Tissue Types

Chapters 4.1-4.4

What is the primary definition of tissues in human anatomy?

Collections of specialized cells and cell products that perform a limited number of specific functions.

Approximately how many distinct cell types combine to form tissues in the human body?

There are approximately 200 distinct cell types in the human body.

What field of study is defined as the microscopic examination of tissues?

Histology is the study of tissues.

Which four basic tissue types form all the structures of the human body?

Epithelial tissue, connective tissue, muscle tissue, and neural tissue.

What five essential structural characteristics define epithelial tissue?

Closely bound cells, an exposed apical surface, basement membrane attachment, avascularity, and continuous regeneration.

How do avascular epithelial cells obtain necessary nutrients?

Diffusion across their attached basement membrane or exposed apical surface.

What are the four primary physiological functions of epithelial tissue?

Provide physical protection, control permeability, provide sensation, and produce specialized secretions.

How do exocrine secretions differ from endocrine secretions?

Exocrine secretions are discharged onto epithelial surfaces through ducts, whereas endocrine secretions are released directly into tissue fluid and blood as hormones.

What transmembrane proteins bind opposing cell membranes to each other and to extracellular materials?

Cell adhesion molecules (CAMs) interconnect large areas of opposing plasma membranes.

Which specific cell junction prevents the passage of water and solutes between adjacent epithelial cells (by sealing adjacent plasma membranes together w/ interlocking membrane proteins)?

Tight junctions

What continuous band deep to a tight junction ties an epithelial cell to the microfilaments of its cytoskeleton?

An adhesion belt

Which membrane proteins form the narrow channel within gap junctions?

Embedded membrane proteins called connexons

What structure locks opposing plasma membranes together using CAMs, proteoglycans, and a network of intermediate filaments linked to dense areas?

Desmosome

Which specialized cell attachment site anchors an epithelial cell to the noncellular basement membrane?

Hemidesmosomes

By approximately how much do microvilli increase the surface area of an epithelial plasma membrane?

20x

What is the primary function of cilia on ciliated epithelial surfaces?

Cilia beat in a coordinated fashion to move materials across the epithelial surface.

Where are unspecialized epithelial stem cells located within tissue?

Stem cells are located in the deepest layers of the epithelium near the basement membrane.

What two criteria form the basis for classifying epithelia?

Number of cell layers and the shape of the exposed surface cells.

Why are simple epithelia characteristic of regions where absorption or secretion occurs?

Their single cell layer is thin, which reduces the time required for materials to diffuse across the barrier.

What basic shape describes epithelial cells that appear thin, flat, and scale-like, with a central nucleus at the thickest portion?

Squamous epithelial cells

How do cuboidal epithelial cells appear in standard sectional view?

Square with neatly aligned nuclei near the center of each cell.

Where are columnar epithelial cell nuclei located relative to the cell's structure?

Crowded into a narrow band close to the basement membrane.

Which tissue type lines the exchange surfaces of the lungs (pulmonary alveoli) and the inner lining of blood vessels (cardiovascular interiors)?

Simple squamous epithelium

Where is simple cuboidal epithelium typically located in the human body?

Portions of kidney tubules and the ducts of digestive and endocrine glands.

Which epithelial lining covers the interior of the stomach and intestinal tract?

Simple columnar epithelium

Why is stratified squamous epithelium situated in regions such as the skin surface, oral cavity, and esophagus?

Its multiple cell layers protect underlying tissues against severe mechanical abrasion and chemical attack.

Where is stratified cuboidal epithelium located within the body?

Ducts of sweat glands and larger ducts of mammary glands.

Why is pseudostratified columnar epithelium not classified as a true stratified epithelium?

All cells in pseudostratified columnar epithelium remain in contact with the basement membrane.

Which tissue type lines the majority of the nasal cavity, trachea, and bronchi (primary respiratory airways)?

Pseudostratified ciliated columnar epithelium

What functional characteristic enables transitional epithelium to line the urinary bladder?

It can tolerate repeated cycles of stretching and recoiling without damage.

What is the specific name for unicellular exocrine glands?

Goblet/mucous cells

By what mechanism do merocrine exocrine glands release their secretions?

Exocytosis

How does apocrine secretion differ structurally from merocrine secretion?

Apocrine secretion involves the shedding of the apical portion of cytoplasm containing secretory vesicles, whereas merocrine leaves the cell completely intact.

What occurs to a glandular cell undergoing holocrine secretion?

The entire cell becomes packed with secretory products and then bursts apart, destroying the cell.

Which gland type produces an oily coating on hair follicles using holocrine secretion?

Sebaceous glands

What are the three main exocrine gland classifications based on the type of secretion produced?

Serous glands, mucous glands, or mixed glands.

What diagnostic procedure involves collecting and examining cells shed from epithelial surfaces?

Exfoliative cytology

What three basic components are shared by every type of connective tissue?

All connective tissues contain specialized cells, extracellular protein fibers, and ground substance.

What structures collectively constitute the extracellular matrix of connective tissue?

Extracellular protein fibers and fluid ground substance

What are the three major categories used to classify all connective tissues?

Connective tissue proper, fluid connective tissues, and supporting connective tissues.

Which permanent cell type in connective tissue proper produces extracellular (protein) fibers and ground substance?

Fibroblasts

What is the primary role of fibrocytes in connective tissue proper?

Maintain the extracellular protein fibers of connective tissue proper.

How do fixed macrophages differ functionally from free macrophages?

Fixed macrophages reside long-term in connective tissue for defense, whereas free macrophages migrate rapidly to active sites of injury or infection.

How does the internal anatomy of a typical adipocyte appear under microscopic examination?

A lipid droplet fills the cell interior, squeezing the nucleus and organelles against the outer margin.

What chemicals contained in mast cell vesicles trigger local defense responses following tissue injury?

Histamine and heparin

What are the three distinct types of protein fibers synthesized by fibroblasts in connective tissue proper?

Collagen fibers, elastic fibers, and reticular fibers.

What structural features distinguish collagen fibers from other connective tissue fibers?

Long, straight, unbranched, extremely strong, and flexible

What protein subunit endows elastic fibers with the ability to recoil after stretching?

Elastin

What structural pattern characterizes reticular fibers within organs?

Reticular fibers form a thin, branching, interwoven three-dimensional framework.

How does the syrupy consistency of connective tissue ground substance defend against infection?

Its dense consistency physically slows down the movement of pathogens through tissues.

Which three tissue types are classified as loose connective tissues?

Areolar tissue, adipose tissue, and reticular tissue.

Why does areolar tissue allow independent movement of the skin relative to deeper muscles?

Its open framework and elastic properties cushion underlying structures while absorbing movement forces.

What primary functions are served by adipose tissue?

Adipose tissue provides shock absorption, thermal insulation, structural padding, and energy storage.

Where is reticular connective tissue located in the human body?

Stroma of the liver, spleen, lymph nodes, and bone marrow

How are collagen fibers arranged in dense regular connective tissue?

Tightly packed in parallel alignment along lines of applied stress.

What functional connective structure connects skeletal muscles directly to bones?

Tendons

How do ligaments structurally differ from tendons?

Ligaments connect bone to bone and typically contain elastic fibers in addition to collagen.

Why does dense irregular connective tissue withstand forces applied from multiple directions?

Its collagen fibers form an interwoven meshwork running in varied directions.

What constitutes the liquid matrix of blood?

Plasma

Which formed element accounts for almost half the total volume of blood?

Red blood cells (erythrocytes) make up nearly half of blood volume.

How does lymph fluid originate within body tissues?

When interstitial fluid enters lymphatic vessels for filtration and recirculation.

What singular cell type resides within cartilage matrix?

Chondrocytes

What term describes the small matrix chambers occupied by chondrocytes and osteocytes?

Lacunae

Why does damaged cartilage demonstrate very limited self-repair capabilities?

Cartilage is completely avascular, so nutrients and repair materials must slowly diffuse through the matrix.

What fibrous and cellular layer surrounds and isolates cartilage structures from surrounding tissues?

Perichondrium

What are the three major histological types of cartilage?

Hyaline cartilage, elastic cartilage, and fibrocartilage.

Where is hyaline cartilage located in the adult human body?

Covers joint surfaces, connects ribs to the sternum, and supports respiratory passageways.

Which cartilage type forms the external flap of the ear (auricle) and the epiglottis?

Elastic cartilage

What structural feature makes fibrocartilage exceptionally resistant to compression shocks?

Dominated by densely interwoven collagen fibers with minimal ground substance.

Where is fibrocartilage found within the musculoskeletal system?

Between intervertebral discs, pubic pelvic bones, and within complex knee joints.

What chemical constituents dominate the matrix of bone tissue to provide rigid strength?

Insoluble calcium salt deposits organized around flexible collagen fibers.

How do osteocytes receive nutrients through the rigid calcified matrix of bone?

Osteocytes extend cytoplasmic processes through microscopic channels called canaliculi to reach blood vessels.

What covering sheath encloses outer bone surfaces outside of joint cavities?

The periosteum

What underlying genetic defect causes the clinical manifestations of Marfan syndrome?

The synthesis of an abnormally weak form of the carbohydrate-protein complex fibrillin.

Why is cardiovascular rupture the most severe threat in individuals with Marfan syndrome?

Weakened connective tissues in major arterial walls can burst under physiological pressure