Tissues Flashcards
What do tissues contribute to homeostasis?
Individual body cells are specialized for division of labour to maintain homeostasis
So that we can rely on specific tissues for their specific functions; nervous tissue specifically for communcation, muscle tissue specifically for movement …
What are the 4 primary tissue types and their main function(s)?
- Epithelial = covering
- Connective = support
- Muscle = movement
- Nervous = communication
Epithelial tissue = ?
Sheet of cells tha covers a body surface or lines a body cavity, often a single layer of cells
Creates boundaries between liquid, food and other substances enerting the body
2 types of epithelial tissue = ?
- Covering and lining epithelia - lining the trachea, boundary between air in the body lining the bronchi
- Glandular epithelia - sweat glands
List some functions of epithelial tissue
Protection; from outside and inside of the body, can be mechanical, chemical or infectious (against microorganisms) - skin
Absorbtion; break down products of digestion - GI tract
Filtration; filtering the waste from the blood - kidney
Excretion; moving of waste products to be discarded - kidney
Secretion; acid-secretion, secretion of digestive enzymes - glands/GI tract
Sensory reception - taste buds, olfactory membranes
5 structural characteristics of epithelial tissue ?
- Polarity - apical exposed to outside, basial to underlying tissue exhibits apical-basal polarity
- Apical surfaces often specialize having microvilli or cilia
- Because they are single layered, one surface faces up and the other down [facing the lumen into stomach/respiratory system = apical // sitting on supporting basal lamina facing out = basal] - Specialized contacts - tight junctions and desmosomes
- Because they need to be very strong so as to not let things like stomach acid leak
- Help epithelial cells to remain as a function layer lining the stomach as we digest food - Supported by connective tissue - basement membrane is composed of basal lamina (underlying supportive sheet of primarily glycoproteins) sitting on top of a reticular lamina (primarily collagen fibers)
- Important to provide attachment sites and physical support of epithelial cells to CT and for any necessary cell movement to retain a continuous structure as cells are being made - Innervated by avascular - will not come into contact with blood vessels therefore they rely on diffusion of oxygen and glucose that are within the underlying tissue
- Innervated = supplied by nerve fibers
- Avascular = contains no blood vessels - Regeneration - high regenerative capacity
- Can replace themselves during cell mitosis
- Because epithelial tissue ften creates boundaries where the body is vulnerable to lots of physical/chemical wear and tear they are easily destroyed
What is a tight junction vs a desmosome
- Tight junctions = important in preventing fluids from leaking
- Desmosomes = allow for plasma membranes of adjacent cells to firmly attach to each other with a slight space
What are the 2 classification criteria for epithelial tissue
- Cell shape = squamous, cuboidal, columnar
- Number of layers = simple (single), stratified (multiple)
Simple epithelia is used for absorption, secretion and filtration.
What are the characteristics and functions of;
1. Simple squamous?
2, Simple Cuboidal?
3. Simple Columnar?
- Thin and permeable; filtration and diffusion (found in endothelium, kidney, lungs)
- Thicker to be more functional; secretion and absorption (found in kidneys, tubules, small glands)
- Taller with lots of microvilli to increase SA for transporters, lots of area for vesicles; secretion and absorption (GI tract)
What is pseudostratified columnar epithelia?
Where can it be found?
Ciliated
Looks stratified but is not
Single layer - found in respiratory tract where cilia and mucus secretion are local specializations but have te appearance of stratified.
What is stratified squamous ?
What is the most widespread example found in the body?
Protective role; basal cells and most commonly cuboidal constantly undergo mitosis to keep regenerating below layers
Most widespread example is our skin
Apical layers are constantly sloshed off (replaced)
The furthest cells from the deepest layer contain less blood vessels - they provide physical protection but cells are essentially dead and no longer viable for mitosis
What is transitional epithelia? Where can it be found?
Stratified with mix of cuboidal and squamous
Found lining the bladder - an organ that has to fill (fills with urine and empties quite quickly , constantly changes in sectioned appearance based on filling level of urine)
Basal layers aer cuboidal and apical layers become increasingly flattened and squamous like.
Difference between endocrine and exocrine glands?
Exocrine = release of products through external secretion; mucuous, sweat, oil, salivary glands, liver, pancreas
Endocrine = release of products through internal secretion; ductless - products are hormones
Both can be unicellular or multicellular
What is a goblet cell?
Unicellular exocrine gland
Has no ducts
More apical areas accumulate a product forming a goblet shape due to swelling
What are the 3 types of secretory methods? Give a brief description of each
- Merocrine = exocytosis
- Most common type
- Constantly producing products and packing them in vesicles , vesicles are then released into lumen to move into duct towards target
- Ex. Pancrease, salivary glands, most sweat glands - Holocrine = cell ruptures
- Only oil producing sebaceous glands
- cells ruptured are sacrificed - Apocrine = cell apex pinches off wih secretory product and repairs itself
- Only apex of cell ruptures off releasing liquid rich products
What kind of gland is the mammary gland classified as?
Classified as merocrine
Mammals produce milk (containing glucose/proteins/ions) so for the most part is merocrine
Some lipids are produced by apocrine (oil producing)
Technically a mix of both merocrine and apocrine
What are the 5 main types of connective tissue ?
Mesenchyme (embryotic CT), CT proper, cartilage, bone and blood
What are the main functions of CT?
Binding and supporting (CT proper/bone/cartilage)
Protecting (CT proper/ cartilage/ bone)
Insulating (adipose tissue)
Transporting (blood)
What are the different structural elements of connective tissue ?
a) ground substance (matrix)
b) fibers (collagen/elastic/reticular)
c) cells (blasts/cytes)
Briefly describe what ground substance is
Interstitial fluid with cell adhesion proteins for attachment and detachments and proteoglycans
Acts as a molecule sieve (controls what gets through)
Is a material filling up spaces between cells
Fibronetcin and laminin are proteins that help cells attach to CT elements (fibers)
What is a proteoglycan
Bigger molecuels that contain a row of protein parts and sugar groups
They are able to bind to water molecules to help hold fluids and maintain hydration levels
What are the 3 types of fibers within CT?
- Collagen fibers - high tensile strength (sturdiness), they are the strongest and most abundant
- Elastic fibers - elastin has coiled structure to allow stretch and recoil
- Reticular fibers - thin collagen proteins; fine meshwork to support blood vessels, soft tissues, attachment sites for blood capillaries
Difference between immature and mature cells in CT
Immature = “blast” forms
- actively dividing and synthesizing cells during growth and repair
Mature = “cyte” forms
- primarily provide level of maintenance
List both the mature and immature cells for the following tissue types;
CT proper
Cartilage
Bone
Blood
Immature:
Fibroblasts; chondroblasts, osteoblasts, hemocytoblast
Mature:
Fibrocyte, chondrocyte, osteocyte, RBCs/WBCs/platelets
What is mesenchyme?
The first tissue formed from the mesoderm germ layer (embryonic tissue)
Mesenchymal cells, fluid ground substance and fine fibrils are the source of all other CTs
what are the 3 major tissue types for the 2 subclasses of CT proper; loose CT and dense CT
Loose CT = areolar, adipose, reticular
Dense CT = dense regular, dense irregular, elastic
Where can the different types of loose CT be found and what are their functions
Areolar - Gel like matrix with all 3 fiber types (most generic type), prime sit of edema during inflammatory reactions (swelling due to fluid)
- Found widely ditributed under epithelia of body (GI tract/respiratory system)
- Fnc. cushioning of organs, immunity and inflammation, fluid reservoir
Adipose - areolar CT modified to store nutrients in adipocytes ( fat- filled ), do NOT repreoduce
- Found under skin around kidneys and eyeballs, in bones and within abdomen, in breasts
- Fnc. fuel reservoir (fats), insulation, supports and protects organs from phys. trauma or heat loss, gives cushioning and stores fat
Retiucular - like areolar but only reticular fibers
- Found in lymphoid organs (lymph nodes, bone marrow, spleen), areas with WBCs where we need meshwork for attachment
- Fnc. supports free blood cells from formation of internal skeleton from fibers
What are the different types of dense CT? where can they be found and what is their function?
Dense regular - bundles of collagen fibers running parallel to direction of pull, white flexible tissue with great resistance to tension; organized in an orderly fashion
- Found in tendons, ligaments, aponeuroses (connecting structures to one another)
- Fnc. attachment with strength
Dense irregular - same as regular but collagen bundles are thicker and arranged irregularly (running in all directions gives more sturdiness)
- Found in dermis (protection against phys. trauma such as falling/pregnancy), submucosa of GI tract, fibrous capsules of organs and joints
- Fnc. Withstand tension exerted in many directions; strength
Elastic - like regular but very high content of elastic
- Found in some elastic ligaments
- Fnc. Where stretch tissue is needed
