A&P - Week 7

________ make up tissues

Cells

What is the study of tissues?

Histology

What are the 4 basic tissue types?

- Epithelial
- Connective
- Muscle
- Nervous

Why would tissues be stained under a microscope?
Example?

To enhance the contrast in microscope slides, or to show layers.
Example: White blood cells are often purple under the microscope, due to stains.

What is the epithelium?
Glandular epithelium?

It's a sheet of cells that covers body surfaces or cavities (ex. skin).
Glandular epithelium secretes substances (ex. salivary glands), and you're also able to sense through them.

Main roles of epithelial tissues?

Protection, absorption, filtration, excretion, secretion, sensory reception.

Why would somewhat insulative properties of the epithelium be important?

To prevent certain bodily materials to pass through into other organs.
Ex. the epithelium lines the GI tract to prevent consumed materials to pass through into other body systems, such as the lungs.

What does it mean that epithelial tissues have polarity?

They have a top (apical surface) and bottom (basal surface).

Apical surface

Exposed, upper side of the tissue

Basal surface

Lower, attached side of the tissue which faces inwards towards the body. It sits on the basal lamina.

Basal lamina

A non-cellular adhesive sheet that attaches the epithelial cells to the rest of the body.

How spaced out are epithelial cells?

Epithelial cells have little space between cells. They form tight junctions and desmosomes with neighbouring cells.

The epithelium is supported by the:

Basement membrane

What is the basement membrane of the epithelium composed of?

The basal lamina and the reticular lamina

Reticular lamina

A layer of extracellular material made of collagen fibres that is deep to the basal lamina

True or False:
Epithelial tissues are innervated.

True.
Epithelial tissues are supplied with nerve fibres.

True or false:
Epithelial tissues are vascular.

False.
Epithelial tissues are avascular (they have no blood vessels).

What is the regeneration capacity of epithelial tissues?
What does this mean?

High regeneration capacity.
This means that regeneration in order to repair damage (friction, hostile substances, etc.) is easy.

What is scarring a result of?

Damage to underlying connective tissue (not damage to the epithelium).

How many layers of cells are in a simple epithelium?

One layer

What are the main roles of the simple epithelium?

Absorption, secretion, and filtration

Where regions is the simple squamous epithelium located?

Regions where filtration or exchange of substances occurs.
Located in places where as little material as possible is needed, such as the lining of the lungs. It is delicate and easily damaged, but takes up little space.

What do simple cuboidal epithelium form?

The smallest ducts of glands or kidney tubules

Simple columnar epithelial line __________________.

The digestive tract.

Because simple columnar epithelium line the GI tract, the cells in the intestines can have ______________.

Microvilli

Stratified epithelia are made of ______ layers of cells.
What do these cells mainly do?

Many layers of cells.
These cells mostly provide protection

What is an important physical trait of stratified epithelia?
What does this mean in terms of substances?

Durability (protection).
This makes it hard for substances to pass through.

What does stratified squamous epithelium make up?

The external part of the skin, and it extends into every body opening

Where is stratified columnar epithelium found?

- The pharynx
- The male urethra
- Lining some glandular ducts

What is the transitional epithelium?
Where is it found?

It forms the lining of the urinary bladder and is specialized to allow cells to change shape and stretch.
Stretches when bladder is full, relaxes when bladder is empty.

Which layer of the transitional epithelium is more likely to be stretched?
What is another characteristic of this layer/surface?

The outermost (apical) surface.
This apical surface is also a water-tight barrier.

Endocrine glands.
Examples?

Ductless glands that secrete hormones by exocytosis (directly into the blood or lymph).
Secrete hormones which are chemical messengers that bind to specific receptors in target organs to generate some response.
Ex. Pituitary and pineal glands (brain), thyroid and parathyroid glands (near larynx), adrenal glands, pancreas, ovaries and testes.

Tissues that produce hormones are mainly:

Epithelial

Exocrine glands.
Examples?

Have ducts and secrete their products through an epithelial surface.
More numerous than endocrine glands.
Ex. Stomach acid, mucous, sweat, oil, salivary glands.

What are the most common unicellular glands?

Goblet cells

Where are goblet cells found?
What is their role?

In epithelial linings of intestinal and respiratory tracts.
They produce mucin.

What is mucin?

A sugar-protein that can dissolve in water to form mucus (a slimy protective and lubricating coating).

What do multicellular exocrine glands consist of?
What usually surrounds them?

A duct and a group of secretory cells.
They're usually surrounded by supportive connective tissue that supplies blood and nerve fibers to the gland.

How can multicellular exocrine glands be classified?

- By structure: Simple vs. compound, tubular vs. alveolar.
- By mode of secretion: Merocrine, holocrine, or apocrine.

Explain the ducts in simple glands

They have unbranched ducts

Explain the ducts in tubular glands

Secretory cells form long ducts that can be straight or coiled.

Explain the ducts in alveolar/acinar glands

Secretory cells form pockets/sacs.

How can you distinguish between simple tubular and simple alveolar ducts?

Simple tubular: More tube-like.
Simple alveolar: More pocket-like.

Compound gland

The duct branches to more than one group of secretory cells.
Tubuloalveolar glands have both tubular ducts and alveolar pockets/sacs.

How do merocrine (eccrine) glands secrete products?
How quickly are they secreted?
Examples?

By exocytosis.
They're secreted as they're produced.
Ex. Sweat, saliva, pancreatic juices.

How do holocrine glands release their contents?
Examples?

They accumulate products within the cell, and then rupture.
Ex. Sebaceous oil glands under the skin.

How do apocrine glands release their secretions?
Examples?

By budding off a portion of the cytoplasm.
Ex. Lactating mammary glands (modified sweat glands).

______________ is the most abundant and widely distributed of the primary tissues

Connective tissue

What are the major functions of connective tissue?

- Binding
- Support
- Protecting
- Insulating
- Storing reserve fuel
- Transporting substances (blood)

What are the 4 main classes of connective tissue?

- Connective tissue proper
- Cartilage
- Bone
- Blood

All connective tissues arise from:

An embryonic tissue called mesenchyme

Most connective tissue is highly vascularized, but __________ and ______________ are not.
Why is this?

Tendons and cartilage (and ligaments).
This is because they're too densely built and there is no space for blood vessels.

Connective tissue is composed mainly of:

Nonliving extracellular matrix that separates the cells of the tissue.

What is the extracellular matrix?

A protein-sugar mesh. This matrix supports cells so that they can bear weight and withstand tension.

The type of connection in a specific area is determined by:
Ex. Bones being hard is due to minerals - they wouldn't get their density if they were merely cells. What are minerals in this example?

The extracellular matrix.
In the example, the minerals in bones are the ground substance.

All connective tissues have 3 main elements:

- Ground substance
- Cells
- Fibres (protein)

What makes up the extracellular matrix?

Ground substances and fibres

What is the name for immature cells?
What is their role?

"Blast cells".
These cells actively secrete ground substances and extracellular fibres.

Where are the following cells found:
- Fibroblasts
- Chondroblasts
- Osteoblasts
What can their names tell us about them?

- Fibroblasts: Connective tissue proper
- Chondroblasts: Cartilage
- Osteoblasts: Bone
The suffix "blast" tells us that they're immature cells.

What is the name for mature cells?
What is their role?

"Cyte cells".
These cells are less active and help maintain the health of the matrix.

What can the following cells tell us about their life stages and roles:
- Osteoblasts
- Osteocytes

- Osteoblasts: Immature. Active builders.
- Osteocytes: Mature. "Maintenance".

What do fat cells store?

Nutrients

What is the role of white blood cells?
What are some names of common white blood cells?

Respond to tissue injury.
Neutrophils, eosinophils, lymphocytes (including plasma cells).

What is the role of mast cells?

They initiate a local inflammatory response against foreign microorganisms they detect.

Where are white blood cells frequently found?

They can go (pretty much) anywhere, and they often patrol connective tissues near the skin since this is where many pathogens enter.

What are macrophages?

Phagocytic white blood cells that "eat" dead cells and microorganisms as part of their function in the immune system.
"Destruction cells".

- What is ground substance?
- What does it consist of?
- What determines its consistency?

- An unstructured gel-like (depending on extracellular material - could be mineral deposits ex. bone) material that fills the space between the cells.
- Consists of interstitial fluid, glue-like adhesion proteins, proteoglycans (sugar proteins), and protein fibres.
- Water is trapped in varying amounts, affecting the viscosity of the ground substance.

What is the main role of fibres in connective tissues?

To provide support

Characteristics of collagen fibres

Very strong and provide high tensile strength to the connective tissue.
Durable, but little to no stretch (ex. scars).

What do elastic fibres contain? What does this mean for the fibre?

They contain elastin.
This allows these fibres to be stretched and recoiled.

What are reticular fibres?

Fine, collagenous (but not the same as collagen) fibres that form branching networks where connective tissue contacts other types of tissues.
"Open mesh" - almost like a net, which increases surface area.

Purpose of areolar connective tissue?

Serves to:
- Support and bind body parts
- Contain body fluids
- Defend against infection
- Store nutrients

Areolar connective tissue is the universal __________________ between other tissues.

Packing material

Characteristics of adipose (fat) tissue

Richly vascularized tissue that functions in nutrient storage, protection, and insulation.

Adipose tissue:
Brown fat vs. White fat

Brown fat: Uses lipids to produce heat (uses calories. Lots in babies).
White fat: Stores calories. Lots in older people.

What does reticular connective tissue form?
What does this support?

Forms the internal mesh-like stroma.
This stroma supports the lymph nodes, the spleen, and bone marrow.

What does dense regular connective tissue contain?
What does this tissue make up?

Contains closely packed bundles of collagen fibres running in the same direction.
Makes up tendons and ligaments (attaching muscle & bone as well as bone & bone).

Is adipose tissue vascular or avascular?

Vascular

Is dense regular connective tissue vascular or avascular?

Avascular

Is dense irregular connective tissue vascular or avascular?

Vascular

What is a characteristic of reticular connective tissue (in terms of swelling)?

It has the capacity of swelling if the organ is "activated". This swelling is mostly fluid, and the tissue is able to grow without damage (ex. lymph nodes).

- What does dense irregular connective tissue contain?
- How is this arranged?
- Where is this tissue found?

- Thick bundles of collagen fibres.
- These fibres are arranged in an irregular fashion (running in more than 1 direction, as opposed to dense regular connective tissue).
- This tissue is found in the dermis.

Why benefit is there when a tissue (collagen fibres) are running in more than 1 direction? (Ex. dense irregular connective tissue).

This tissue is more damage resistant as opposed to collagen fibres which run in 1 direction (ex. dense regular connective tissue).

What is the main characteristic of elastic connective tissue?

Its stretchiness compared to dense regular connective tissue.

True or False:
Elastic connective tissue is found in almost every human body part.

False.
This type of tissue is only found in select locations.

Is cartilage vascular or avascular?

Avascular

What does cartilage grow from?

Chondrocytes

Is cartilage innervated?

No (lacks nerve fibres)

Chondrocytes are found in cavities called ___________, which are essentially empty spots.

Lacunae

How does cartilage receive nutrients?

From the membrane surrounding it (the perichondrium). This is because it's avascular.

What are the 3 types of cartilage?

- Hyaline cartilage
- Elastic cartilage
- Fibrocartilage

- Hyaline cartilage.
- What are its traits?
- What is included/where is it found?

- The most abundant skeletal cartilage.
- Provides firm support with some pliability.
- Includes the articular, costal, respiratory, and nasal cartilages, the tips of long bones and cartilage of the ribs.

Elastic cartilage.
Located where?

More flexible than hyaline.
Located in places where strength and exceptional stretch are needed, such as the external ear and the epiglottis of the larynx.

Where is fibrocartilage located?

In places that must withstand lots of pressure or stretch, such as the cartilages of the knee and the intervertebral discs.
This is almost like bone (due to its density).

What are the 2 ways that cartilage grows?

- Appositional growth: Cartilage gets bigger from the perichondrium. A new matrix is laid down on the surface of the cartilage (grows from the outside).
- Interstitial growth: Occurs when the cartilage matrix expands from the middle due to division of lacunae-bound chondrocytes and secretion of matrix within the matrix (cartilage is inflated from inside-out).

When does calcification of cartilage occur?

During normal bone growth in youth as well as during old age.

True or False:
Hardened cartilage is the same as bone.

False.

What does osseous tissue mean?

Bone

Traits of osseous tissue

An exceptional ability to support and protect body structures (due to its hardness, determined by additional collagen fibres ad calcium salts found in the extracellular matrix).

True or False:
Blood is classified as a connective tissue.
Why is this?

True.
It develops from mesenchyme and consists of blood cells and plasma protein fibres surrounded by blood plasma.
The fibres are soluble proteins that precipitate during blood clotting.