Connective Tissue and Nutritional Science Quiz

Tissue Organization

• Tissues are groups of similar cells and extracellular material performing a common function. Examples include protection.
• Histology is the study of tissues
• Four main tissue types exist: epithelial, connective, muscle, and nervous. These tissues have varied structures and functions.

Epithelial Tissue Characteristics

• Covers body surfaces and lines body cavities.
• Forms the majority of glands.
• Composed of one or more layers of closely packed cells.
• Contains little to no extracellular matrix, and, importantly, no blood vessels.

Cellularity and Polarity

• Composed almost entirely of tightly packed cells.
• Has an apical surface exposed to either the external environment or internal body space. This surface may have microvilli or cilia.
• Has a lateral surface with intercellular junctions.
• Has a basal surface attached to connective tissue.

Attachment to Basement Membrane

• Complex structure produced by epithelium and connective tissue.
• Consists of three layers: lamina lucida, lamina densa, and reticular lamina.
• Contains collagen fibers and specific proteins and carbohydrates.
• Forms a selective barrier between epithelium and connective tissue.

Avascularity and Innervation

• Nutrients obtained across the apical or basal surface.
• Extensive innervation detects environmental changes in the region.
• Has a high regeneration capacity.
• Cells are frequently damaged or lost, but stem cells adjacent to the basement membrane frequently undergo mitosis.
• Replacement of lost cells is ongoing.

Epithelial Tissue Functions

• Physical Protection: Protects external and internal surfaces from dehydration, abrasion, and destruction
• Selective Permeability: Regulates the passage of molecules maintaining a barrier for certain substances.
• Secretion: Secretes specialized molecules by scattered cells or organized glands.
• Sensations: Contains nerve endings that gather info on touch, pressure, temperature, and pain (neuroepithelium).

Epithelial Tissue Classification

• Classification is denoted by a two-part name indicating the number of epithelial layers, and the shape of cells at the apical surface (the exposed end of the cell).

Simple Epithelium

• One cell layer thick.
• All cells in direct contact with basement membrane
• Found in areas with low stress levels.
• Functions primarily in filtration, absorption, or secretion.
• Examples: lining of air sacs of lungs, intestines, and blood vessels (endothelium).

Stratified Epithelium

• Two or more layers of epithelial cells.
• Only the basal layer is in direct contact with basement membrane.
• Found in areas subjected to mechanical stress.
• Better able to withstand wear and tear (e.g., skin).
• Cells continually regenerate at the basal layer as apical cells are lost.

Pseudostratified Epithelium

• Type of simple epithelium.
• All cells attached to the basement membrane.
• Appears layered due to cell nuclei distributed at various levels, with some cells not reaching the apical surface.
• Commonly ciliated (e.g., in respiratory system)

Epithelial Cell Shapes

• Squamous cells are flat, wide, and irregular, like floor tiles. Their nuclei are flattened.
• Cuboidal cells are approximately as tall as they are wide, and have spherical nuclei in the center of the cell.
• Columnar cells are slender and taller than wide, and have oval nuclei.
• Transitional cells change shape depending on whether the epithelium is stretched (e.g., in the bladder). They are polyhedral when relaxed and flattened when stretched.

Glands

• Glands are individual cells or multicellular organs composed predominantly of epithelial tissue.
• They secrete substances either for use elsewhere in the body or for elimination.

Endocrine Glands

• Lack ducts.
• Secrete hormones into interstitial fluid and then into the bloodstream.
• Act as chemical messengers affecting cell activity elsewhere.

Exocrine Glands

• Formed from invaginated epithelium in connective tissue.
• Connected with epithelial surfaces via a duct, lined with epithelium.
• Include: sweat glands, mammary glands, and salivary glands.

Unicellular Exocrine Glands

• Typically do not contain a duct.
• Locate close to their epithelial surface.
• A common example is the goblet cell.

Multicellular Exocrine Glands

• Contain numerous cells including acini (secretory portions)
• Contain ducts carrying secretions to epithelial surfaces
• Are surrounded by a fibrous capsule and partitioned into lobes.

Classification of Exocrine Glands

• Merocrine glands package and release secretions via exocytosis (e.g., salivary glands and some sweat glands).
• Apocrine glands release secretions by pinching off portions of the apical membrane, containing secretory product. (e.g., mammary glands).
• Holocrine glands accumulate a product in a cell followed by cell disintegration into a viscous mixture. (e.g., oil-producing glands of the skin).

Connective Tissue: Cells in a Support Matrix

• Most abundant tissue type.
• Supporting, protecting, binding organs, and tissues.
• Structure includes cells, protein fibers, and ground substance.
• Examples: tendons, ligaments, body fat, cartilage, bone, and blood.

Connective Tissue Cells: Resident Cells

• Include fibroblasts, adipocytes, mesenchymal cells, and fixed macrophages.
• Fibroblasts are the most abundant resident cells that secrete fibers and ground substance of the extracellular matrix.
• Adipocytes, also called fat cells, appear in clusters and when dominant, the tissue is termed adipose connective tissue.
• Mesenchymal cells are embryonic stem cells, which divide to replace damaged cells.
• Fixed macrophages are relatively large, irregular-shaped cells derived from monocytes that phagocytize (engulf) damaged cells and pathogens.

Connective Tissue Cells: Wandering Cells

• Continuously move through connective tissue, and are components of the immune system.
• May help repair damaged extracellular matrix.
• Examples: mast cells, plasma cells, free macrophages, and other leukocytes (white blood cells).

Connective Tissue Supporting Matrix: Protein Fibers

• Strengthen and support the tissue.
• Collagen fibers are strong, flexible, and resistant to stretching (numerous in tendons and ligaments).
• Reticular fibers are thinner than collagen and tough but flexible, abundant in stroma.
• Elastic fibers are branching wavy fibers stretching and recoiling easily found in skin, lungs, and arteries.

Connective Tissue Supporting Matrix: Ground Substance

• Nonliving material produced, mostly viscous (e.g., blood).
• Contains diverse large molecules and water.
• May be semisolid (e.g., cartilage) or solid (e.g., bone) to ensure solid support.
• Extracellular matrix is the ground substance and protein fibers combined.

Connective Tissue Functions

• Physical Protection: Protects delicate organs (e.g., skull and ribcage).
• Support and Structural Framework: Supports the body (e.g., bones).
• Binding of Structures: Binds structures together (e.g., ligaments).
• Storage: Stores energy (e.g., fat) and minerals (e.g., calcium and phosphorus).
• Transport: Transports substances (e.g., blood).
• Immune Protection: Protects against disease (e.g., leukocytes).

Clinical View: Scurvy

• Collagen is essential for supporting body tissues.
• Vitamin C is needed for healthy collagen fibers.
• Deficiency causes scurvy.
• Symptoms include weakness, sore gums, hemorrhages, abnormal bone growth.
• Treat with foods high in vitamin C or supplements.

Clinical View: Marfan Syndrome

• A genetic disorder of connective tissue.
• Involves skeletal, cardiovascular, and visual abnormalities (e.g. long limbs, fingers).
• Commonly causes dislocated joints, aortic weakness, abnormal heart valves, and a slipped lens.
• Often results in early death due to cardiovascular problems.

Integration of Tissues in Organs and Body Membranes

• Organs, composed of two or more tissue types, work together for specific complex functions.
• Examples of organs containing all four tissue types: the stomach and the heart.

Body Membranes

• Formed from epithelial tissue attached to underlying connective tissue.
• Line body cavities (e.g., lining of digestive system).
• Cover viscera (internal organs).
• Cover the body's external surface.
• Four main types: mucous, serous, cutaneous, and synovial.

Mucous Membrane

• Lines body compartments opening to the exterior.
• Includes digestive, respiratory, urinary, and reproductive pathways.
• Performs absorptive, protective, and secretory functions.
• Contains lamina propria (connective tissue) under the epithelium.
• Often lined with mucus.

Serous Membrane

• Lines body cavities that don't open to the exterior.
• Composed of simple squamous epithelium (mesothelium).
• secretes thin, watery serous fluid.
• Reduces friction between opposing surfaces or organs (e.g., lungs and their surrounding cavities).

Cutaneous Membrane

• Also known as skin
• Covers the body's external surface.
• Composed of keratinized stratified squamous epithelium, and underlying connective tissue.
• Protects internal organs and prevents water loss.

Synovial Membrane

• Lines joints.
• Composed of areolar connective Tissue, covered by a squamous epithelium lacking a basement membrane.
• Secretes synovial fluid that reduces friction among moving bone parts, and distributes nutrients to cartilage.

Tissue Development and Aging of Tissue

• Metaplasia is the change of mature epithelium to a different form (e.g., smokers experiencing metaplastic changes in trachea epithelium).
• Hypertrophy is an increase in size of existing cells in a tissue.
• Hyperplasia is an increase in number of cells in a tissue.
• Neoplasia is uncontrolled tissue growth.
• Atrophy is the shrinkage of tissue by decreasing cell numbers or size (e.g., disuse atrophy of muscles).

Tissue Necrosis

• Tissue death due to irreversible damage.
• Inflammatory response occurs in response to the damage.
• Examples include gangrene.

Aging of Tissues

• Support, maintenance, and replacement of cells/matrix less efficient after middle age.
• Structure and chemical composition of tissues become altered.
• Collagen declines.
• Tissues lose pliability/resilience.
• Repair is slower.
• Bones become more brittle and muscles/nervous tissues atrophy.
• Accelerated declines if poor diet or circulation.

Test your knowledge on connective tissues and the role of vitamins in health with this engaging quiz. Explore questions involving collagen synthesis, connective tissue functions, and the impact of vitamin deficiencies. Perfect for students of anatomy and nutrition!