Chapter 4: What Did You Learn?

Describe the basement membrane, its origins, and its functions

The basement membrane is a three layered, protein and carbohydrate structure secreted by the overlying epithelium and the underlying connective tissue. The basement membrane provides physical support for the epithelium, anchors the epithelium to the connective tissue, and acts as a barrier to regulate the movement of large molecules between the epithelium and the underlying connective tissue.

Distinguish between the parietal and visceral layers of the serious membrane.

The parietal layer of a serous membrane lines the body cavity, and the visceral layer covers organs.

What three categories are used to classify connective tissue types?

The three categories of connective tissue are connective tissue proper, supporting connective tissue, and fluid connective tissue.

Which intercellular junction ensures that epithelial cells act as "gatekeepers"?

The tight junction (zonula occludens) ensures that epithelial cells act as "gatekeepers."

Name the four types of body membranes

The types of body membranes include: (1) mucous membrane: lines body passageways. *digestive *respiratory *reproductive *urinary (2) serous membrane: *lines body cavities - the parietal layer and *covers organs - the visceral layer (3) cutaneous membrane: *the skin - both epidermis and dermis (4) synovial membrane: *lines some joints of the skeletal system

Describe the types of intercellular junctions between epithelial cells and where each is located

There are four types of intercellular junctions in the lateral surfaces of epithelial cell membranes. (1) tight junctions - encircle the cells near their apical surfaces and completely attach each cell to its neighbors. (2) adhering junctions - deep to the tight junctions and form a supporting and strengthening belt of protein fibers inserted into the plasma membrane. (3) desmosomes - a small region of protein fibers that hold cells together and provide resistance to mechanical stress at a single point. (4) gap junctions - provide a direct passageway through protein pores between cells for small molecules to communicate between neighboring cells.

Why is smooth muscle referred to as involuntary?

We do not have voluntary control over smooth muscle.

What are the three secretion methods of exocrine glands, and how does erach method mowrk?

(1) Merocrine secretion - occurs when small secretory vesicles move to the apical surface of the cell and release their contents by exocytosis. (2) Holocrine secretion - occurs when cells fill with an accumulated product and then the entire cell disintegrates releasing both product and cell fragments. (3) Apocrine secretion - occurs when the apical region of the cell 'pinches off' releasing some cellular fragments and product.

What are the similarities and differences between skeletal muscle, cardiac muscle and smooth muscle?

(1) Skeletal muscle tissue is composed of long, cylindrical thin muscle cells called muscle fibers, have more than one nucleus, are striated, attached to the skeleton, and are voluntary. (2) Cardiac muscle tissue is confined to the heart wall; its cells are often shorter than skeletal muscle cells, but they are striated like skeletal muscle cells; cardiac muscle cells usually are branched and they contain only one or two, centrally-located nuclei. Cardiac muscle cells are connected together by intercalated discs, which are strong gap junctions between the cells. (3) Smooth muscle tissue lacks the striations seen in the other two types of muscle tissue. It is involuntary and called visceral muscle because it is found in the walls of most viscera (organs), such as the stomach, urinary bladder, and blood vessels. Its contraction helps propel material.

List the epithelian type that is found (a) lining the lumen of the stoomach (b) lining the oral cavity (c) lining the urinary bladder (d) lining the tiny air sacs of the lungs

(a) simple columnar epithelium. (b) stratified squamous epithelium. (c) transitional epithelium. (d) simple squamous epithelium.

In what regions of the body would you expect to find hyakunbe cartilage, fibocartilage, and elastic cartilage, and why would thee supporting connective tissues be located in thee regions

*Hyaline cartilage is found in: - nose - trachea - larynx (voice box) - costal cartilage (the cartilage attached to the ribs) - articular ends of long bones - the fetal skeleton. *Hyaline cartilage functions primarily to support soft tissue: it also forms most of the fetal skeleton and in so doing it forms a model for future bone growth. Fibrocartilage is found: - in the intervertebral discs - the pubic symphysis - the menisci of the knee joint. *Fibrocartilage resists compression and is a good shock absorber. *Elastic cartilage is found: - within the epiglottis - and in the external earis *Elastic cartilage is extremely resilient and flexible.

Why is one epithelium referred to as "pseudostratified"?

A pseudostratified epithelium looks multilayered, or stratified, because the cells' nuclei are distributed at different levels between the apical and basal surfaces. However, although all of these epithelial cells are attached to the basement membrane, some of the cells do not reach its apical surface.

What characteristics are common to all connective tissues?

All connective tissue share a similar structural plan that includes: the presence of specific connective tissue cells that produce an extracellular matrix contain protein fibers to strengthen and support the connective tissue and an amorphous ground substance within which the cells and fibers reside.

What are some common characteristics of all types of epithelium?

All epithelia exhibit cellularity, polarity, attachment to underlying connective tissue, avascularity, innervation, and high regeneration capacity.

Why is epithelial cell regeneration important to the continues functioning of a holocrine gland?

Because each secretory cell is destroyed during holocrine secretion, the ruptured, dead cells are replaced by regeneration.

What two main characteristics are used to classify epithelial tissues?

Epithelial tissues are classified according to the number of cell layers and the shape of the cell at the apical surface.

Identify the three types of protein fibers in connective tissue proper.

Collagen fibers, elastic fibers, and reticular fibers make up connective tissue proper.

What type of intercellular junction provides resistance to mechanical stress at a single point?

Desmosomes provide resistance to mechanical stress at a single point.

What is the extracellular matrix? What are its main components?

Extracellular matrix is a nonliving material produced by and surrounding connective tissue cells. Protein fibers and ground substance are the components of the extracellular matrix.

What general name is applied to the supporting cells in nervous tissue?

Glial cells are the supporting cells in nervous tissue.

What are the main structural differences between dense regular and dense irregular connective tissue?

In dense regular connective tissue, collagen fibers are packed tightly, and aligned parallel to applied forces. In dense irregular connective tissue collagen fibers form a scattered meshwork array in which individual bundles of fibers extend in all directions.

What are Intercalated discs?

Intercalated discs are strong gap junctions between neighboring cardiac muscle cells. They permit the rapid transport of an electrical stimulus (nerve impulse) through many cardiac muscle cells at once, allowing the entire muscle wall to contract as a unit.

Compare loose connective tissue to dense connective tissue with respect to fiber density and distribution and amount of ground substance.

Loose connective tissue has a scattered distribution of fibers that are in relatively low concentration; it is primarily ground substance. Dense connective tissue has extensively distributed fibers, which are its primary component. Ground substance is sparse in dense connective tissue.

What is the function of mucus membranes?

Mucous membranes function in absorption, protection, and secretion.

What are the two basic parts of a multicellular exocrine gland?

Multicellular exocrine glands contain both a secretory portion and a conducting portion.

What type of muscle tissue has long, cylindrical, multinucleated cells with obvious striations?

Skeletal muscle tissue has long, cylindrical, multinucleated cells with obvious striations.