Tissue Organization​ I

Week 4-5

Name the 4 types of tissues

1. Epithelial

2. Connective

3. Muscle

4. Nervous

What is a tissue?

Groups of similar cells that perform a common function​

What are the 6 characteristics of Epithelial Tissue?

1. Cellularity

2. Polarity

3. Attachment to a Basement Membrane

4. Avascular

5. Extensive Innervation

6. High Regeneration Capacity

What does it mean for Epithelial Tissue to have Cellularity?

It’s composed of tightly packed cells ​

What does it mean for Epithelial Tissue to have Polarity?

It has an apical and basal surface

What is a Apical Surface? Basal Surface?

Apical Surface → exposed to ​external environment or internal body space​

Basal Surface → fixed or deep attachment site​

What is the Basement Membrane?

Layers that act like “glue” that attach to underlying connective tissue​

What is the Basement Membrane attached to?

Basal Surface

Avascular

Lack of blood vessels

Extensive Innervation​

Supplied by many nerves to detect stimuli ​

What function or ability of Epithelial Tissue shows high regeneration capacity?

Frequent cell division​

Why is high regeneration capacity important for Epithelial Tissue?

Allows for continuous repair and replacing of cells lost to daily wear, tear, and environmental damage

What are the 4 functions of Epithelial Tissue?

1. Physical Protection

2. Selective Permeability

3. Secretions

4. Sensations

Why is it important for Epithelial Tissue to provide physical protection?

Prevents it’s internal and external surfaces from dehydration, abrasion, and destruction​

What do epithelial cells form?

Glands

How is Epithelial Tissue classified?

1. Number of Cell Layers

2. Cell Shape

What are the 3 categories of numbered cell layers when classifying Epithelial Tissue?

1. Simple

2. Stratified

3. Pseudostratified

Simple Epithelium

One cell layer → all cells in direct contact with basement membrane​

Provide an overview of Simple Epithelium (what, environment, function)

• One cell layer, all cells in direct contact with basement membrane​

• Found in areas where stress is minimal​

• Filtration, absorption, or secretion​

Stratified Epithelium

Multiple cell layers​

Provide an overview of Stratified Epithelium (what, function)

• Multiple cell layers​

• More structural support and protection​

• Basal cells regenerate continuously​

Pseudostratified Epithelium​

One cell layer (Simple Epithelium)

• Appears stratified because nuclei are at different levels​

• All attached to base, but not all reach surface​

What are the 4 categories of cell shape (at apical surface when classifying Epithelial Tissue?

1. Squamous

2. Cuboidal

3. Columnar

4. Transitional

Squamous (Cell Shape)

• Flat, wide, irregular shape​

• “Floor tiles,” flattened nucleus​

Cuboidal (Cell Shape)

• As tall as they are wide, ​

• Cubes with rounded edges, spherical nucleus​

Columnar (Cell Shape)

• Slender and taller than they are wide​

• Oval nucleus​

Transitional (Cell Shape)

• Change shape when stretched​

What makes the Transitional cell shape in Epithelial Tissue special?

Only urinary system ​

Simple Squamous Epithelium​

• Delicate​

• Thinnest possible barrier ​

Which type of Epithelial Tissue provides the thinnest barrier? Why?

Simple Squamous Epithelium​

• Allows movement of molecules and ions across layer​

Simple Cuboidal Epithelium​

• Absorption and Secretion

  • forms secretory tissue of most glands and ducts​

• Usually arranged in circles (glands and tubes)​

Simple Columnar Epithelium​

• Absorption and secretion​

• 2 Types:

  • Nonciliated

  • Ciliated

Nonciliated Simple Columnar Epithelium

• Contains microvilli​

• May contain goblet cells​

• Secrete mucus​

Ciliated Simple Columnar Epithelium

• Cilia that project from surfaces of cell​

• Mucus covers the apical surface and is moved along by cilia​

  • Goblet cells​

Pseudostratified Columnar Epithelium​

• Protection

• 2 Types:

  • Ciliated

  • Nonciliated ​

Ciliated vs. Nonciliated Pseudostratified Columnar Epithelium​

1. Ciliated ​

• Cilia on apical surface

• Goblet cells

​

2. Nonciliated

• Lacks cilia and goblet cells​

• Rare, lining of male urethra​

Stratified Squamous Epithelium​

• Protection from abrasion​

• Adapted to protect from friction​

• Stem cells continuously divide​

• Two Types:

  • Keratinized

  • Nonkeratinized​

Keratinized Stratified Squamous Epithelium​ (what and where)

• Superficial layer composed of cells that are dead

  • Lack nuclei and organelles​

• Epidermis of skin​

Keratin

Tough, protective protein that strengthens the tissue

Nonkeratinized Stratified Squamous Epithelium​ (what and where)

• Lack keratin and remain alive at apical layer

  • All layers have nuclei​

• Kept moist at apical layer with secretions of saliva or mucus​

• Oral cavity, throat, esophagus, vagina, anus​

Stratified Cuboidal Epithelium​

• Protection and secretion​

• Forms walls of exocrine ducts in glands​

Stratified Columnar Epithelium​

• Only apical layer is columnar​

• Protects and secretes​

• Goblet cells​

What type of Epithelium tissue is rare?

Stratified Columnar Epithelium​

Transitional Epithelium​

• Limited to urinary tract​

• Bladder, ureters, urethra​

• Accommodates urine volume changes in bladder​

  • Changes appearance depending on if it is in relaxed or stretched state​

What are the 2 states of Transitional Epithelium​?

• Relaxed state (collapsed) → when bladder is empty

  • Rounded apical cells​

  
  

• Stretched state (distended) → when bladder is full

  • Flattened apical cells​

Gland

Secrete substances either for use elsewhere in the body or for elimination from the body​

What are glands composed of?

Epithelial Tissue

What are the 2 types of glands? What do they do

Endocrine and Exocrine

Endocrine Gland

• No ducts​

• Secrete hormones to enter into blood for transport

Exocrine Gland

• Secretions exit body or organ​

• Maintain connection with epithelial surface through a duct

• 2 Types:

  • Unicellular

  • Multicellular​

Multicellular vs. Unicellular Exocrine Gland

Multicellular → uses ducts​

• Ex. Secrete mucus, sweat, oil, and milk

​

Unicellular → ​no duct​, located close to surface​

• Ex. Goblet cells​

What are the 2 components of a Multicellular​ Exocrine Gland?

Acinus → produce secretion

​

Duct → tube to transport secretion to epithelial surface​

What qualities of Connective Tissue makes it different from other tissue types?

Most diverse, abundant, and widely distributed of the four tissue types​

What are the 3 functions of Connective Tissue?

1. Support

2. Protect

3. Bind

What are the 3 traits of all Connective Tissue?

1. Derived from mesenchyme ​

2. Vascular​

3. Range of regenerative capacity ​

What are the differences in regenerative capacity ​between bone and cartilage?

Bone → highly regenerative

Cartilage → not regenerative​

What are the 3 components of Connective Tissue structure?

1. Cells​

2. Protein fibers​

3. Ground substance​

Protein Fibers and Ground Substance makes up what structure in Connective Tissue?

Extracellular Matrix

What are the 2 types of cells in Connective Tissue?

-Blast and -Cyte Cells

-Blast Cells (Connective Tissue)

Immature cells that actively build and secrete extracellular matrix

-Cyte Cells (Connective Tissue)

Mature cells that maintain extracellular matrix

What are the 3 types of Protein Fibers in Connective Tissue?

1. Collagen Fibers

2. Reticular Fibers ​

3. Elastic Fibers​

Collagen Fibers​ (what and where)

Strong, flexible, and resistant to stretch

• Tendons and Ligaments​

Reticular Fibers (what and where)

Forms a branching, interwoven framework (tough but flexible)​

• Structural support in organs​

Elastic Fibers​

Stretch and recoil easily (elastin)​

• Abundant in skin, blood vessels, lungs (stretch)​

Ground Substance​

• Substance material produces by CT cells ​

• Protein fibers and cells reside here​

What individual component takes up the majority of space in Connective Tissue?

Ground Substance

What are the 3 traits/types Ground Substance can have?

• Viscous (blood)

• Semisolid (cartilage)

• Solid (bone)​