Tissues

Question 1

What do tissues contribute to homeostasis?

Answer 1

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 …

Question 2

What are the 4 primary tissue types and their main function(s)?

Answer 2

1. Epithelial = covering
2. Connective = support
3. Muscle = movement
4. Nervous = communication

Question 3

Epithelial tissue = ?

Answer 3

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

Question 4

2 types of epithelial tissue = ?

Answer 4

1. Covering and lining epithelia - lining the trachea, boundary between air in the body lining the bronchi
2. Glandular epithelia - sweat glands

Question 5

List some functions of epithelial tissue

Answer 5

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

Question 6

5 structural characteristics of epithelial tissue ?

Answer 6

1. 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]
2. 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
3. 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
4. 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
5. 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

Question 7

What is a tight junction vs a desmosome

Answer 7

• 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

Question 8

What are the 2 classification criteria for epithelial tissue

Answer 8

1. Cell shape = squamous, cuboidal, columnar
2. Number of layers = simple (single), stratified (multiple)

Question 9

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?

Answer 9

1. Thin and permeable; filtration and diffusion (found in endothelium, kidney, lungs)
2. Thicker to be more functional; secretion and absorption (found in kidneys, tubules, small glands)
3. Taller with lots of microvilli to increase SA for transporters, lots of area for vesicles; secretion and absorption (GI tract)

Question 10

What is pseudostratified columnar epithelia?

Where can it be found?

Answer 10

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.

Question 11

What is stratified squamous ?

What is the most widespread example found in the body?

Answer 11

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

Question 12

What is transitional epithelia? Where can it be found?

Answer 12

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.

Question 13

Difference between endocrine and exocrine glands?

Answer 13

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

Question 14

What is a goblet cell?

Answer 14

Unicellular exocrine gland

Has no ducts

More apical areas accumulate a product forming a goblet shape due to swelling

Question 15

What are the 3 types of secretory methods? Give a brief description of each

Answer 15

1. 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
2. Holocrine = cell ruptures
   - Only oil producing sebaceous glands
   - cells ruptured are sacrificed
3. Apocrine = cell apex pinches off wih secretory product and repairs itself
   - Only apex of cell ruptures off releasing liquid rich products

Question 16

What kind of gland is the mammary gland classified as?

Answer 16

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

Question 17

What are the 5 main types of connective tissue ?

Answer 17

Mesenchyme (embryotic CT), CT proper, cartilage, bone and blood

Question 18

What are the main functions of CT?

Answer 18

Binding and supporting (CT proper/bone/cartilage)

Protecting (CT proper/ cartilage/ bone)

Insulating (adipose tissue)

Transporting (blood)

Question 19

What are the different structural elements of connective tissue ?

Answer 19

a) ground substance (matrix)
b) fibers (collagen/elastic/reticular)
c) cells (blasts/cytes)

Question 20

Briefly describe what ground substance is

Answer 20

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)

Question 21

What is a proteoglycan

Answer 21

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

Question 22

What are the 3 types of fibers within CT?

Answer 22

1. Collagen fibers - high tensile strength (sturdiness), they are the strongest and most abundant
2. Elastic fibers - elastin has coiled structure to allow stretch and recoil
3. Reticular fibers - thin collagen proteins; fine meshwork to support blood vessels, soft tissues, attachment sites for blood capillaries

Question 23

Difference between immature and mature cells in CT

Answer 23

Immature = “blast” forms
- actively dividing and synthesizing cells during growth and repair

Mature = “cyte” forms
- primarily provide level of maintenance

Question 24

List both the mature and immature cells for the following tissue types;
CT proper
Cartilage
Bone
Blood

Answer 24

Immature:
Fibroblasts; chondroblasts, osteoblasts, hemocytoblast

Mature:
Fibrocyte, chondrocyte, osteocyte, RBCs/WBCs/platelets

Question 25

What is mesenchyme?

Answer 25

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

Question 26

what are the 3 major tissue types for the 2 subclasses of CT proper; loose CT and dense CT

Answer 26

Loose CT = areolar, adipose, reticular Dense CT = dense regular, dense irregular, elastic

Question 27

Where can the different types of loose CT be found and what are their functions

Answer 27

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

Question 28

What are the different types of dense CT? where can they be found and what is their function?

Answer 28

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