Lecture 3 (ECM, Epithelial & Connective Tissues) Flashcards
What’s a tissue?
A group of similar cells and their intercellular structure joined together to perform a specific function.
How do you call the study of tissues?
Histology
How can you describe the Extracellular matrix (ECM)? What is it made of?
A complex mix of fluids and proteins that surround all tissues. Composed of nonliving intercellular material. Mainly made of water & dissolved ions, proteins & proteoglycans.
What are the four major types of tissues?
- Epithelial
- Connective
- Muscular
- Nervous
What are the main functions of the ECM?
- Helps bind tissues together structurally
- Allows local communication among ECM
What are the 5 functions of Epithelial tissue?
- Protection
- Sensory functions
- Secretion
- Absorption
- Excretion
Describe the protection function of the epithelial tissue.
The epithelium of our organs and our body surface, including the skin, provides basic protection from potentially harmful elements in our environment and from damage due to abrasion or other mechanical insult.
Describe the sensory functions of the epithelial tissue.
Modified epithelial structures allow the skin, nose, eyes and ears to sense and interpret the environment around us.
Describe the secretion function of the epithelial tissue.
Glandular epithelium is adapted for secretion of hormones, mucus, digestive juices, and sweat.
Describe the absorption function of the epithelial tissue.
The epithelial lining of the gut allows for the absorption of nutrients from the gut. The epithelial lining of the respiratory tract allows for the exchange of important gases between air in the lungs and the fluid of the blood.
Describe the excretion function of the epithelial tissue.
The unique epithelial lining of kidney tubules allows for the production and excretion of urine.
What are the characteristics of epithelial tissues that distinguish them from other types of tissues?
- Polarity
- Specialized contacts
- Supported by connective tissue
- Avascular but innervated
- Regeneration
On an image of an epithelial tissue, identify the apical, lateral and basal surface, as well as the basement membrane.
Describe the specialized contacts in the epithelial tissues.
At intervals between adjacent epithelial cells, the plasma membranes are modified to hold the cells together. Desmosomes and tight junctions.
What the difference between tight junctions and desmosomes?
Desmosomes: Anchoring junctions bind adjacent cells together like a molecular “Velcro” and help form an internal tension-reducing network of fibers. (skin)
Tight junctions: Impermeable junctions prevent molecules from passing through the intercellular space. (lining of intestines)
Describe the regeneration characteristic in epithelial tissues
Epithelium has a high regenerative capacity. New cells can replace old or damaged cells.
Describe the avascular but innervated characteristic in epithelial tissues
Epithelial tissues contain no blood vessels (avascular (no blood)), so O2 and nutrients must diffuse from capillaries in the underlying connective tissue through the permeable basement membrane.
Innervated means it is supplied by nerve fibers (has nerve connections)
Describe the characteristic in epithelial tissues
What’s a basement membrane and what does it do?
Basement membrane is extracellular material produced by the epithelium & underlying connective tissue)
The basement membrane reinforces the epithelial sheet, helping resist stretching and tearing forces, and defines the epithelial boundary.
Describe Simple Squamous Epithelium. What’s it function? Where can it be found?
- Flat
- Body’s most delicate type of epithelium
- Consists of only one layer of flat, scalelike cells, sparse cytoplasm
-Substance can easily diffuse or filter through this type of tissue - Absorption, diffusion, filtration
- Location: Air sacks of lungs, Lining of heart
Describe Simple Cuboidal Epithelium. What’s it function? Where can it be found?
- One layer of cuboidal cells resting upon a basement membrane (cubes)
- Cuboidal epithelial cells look like small bricks, which gives them strength and prevents them from being compressed.
- Functions: Absorption, secretion
- Location: Kidneys, ducts and tubules
Describe Simple Columnar Epithelium. What’s it function? Where can it be found?
- Location: Surface of the mucus membrane that lines the stomach, intestines, respiratory and reproductive tracts.
- Taller than they are wide, and the nuclei are located toward the bottom of each cell. (Many cells have modified structure)
- Function: Secretion of mucus, enzymes, absorption, moving of mucus.
Describe Pseudostratified Columnar Epithelium. What’s it function? Where can it be found?
- Single layer of tall cells that wedge together to appear as if there are 2 or more layers.
- Function: Secrete substances (mucus), propulsion of mucus through ciliary action.
- Location: Passageway of the upper respiratory system, segments of male reprod. system
Describe Stratified Squamous Columnar Epithelium. What’s it function? Where can it be found?
- Multiple layers of cells with typical scalelike squamous cells at the apical surface.
- Contains hard protein called keratin
- Location: Skin (epidermis), esophagus , vagina
- Function: Protection
Describe Stratified Cuboidal Epithelium. What’s it function? Where can it be found?
- Consists of 2 or more layers of cuboidal cells arranged over a basement membrane. Rare
- Function: Protection
- Location: Mammary glands, sweat glands, pharynx
Describe Stratified Transitional Epithelium. What’s it function? Where can it be found?
- Location: Organs and areas that require stretching. Lines in the urinary bladder and ureters.
- Function: Permits stretching
- These cells can flatten when tension forces the epithelium to expand.
What are the main functions of the connective tissue?
- Binds, supports and strengthens other tissues
- Protects and insulates internal organs
- Compartmentalizes structures such as skeletal muscle
- Major site of stored energy reserves (adipose fat)
- Main site of immune responses.
What are the general characteristics of connective tissue?
- Common origin: all connective tissues arise from the same embryonic tissue
- Degrees of vascularity: depends on the type of connective tissue
- Extracellular Matrix: mostly composed of ECM, cells are sparse
What are the structural elements of the connective tissue?
- ECM + cells
- ## ECM= ground substance (matrix) and fibers
Fibers in the ECM strengthen and support connective tissue. What are the three types of fibers found in the ECM?
- Collagen Fibers
- Reticular Fibers
- Elastic Fibers
The ground substance is the unstructured material that fills the space between the cells and contains the fibers. What is it composed of?
- Interstitial Fluid (IF)
- Cell adhesion proteins
- Proteoglycans
What are the characteristics of the collagen fibers?
- Strong and tough
- Most abundant
- Thick, wavy or straight, often forms bundles
- Resist stretching
- Made of collagen
What are the characteristics of the reticular fibers?
- Delicate
- Branch & support small structures such as capillaries & nerve fibers
- Made of special type of collagen
What are the characteristics of the elastic fibers?
- Stretchy (rubber bands)
- Slender, unbranching, very stretchy
- Recoil to original length after stretching
- Made of elastin
