Unit 4: Tissues and Levels of Organization

what is a tissue

a group of cells working together to perform a specific function

what is Histology

the study of tissues

what are the two parts of the tissue

1. cells

2. Extracellular Matrix

where does ECM come from

it is secreted by the cells in the tissue

materials in the ECM

proteins, minerals, carbs, glycoproteins, water, and gases

what does the amount of ECM depend on

depends on the tissue type

definition of cell junction

where the membrane of adjacemcent cells meet

the three types of cell junctions

1. tight junction: impermeable junctions

2. desmosomes: anchoring junctions (holds things down)

3. Gap junctions: specialized cell junctions that create direct connections between the cytoplasm of adjacent cells, facilitating the exchange of ions, small molecules, and electrical signals

the structure of tight junctions

membranes of adjacent cells are fused together + the adhesion belt is located below the junction to rienforce the fusion

the function of tight junctions

prevents leakage of fluid between cells, this is important in hollow organs such as the bladder and stomach

examples of locations of tight junctions

lining of digestive organs

Desmosomes

anchoring junction

examples of specific locations of desmosomes

epidermis

structure of desmosomes

Contain adhesive material between cells. Is reinforced by the  cytoskeleton because also attaches to microfilaments or intermediate  filaments 

what is a hemidesmosome

half a desmosome + attatches epithelial cells to basement membrane

functiosn of desmosomes

a) Resistance to mechanical stress 

b) Prevents separation of cells 

Gap junctions

two cell membranes are connected by a protein channel

functions of gap junctions

1. allows ions to pass through

2. allows other communication chemicals to pass through

structure of gap junctions

adjacent cells link via protein channel

example of locations of gap junctions

a) Nerve cells 

b) Muscle cells 

major functions of epithelial tissues

1) Separates tissues/structures 

Forms boundaries 

2) Absorption & secretion 

3) Filtration

4) Protection 

5) Reduces friction 

locations of epithelium

1) External body covering (epidermis) 

2) Covering outside of organs (example: visceral peritoneum) 3) Lining the inside of hollow organs (example: the heart) 

4) Forms glands

characteristics of epithelium

1) Cells are tightly packed with little ECM 

2) Connective tissue (CT) is always located beneath to provide support,  nourishment & strength 

3) Polarity: superior & inferior regions of cells are different with respect to   structure & function 

what does apical mean

the top layer of epithelium + exposed to the outside world or the inside of hollow organs (may have cillia or microvilli to increase absorbtion

what is the basil region

the bottom layer of epithelium + is attatched by desmosomes to the basement membrane

function of basement membrane of epithelium

a) Anchors & supports 

b) Allows for exchange of materials between CT and  epithelial tissue; also can regulate the exchange

how do the epithelial tissues obtain nutrients since they are avascular

from the CT below them

does epithelium have a fast regeneration rate

yes

functions of simple epithelial tissues

1)  filtration

2) reduces friction

3) secretes serous fluid

where is the endothelium located

Inner lining of vessels & heart (function is to reduce friction).

where is the mesothelium

Lining of ventral body cavity (forms the serous membrane, both   the parietal and visceral layers).

the third nonspecific location of simple squamous tissue

 Lining the alveoli (air sacs) in the lungs (function is filtration)

can simple cuboidal cells have cilia or microvilli

yes

functions of simple cuboidal cells

1)  secretion

2) absorption

3)  moves substances (ciliated version)

location of simple cuboidal cells

lining of kidney tubules (secretion/absorption); lining the  oviducts (cilia sweeps the egg) 

what do goblet cells do

secrete mucus

functions of simple columnar cells

1) Secretion 

2) Absorption 

3) Moves substances (ciliated version) 

location of simple columnar cells

 lining of small and large intestine

Its there because of goblet cells. These cells make

functions of psuedostratified simple columnar

1) Secretion-the goblets cells secrete mucus

2) Moves substances (ciliated version) 

3) Small degree of protection from mechanical stress and invasion by pathogens 

location of psuedostratified

1. in general, pseudostratified is located in places where a small degree 

2. of protection from the external environment lining the nasal cavity, pharynx (throat) & trachea  all openings to the outside world. They need to be simple tissues so they don’t take up a lot of room

function of stratified epithelial

Protection from: 

a) Mechanical stress 

Because it's stratified, it gives protection, the cells at the top are squamous and flat and hard

b) Pathogen entry 

c) Liquid penetration  alcohol, that's how it burns, its growing through

location of stratified epithelial

1) Epidermis 

2) Oral cavity

3) Vagina 

Is the most widespread epithelial tissue 

two types of stratified squamous

1) Keratinized: contains keratin in apical layers. Keratin is a tough   protein and provides strength. Keratin also dehydrates the tissue   so the apical layers are dry. Upper layers contain dead cell. The   epidermis is one place it is located 

2) Non-keratinized: no keratin in apical layer. Apical layer is moist   & contains mostly living cells. The vagina is one place it is located 

stratified cuboidal functions

1)  secretion

2) is a rare tissue

locational of stratified cuboidal

In general, stratified cuboidal is located in places where  moderate amount of protection from the external environment is needed.  Is a very rare tissue.  

Specific locations: ducts lining the salivary glands (in the mouth) and  sweat glands (in the epidermis) 

functions of stratified columnar

1) Secretion 

2) Small degree of protection 

location of stratified columnar

 In general, stratified columnar is located in places where  moderate amount of protection from the external environment is needed.  Is an extremely rare tissue. Do not need to know specific body locations

structure of transitional epi

Structure: shape of apical cells vary

1. Squamous: when tissue stretched 

2. Cuboidal: when not stretched 

function of transitional epi

to allow stretching

location for transitional epi

1) Bladder 

2) Parts of urethra & ureter 

defintion of a gland

tructure that makes and/or secretes a product Can be made of 1 cell only or more than 1 cell 

exocrine gland def

secrete to the surface of epithelial tissue; have ducts;   are derived from epithelial tissue 

endocrine gland def

secrete to interstitial fluid; do not have ducts Secrete chemicals called hormones which eventually enter the   blood; most are not derived from epithelial tissue 

example of exocrine glands

a) Mucus, sweat, & oil glands (secrete to the external skin 

 surface) 

b) Liver & pancreas (secrete to the inside surface of a hollow  

 organ) 

c) Salivary glands (secrete to the inside surface of the mouth)  

functions of CT

1) “Connects” structures 

2) Support & protection 

4) Insulation 

5) Transport of substances in body 

6) Energy storage 

7) Immune system 

where is CT found

everywhere + the most abundant tissue type + amount of CT depends on the organ

what are CT derived from

all derived from same embryonic tissue called mesenchyme

are CT vascular

some are, some arent

what is more abundant in CT, cells or ECM

ECM + There is a lot of space between cells 

Amount of ECM varies between different CT 

ECM composition

is CT innervated

yes besides cartilage

what is CT regeneration dependant on

vascularity

ECM is made up of

1. ground substance

2. fibers

the three types of fibers in ECM

a) Collagen 

Structure: thick and strong 

Function: resists pressure and pulling forces

b) Elastic 

Structure: long and thin rubber band like

Function: allows for stretch and recoil

c) Reticular 

Structure: fine collagen fibers 

Functions: support (makes net shape)

the different types of ground substances

a) Fluid (as in blood) 

b) Gel-like (as in cartilage) 

c) Almost solid (as in bone)

what is ground substance made of

a) Fluid: allows nutrients to pass between blood supply &  

 cells 

b) Glycoproteins: glue like proteins; bind cells to ground  

 substance & fibers 

c) Large polymers: glycosaminoglycans (GAGs) 

Polysaccharides that attract water 

Functions : water balance & provide lubrication (

what are the different types of CT cells

1) “Blast” cells: produce the matrix and ground substance 

2) “Cyte” cells: maintain the matrix  

2) Immune system cells: 

a) Macrophages: engulf foreign cells & other material 

b) WBCs: start the immune response 

c) Plasma cells: secrete immune system proteins 

d) Mast cells: secrete histamine (to regulate blood flow) and   heparin (to inhibit blood clotting) 

3) Adipocytes: store energy 

types of connective tissue

a) Loose d) Cartilage 

b) Dense e) Bone 

c) Adipose f) Blood 

the two types of loose tissue

1. areolar-

   a) Cell types: has all cell types 

   b) Fibers: all 3 types

   c) is vascular and innervated

   d) Is the "Prototype" CT 

2. reticular

   a) Cell types: has all cell types 

   b) Fibers: all 3 types

   c) is vascular and innervated

   d) Is the "Prototype" CT 

where are reticular tissue found

1. lymph nodes

2. spleen

the three types of dense tissue

1. Dense regular

 2.dense irregular

3. Elastic connective Tissue

structure + function + location of dense regular tissue

Structure: 

a) Cell types:fibroblasts only

b) Fibers: collagen + tightly packed + arranged in parallel + regular arrangement 

c) Innervated & poorly vascular  

d) Most of ECM is collagen 

Functions: 

a) very strong: resists pulling forces coming from one direction

b) Attaches structures 

Locations:  

a) Forms ligaments (connect bones at joints) 

b) Forms tendons (connects muscles to bone or other   muscles) 

structure + function + location of dense irregular tissue

Structure: same as dense regular except: 

a)  collagen fibers thicker 

b)  fibers are irregularly arranged

Functions: 

a) very strong: resist pulling forces from all directions

b)  forms protective tissue sheets

Locations:  

a) Dermis  

b) Joint capsules 

c) Heart valves  

d) Covers muscles, bones, kidneys, & testes

structure + function + location of elastic tissue

Structure: both dense regular & dense irregular have an “elastic” version  of the tissue which has the same structure except the fibers are elastic (not  collagen) 

Functions: 

a) Very strong  

b) Allows for stretch & recoil 

Locations:  

a) Lungs  

b) Elastic arteries (near heart) 

structure + function + location of adipose tissue

Structure: 

a) Cell types: Adipocytes only

b) Fibers: not abundant

c) Cells are 90% of tissue 

d) Vascular & innervated 

Functions: 

a) adipocytes store fat (energy)

b) insulation

c) cushions and protects organs

Locations: 

a) Near areolar 

b) Subcutaneous layer 

c) Surrounds some organs (heart, eye, kidneys) 

chondroblasts

produce the tissue by secreting matrix &  

 reproducing to form new cells 

chondrocytes

mature cells 

Maintain healthy matrix 

Present after skeleton stops growing 

Definition of lacunae

hollow cavities in matrix where 

 clusters of chondrocytes are located 

the three types of cartilage

1) Hyaline cartilage: most abundant type 

Structure: 

a)  weakest type

b) fine collagen fibers- not visible

Functions: 

a) Firm but flexible support 

b) Absorbs shock 

Locations: 

(a) Tip of nose

 (b) Trachea 

(c) Costal cartilage 

(d) Forms   embryonic skeleton and 

(e) Epiphyseal plate 

2) Fibrocartilage: strongest type 

Structure: thick collagen fibers in rows 

• Rows alternate with rows of chondrocytes 

Functions: 

a) Strong & rigid support 

b) Resists heavy (crushing) pressure 

Locations: 

(a) Intervertebral discs 

(b) Pubic symphysis and 

(c) menisci-  (shock absorbing pads in joints)

3) Elastic cartilage 

Structure: abundant elastic fibers

Functions: 

a) Strong & elastic support 

b) Stretch & recoil 

Locations:

 (a) Outer ear and

 (b) Epiglottis 

the two cell types of bone tissue

a) Osteoblasts: produce the tissue by secreting matrix &   reproducing new cells 

b) Osteocytes: are located in lacunae 

Are mature cells that maintain the matrix 

the ground substance in bone tissue are described as

firm, rigid, & almost solid 

Caused by minerals such as calcium and phosphate 

which fibers are in bone tissue

mostly thick collagen but some elastic 

is bone tissue vascular and innervated

yes

the two types of bone

1) Spongy 

2) Compact 

the three types of mature blood cells

1) 3 types of mature cells: 

a) Erythrocytes (RBC) 

Function: Carry oxygen & CO2 (small amount) in 

 blood  

Most abundant cell in blood 

b) Leukocytes (WBC) 

Function: Immune system 

Very large cells 

Five different types

c) Platelets: are cell fragments 

Function: blood clotting 

Smallest & least abundant technically not a living cell

what is the ECM in blood tissues called

plasma

are there fibers in the ECM of bone tissue

no

functions of the matrix in bone tissue

1) Transport system 

Transports gases, nutrients, waste, & other chemicals 

2) Immune system 

3) Blood clotting 

functions of muscle tissues

1) Movement all three types of movement

2) Generates heat 

3) Maintains posture 

fibrous cells in muscle tissues are called

muscle fibers

are muscle tissues vascular

yes

do muscle tissue regenerate quickly

yes

three types of muscle tissues

1) Skeletal 

Locations: skeletal muscles (muscle that is attached to a bone)

 Function: whole body movement (voluntary movement) 

Characteristics 

a) Cells are multi-nucleate 

b) Cells arranged in parallel bundles 

c) Cells are striated (have alternating light & dark bands)

2) Cardiac 

Location: heart 

Function: pump blood (involuntary movement) 

Characteristics 

a) One nucleus per cell 

b) Cells are branched 

c) Cells are striated 

d) Intercalated discs: thick areas of cell membrane between adjacent cells

• Contain gap junctions

3) Smooth 

Location: walls of hollow organs 

Function: move material through the organ (involuntary movement) 

Characteristics: 

a) One nucleus per cells 

b) Fusiform cells 

c) Not striated 

nervous tissue location and function

IX. Nervous Tissue 

Located: nervous system (brain, spinal cord, & nerves) 

Functions: 

1) Detect stimuli 

2) Interpret stimuli 

3) Cause a response if necessary 

what are the most abundant type of cell

neurons

are nervous tissue vascular

yes

can neurons reproduce

no