithelial cells are polar
They have a sense of direction relative to surrounding structures. Each epithelial cell has an apical surface and a basal surface, which are quite different from each other. The apical surface is the side of the cell that faces the lumen or body cavity, and the basal surface is the side of the cell that faces the underlying connective tissue.
Describe epithelial junctions
These junctions bring the cells into close apposition to one another, leaving little room for extracellular matrix. The matrix that surrounds epithelia therefore exists in very small quantities, if at all.
List 4 types of cellular junction
- Tight junction:
- Desmosome:
- Hemidesmosome:
- Gap junction:
Describe tight junction
Formed by the fusion of the outermost layers of the plasma membranes of adjoining cells. The matrix-filled space between cells is lost at the site of a tight junction. For centrally placed cells, the fusion occurs as a strip that wraps around the entire circumference of the cell In this way, an impenetrable barrier is formed that prevents the passage of substances from the luminal end to the basal end of the cell and vice versa.
Tight junctions are found in tissues in which there can be no leaks—for example, in the urinary bladder, where urine is held, or in the digestive tract, where tight junctions play a critical role in preventing the leakage of digestive enzymes into the bloodstream.
Desmones
A strong, welded plaque that connects the plasma membranes of adjacent cells. The bond is a mechanical coupling formed by filaments that interlock with one another like velcro. Intermediate filaments, may also extend from the desmosomic plaque into the cytoplasm of each cell like anchors. In this way, desmosomes form tough bonds between cells and therefore are found most commonly in tissues that undergo repeated episodes of tension and stretching, such as the skin, heart, and uterus.
Hemidesmosome:
junctions that look like half-desmosomes and link epithelial cells to the basement membrane.
Gap junction
Made of tubular channel proteins called connexons and extends from the cytoplasm of one cell to the cytoplasm of another. These transmembrane proteins allow the exchange and passage of ions and nutrients from one cell to another.
Gap junctions are most commonly found in intestinal epithelial cells, the heart, and smooth muscle tissue.
Not as important- The function of gap junctions in epithelial cells is not yet fully understood, but their ability to quickly transport electrical signals from one cell to another explains their presence in cardiac and smooth muscle cells, where they help coordinate contraction.
Explain how basement membrane acts as a partial barrier
It is a nonliving meshwork of fibers. Oxygen and nutrient molecules diffuse through the basement membrane from capillaries in the underlying connective tissue. Similarly, nutrient substances that are absorbed and waste that is excreted by the epithelium diffuse across the basement membrane into the blood supply of the connective tissue.
Role of cilia and microvilli in epithelial tissue
Microvilli increase the surface area of cells and allow more absorption and secretion. Ciliary movement occurs in coordinated “beats” that enable the efficient transport of material. In the trachea, cilia help propel mucus and debris up and away from the lungs toward the mouth. In the uterine tube, the beating motion of cilia encourages newly released ova into the oviduct, or infundibulum.
Where are cilia and microvilli found in epithelial cells
Microvilli are found on epithelial cells in the intestines and urinary tract. Cilia are found on the free surfaces of cells, usually in the respiratory and urogenital tracts.
Transitional epithelium is only found where
the urinary bladder
List the characteristics used to describe epithelial tissue
Number of layers and cell shape
What cells are generally rapidly dividing
epithelial
list the components of the neuron
Axon, dendrites and the perikaryon (body)
Epithelial cell shapes
Squamous
Cuboidal
Columnar
Epithelial cell layers
Simple - 1 layer
Pseudostratified 1 (modified simple, looks like more than 1)
Stratified - more than 1 layer
Transitional (more than one)
What are the two types of epithelial cells
sheets or glands
Describe the two poles of epithelial cells
Apical is towards the surface and Basal is towards the basement membrane
Basement Membrane
Foundation of epithelial cell
Nonliving network of fibers
-cements cells to underlying tissues
Helps prevent cells from being torn off
Parietal barrier to underlying tissue
Basal Lamina
Basement membrane
Surface specialization of epithelial tissue
Surface specialization varies depending on location and function
-Smooth
-Microvilli (Digestion system)
-Cilia
-Keratin
Simple Squamous Epithelium
Delicate and thin
Flat and smooth
Found lining surfaces involved in passage of gas or liquid
Extra- line capillaries, lungs, cheek cells
Simple cuboidal
Single layer of cube shaped cells
Nuclei aligned in single row
Found in area where secretion and absorption occur
Extra- think kidneys and urinary
Simple Columnar
Cells are elongated, closely packed together
(less common are simple ciliated columnar epithelia)
Nuclei aligned in a row at the base of cell
Some cells associated with absorption and secretion
includes goblet cells
Extra- digestive track,
Role of Goblet Cell
Makes secretions in simple columnar
Stratified Squamous Epithelium
Multilayered
Protect underlying tissues
Occurs in areas of body subject to mechanical stress
Outer layer continual being worn off
(replaces at equal rate from cells in deeper layers)
Skin, oral cavity, esophagus
Stratified Cuboidal
Generally occurs in two layers
Protects underlying tissues
Found primarily along large excretory ducts
- sweat glands, mammary glands and salivary glands
Stratified Columnar
Rare type of cell
Found respiratory, digestive and reproductive tracts
Pseudostratified Columnar
Layer is not truly stratified
- nuclei at varying levels
-not all cells reach luminal surface
- Every cell attaches to the basement membrane
Most are ciliated
Respiratory tract and portions of male reproductive tract.
Transitional Epithelium
Basal layer of cuboidal or columnar cells and a superficial layer of squamous cells
Leak proof membrane
Found in regions that need to expand and contract as part of their normal function
Ureters, urethra and urinary bladder
Glands
Cell or group of cells that manufacture and discharge a secretion
Glands are classified by
Presence or absence of ducts
Number of cells that compose them
shape of secreting ducts
Complexity of the grandular structore
Type of secretion
Manner in which secretion is stored
Endocrine Glands
Glands that do not have ducts or tubules and secretions are distributed through whole body
Produce and secrete hormones into bloodstream or lymphatic system
Part of the endocrine system
Exocrine Glands
Discharge secretions through ducts directly into local areas (except for goblet cell)
Unicellular or multicellular
Unicellular exocrine Gland
Goblet cell- composed of modified columnar epithelia. Secretes mucin
Multicellular Exocrine Gland
Composed of a secretory unit and a duct
Secretory unit -
usually surrounded by connective tissue rich in nerves and blood vessels
Rate of secretion- controlled by hormones and nervous influences
examples- sweat glands, salivary glands, sebaceous glands
Simple Ducts
An unbranched glandular duct
Compound ducts
A branched glandular duct
Alveolar
A rounded sac
Apocrine Glands
Store their secretions. Top part of cell is released into duct system
Holocrine
Glands store their secretions so that entire cell is destroyed in the act of releasing it’s product
Merocrine
Secretory glands that stay intact during the secretory process
serous fluid
Watery, high concentration of enzymes. A type of secretion.
Mucus
Thick, composed of glycoproteins
Connective tissues types
Loose
Adipose (fat)
Dense (ligaments and tendons)
Cartilage
Bone
Blood
Functions of connective tissue
Metabolic and structural connections between other tissues
protective sheath
Insulation
Reserve for energy
Framework
Medium for transporting substances throughout body
Role in the healing process and control of invading microorganisms
General characteristic of connective tissue
Most abundant by weight
Vascularized
3 distinct components - ground substances, extracellular fibers, cells
Ground substance of connective tissue
Medium through which cells exchange nutrients
Amorphous homogeneous materials
Envelopes and protects delicate cells
Obstacle for invading microorganisms
Collagenous fibers
connective tissue
Strong thick strands of protein collagen
Organized into bundles
Varying density and arrangement of fibers
(think tendons and ligaments
Reticular fibers
connective tissue
Thin, delicate, branched networks of collagen
Provide support for highly cellular organs (endocrine glands, lymph nodes, spleen, bone marrow, liver)
Also found around nerves, blood vessels, muscles fibers and capillaries
List the fibers of connective tissue
Collagenous fibers, reticular fibers, elastic fibers
Elastic fibers
Connective tissue
Composed of primarily protein elastin
Branched to form complex networks
Occur in tissues that stretch- vocal cords, lungs, skin, walls of blood vessels
Connective Tissue Major Cell Types
Fixed and transient
Fixed Cells
Remains in connective tissue
Involved in production and maintenance of matrix
list types of fixed cells
fibroblast (blood)
chondroblast (cartilage),
osteoblast (bone),
adipocyte (adipose/fat),
reticular cell - purpose not clear, immune?
Transient cells/Wandering cells
Passes in and out of connective tissue- diapedesis
Involved in repair and protection of tissue
Types- leukocyte, mast cell and macrophage
Loose connective tissue types
Areolar, adipose and reticular
Areolar Tissue
Most common type of connective tissue
Loose connective tissue
Tangle of random fibers and cells suspended in thick ground substance
Predominant cell is fibroblast
Functions to-
Surround and protect
Provide nutrients
( Is present in all mucus membranes)
Adipose tissue
Loose connective tissue
Highly vascular
Located throughout the body
Functions-
Energy storehouse
Thermal insulator
Mechanical shock absorber
Reticular Connective Tissue
Loose connective tissue
Thin, loosely arranged reticular fibers and fibroblasts suspended in ground surface.
Forms framework for organs (also called stroma)
Dense connective tissue types
Dense regular
Dense irregular
Elastic
Dense regular
Tightly packed parallel collagen fibers
- fibroblasts form rows
Relatively avascular
Found in- tendons, ligaments, sheets of fascia
Dense irregular
Thicker bundles of collagen than in dense regular
Fibers woven into single sheet
Locations – Dermis of skin, fibrous covering of organs, tough joint capsules
Elastic tissue
Composed primarily of elastic fibers
Parallel or interwoven pattern with fibroblasts and collagen
Found in- spaces between vertebrae, ligaments, walls of arteries, stomach, bronchi and heart
Specialized connective tissue types
Cartilage, bone, blood
Cartilage
Three types based on fiber in matrix -hyaline, elastic, fibrcartilage
More rigid than dense connective tissue and more flexible than bone
no nerve cells, avascular
Cells - chondrocytes in lacunae
Matrix- ground substance, tissue fluid, collagen & elastic fibers
Locations- joints, ears, nose, vocal cords, framework for bone formation
Bone
(Osseous connective tissue)
Hardest and most ridig connective tissue
Specialized matrix
- Collagen fibers (gives structure, is organic)
- Inorganic calcium salts
Well vascularized
- central Haversian canal
- canaliculi
Locations - skeletal frame
Blood
Matrix-
Ground substance - plasma
Fibrous component - protein
Cells-
Erythrocytes
Leukocytes
Thrombocytes - platelets
Hyaline
Smooth cartilage
most common
Most rigid cartilage - closely packed collagen fibers and enclosed within a perichondrium
locations - embryonic skeleton, tracheal rings, auricular cartilage, group plates of long bones, sternum-to-ribs connections
Elastic cartilage
Contains many elastic fibers in dense, branching bundles
Flexible
Locations- epiglottis and external ears
Firbocartilage
Usually found merged with hyaline cartilage in dense connective tissue
- Thick bundles of hyaline with no perichondrium
Designed to take compression
Locations- Between vertebrae of spine, between bones in pelvis and knee joint
perichondrium
Means surrounds cartilage
The perichondrium is a dense layer of fibrous connective tissue that covers cartilage in various parts of the body.
membranes.
Thin, protective layers of tissue linked together. The epithelial sheet bound to underlying connective tissue
Mucous, serous, cutaneous and synovial
Mucous membrane
Line organs with connections to outside environment (think tracts)
Composition
- Stratified squamous or simple columnar epithelia covering lamina propria
- submucosa connects mucosa to underlying layers
Generally produces large quantities of mucus
May contain goblet cells or multicellular glands
Some mucosae can also absorb (intestinal tract)
not as important- mucus is made of water, electrolytes and protein mucin
Serous Membrane
Cover the organs in the thoracic and abdominal cavities
Fold in on themselves and become pleura or peritoneum
- Visceral cover the organ
simple squamous epithelium
Produces thin, watery serosal fluid (transudate)
- Electrolytes but no mucus
- Creates moist and slippery surfaces
Cutaneous membrane
Organ is always exposed to outside environment therefor has keratinized stratified squamous epithelium
Epidermis (outer layer)
Attached to underlying layer-
Dense irregular connective tissue
Dermis
Nerve and blood supply
Synovial membrane
Line the cavities of the joints
- connective and adipose tissue covered by layer of collagen fibers and fibroblasts
- No epithelium
Manufactures synovial fluid
Effusion
Excessive fluid (serosal fluid)
Cutaneous membrane synonums
Integument, skin
Two types of cells that make up gut lining
Most are absorptive -simple columnar epithelial cells. (Apical surface has dense microvilli)
Also has goblet cells
