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Questions and Answers
What is the primary function of epithelial tissue?
Which type of gland releases hormones directly into the bloodstream?
Which type of secretion involves the shedding of the cytoplasm?
Which type of epithelial tissue is described as having layers of cells covering surfaces?
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What type of locomotion do multicellular exocrine glands typically have?
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What type of secretion is released by merocrine glands?
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Which of the following is an example of a unicellular gland?
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What characterizes the intercellular connections in epithelial tissue?
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What happens to the epidermis as a person ages?
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Which type of sweat gland produces a sticky secretion primarily found in certain body areas?
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Which pigment provides some protection against UV radiation?
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What is a common characteristic of eccrine sweat glands?
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How does blood flow and oxygenation affect skin color?
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Which vitamin production declines with aging?
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What is the primary role of insensible perspiration?
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What happens to the number of myoepithelial cells surrounding apocrine sweat glands as a person ages?
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Which type of cellular junction allows for rapid communication and passage of small molecules?
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What is the primary purpose of tight junctions in epithelial cells?
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Which type of junction is primarily responsible for connecting cells to the basement membrane?
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Which process is initiated following tissue injury and involves the destruction of damaged tissue?
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What occurs when necrotic tissues and cellular debris accumulate in a wound?
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Which tissues are noted to regenerate poorly after injury?
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What are some factors contributing to loss of skin turgor?
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What can perfectly describe the effect of aging on the skin according to the content?
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What is the main function of sensible perspiration?
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What is the primary function of compact bone compared to spongy bone?
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What is the function of the periosteum?
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Which hormone decreases blood calcium levels?
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What is the role of osteoblasts in bone health?
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What happens to bone mass during inactivity?
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Which structure is responsible for nutrient exchange in bone?
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What is the primary role of endosteum in bone?
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What features differentiate red bone marrow from yellow bone marrow?
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Which type of ossification is involved in forming flat bones of the skull?
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What hormone is produced by the C-cells in the thyroid gland to decrease calcium levels in the blood?
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Which joint classification is characterized as immovable?
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What type of synovial joint allows for movement in three planes?
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Which ligaments or structures help stabilize synovial joints?
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Which of the following is NOT a type of synarthrotic joint?
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Which of the following describes a movements pattern of two planes?
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What is the primary function of tendons around a joint?
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What is a bursa?
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Study Notes
Epithelial Tissue
- Epithelial tissue covers exposed surfaces, lines internal passageways, and forms glands
- Epithelia are layers of cells covering surfaces, while glands are structures that produce fluid secretions
- There are two types of epithelial tissue: covering and lining epithelia, and glandular epithelia
Types of Epithelia
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Cuboidal Epithelia
- Simple Cuboidal Epithelia: Involved in secretion and absorption, found in glands and kidney tubules
- Stratified Cuboidal Epithelia: Relatively rare, found in ducts of sweat glands and mammary glands
Glandular Epithelia
- Glands are collections of epithelial cells that produce secretions
- Endocrine glands: release hormones that enter the bloodstream, have no ducts (example: thyroid gland)
- Exocrine glands: produce exocrine secretions that are discharged onto epithelial surfaces through ducts (example: sweat glands)
Gland Structure
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Unicellular Glands: Single-celled glands
- Goblet cells: unicellular exocrine glands found in the epithelia of intestines; secrete mucin, which mixes with water to form mucus
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Multicellular Glands: Classified by structure and type of secretion
- Examples: sweat glands, oil glands, salivary glands
- Simple Glands: Have a single continuous duct
- Compound Glands: Have branched ducts
- Tubular Glands: Have tubular secretory units with straight or coiled tubes
Types of Secretion
- Merocrine secretion: Released by secretory vesicles through exocytosis (example: merocrine sweat glands)
- Apocrine secretion: Released by shedding cytoplasm (example: mammary glands)
- Holocrine secretion: Released by cells bursting, killing gland cells. Gland cells are replaced by stem cells (example: sebaceous glands)
- Serous glands: Secrete watery secretions
- Mucous glands: Secrete mucins
- Mixed exocrine glands: Secrete both serous and mucous secretions
Cell Junctions
- Cell junctions form bonds with other cells or extracellular material
- Gap junctions: Rapid communication, allow small molecules and ions to pass, coordinate contractions in heart muscle (example: heart muscle cells)
- Tight junctions: Prevent passage of water and solutes, keep enzymes, wastes and acids in the lumen of the digestive tract (example: lining of digestive tract)
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Desmosomes: Attach cells together, allow bending and twisting.
- Spot desmosomes tie cells together
- Hemidesmosomes attach cells to the basement membrane
Inflammation
- Inflammation is the body's response to injury, triggered by trauma or infection
- Damaged cells release prostaglandins, proteins, and potassium ions
- Damaged connective tissue activates mast cells
- Lysosomes release enzymes that destroy injured cells and attack surrounding tissues; this process is called necrosis
Tissue Repair
- Tissues respond to injury in two stages: inflammation and regeneration
- The ability to regenerate varies among tissues
- Epithelia, connective tissues (except cartilage), and smooth muscle regenerate well
- Skeletal muscle, cardiac muscle, and nervous tissues regenerate poorly, if at all
- Damaged cardiac muscle cells are replaced by fibrous tissue through fibrosis
Skin Repair
- Loss of skin turgor can be caused by dehydration, aging, hormones, and UV radiation
- Excessive distortion of skin from pregnancy or weight gain may cause stretch marks
Aging and the Integumentary System
- Epidermis thins
- Number of dendritic cells decreases
- Vitamin D3 production declines
- Melanocyte and glandular activities decline
- Blood supply to dermis is reduced
- Function of hair follicles declines
- Dermis thins and elastic fiber network shrinks
- Sex-specific hair and body fat distribution fades
- Repair rate slows
Perspiration
- Water is lost from skin in two ways: insensible perspiration (water diffuses across the stratum corneum and evaporates) and sensible perspiration (water excreted by sweat glands)
- Apocrine sweat glands: Found in armpits, around nipples, and in pubic region; secrete products into hair follicles; produce sticky, cloudy secretions that are a nutrient source for bacteria, causing odors
- Eccrine (merocrine) sweat glands: Coiled tubular glands that discharge directly onto the skin surface; widely distributed on body surface; secretions are 99 percent water plus salt, etc.
Functions of Eccrine Sweat Glands
- Cooling the surface of skin to reduce body temperature
- Excreting water and electrolytes
- Providing protection from environmental hazards
Pigmentation
- Melanin: Red-yellow or brown-black pigment produced by melanocytes; stored in intracellular vesicles called melanosomes, which are transferred to keratinocytes; protects skin from UV radiation
- Carotene: Orange-yellow pigment found in orange vegetables; accumulates in epidermal cells, deep dermis, and subcutaneous layer; can be converted to vitamin A
Blood Flow and Oxygenation
- Hemoglobin is bright red when bound to oxygen; when blood vessels dilate from heat, skin reddens; when blood flow to skin decreases, skin pales
- Hemoglobin turns dark red when oxygen is released, which can result in cyanosis (bluish skin)
- Thermoregulation is the main function of sensible perspiration (controlled by the nervous system)
Bone Function
- The skeletal system provides support, mineral and lipid storage, blood cell production, protection, and leverage
Compact vs Spongy Bone
- Compact bone: Dense, strong, and organized into osteons (cylindrical functional units)
- Spongy bone: Lacks osteons, contains red bone marrow (forms blood cells) and yellow bone marrow (stores fat)
Long Bone
- Periosteum: Membrane that covers the outside of bones (except within joint cavities); contains an outer fibrous layer and an inner cellular layer; increases strength of attachments
- Endosteum: Incomplete cellular layer that lines the medullary cavity; active during bone growth, repair, and remodeling; covers trabeculae of spongy bone and lines central canals of compact bone
Intramembranous Ossification
- Develops bones from sheets of connective tissue membranes; involved in the formation of flat bones of the skull, clavicles, and some irregular bones
Exercise Effect on Bone
- Mineral recycling allows bones to adapt to stress
- Heavily stressed bones become thicker and stronger
- Exercise (especially weight-bearing) stimulates osteoblasts
- Bone degenerates quickly (up to one-third of bone mass can be lost in a few weeks of inactivity)
Hormones
- Growth hormone and thyroxine: Stimulate bone growth
- Sex hormones: Estrogen and testosterone stimulate osteoblasts
- Parathyroid hormone and calcitonin: Maintain calcium ion homeostasis
Parathyroid Hormone (PTH)
- Produced by parathyroid glands in the neck
- Increases blood calcium ion levels by:
- Stimulating osteoclast activity (indirectly)
- Increasing intestinal absorption of calcium by enhancing calcitriol secretion by kidneys
- Decreasing calcium excretion by kidneys
Calcitonin
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Produced by C-cells in the thyroid gland
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Decreases blood calcium levels by:
- Inhibiting osteoclasts
- Increasing the amount of calcium excreted in urine
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Levels of both PTH and calcitonin are controlled by blood calcium levels (PTH is released when blood calcium levels are low, calcitonin is released when blood calcium levels are high)
Calcium
- Calcium deposits make bone matrix dense
- Osteocytes (bone cells) are located within lacunae organized around blood vessels
- Canaliculi are narrow passageways that allow for the exchange of nutrients, wastes, and gases
- Periosteum covers the outer surfaces of bones
Bone Development
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Ossification (osteogenesis) is bone formation
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Calcification is the deposition of calcium salts during ossification
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Two forms of ossification:
- Endochondral ossification: Cartilage is replaced by bone
- Intramembranous ossification: Bone develops directly from mesenchyme
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Some human bones grow until about age 25
Functional Classifications of Joints
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Structural Classification: Based on anatomy
- Fibrous
- Cartilaginous
- Bony
- Synovial
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Functional Classification: Based on range of motion
- Synarthrosis: Immovable joint
- Amphiarthrosis: Slightly movable joint
- Diarthrosis: Freely movable joint
Synarthrosis (immovable joint)
- Very strong, edges of bones may touch or interlock; may be fibrous or cartilaginous
- Four types:
- Suture: Found between bones of the skull
- Gomphosis: Attachment of a tooth to its socket
- Synchondrosis: Bones are connected by hyaline cartilage (example: epiphyseal plates)
- Synostosis: Bones are fused together, forming a single bone
Synovial Joints (diarthroses)
- Freely movable joints found at the ends of long bones
- Joint capsule (articular capsule): Surrounds the joint, contains synovial membrane
- Synovial fluid: Fills the joint cavity, produced by the synovial membrane
- Articular cartilage: Covers articulating surfaces, prevents direct contact between bones
Stabilizing Synovial Joints
- Cartilages and fat pads: Cushion and protect the joint
- Ligaments: Connect bones, provide strength and stability
- Tendons: Connect muscles to bones, provide support and movement
- Bursae: Small pockets of synovial fluid that cushion areas where tendons or ligaments rub
Factors that Stabilize Synovial Joints
- Collagen fibers of joint capsule and ligaments
- Shapes of articulating surfaces and menisci
- Other bones, muscles, or fat pads
- Tendons attached to articulating bones
Types of Synovial Joint Movements
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Planes of Movement:
- Monaxial: Movement in one plane (example: elbow)
- Biaxial: Movement in two planes (example: wrist)
- Triaxial: Movement in three planes (example: shoulder)
Types of Synovial Joints
- Saddle joint: Articular faces fit together like a rider in a saddle (biaxial)
- Pivot joint: Rotation only (monaxial)
- Ball-and-socket joint: Round head in a cup-shaped depression (triaxial)
Sprain
- A ligament with torn fibers
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Description
Test your knowledge about epithelial tissue, its types, and functions with this quiz. Learn the differences between covering, lining, and glandular epithelia, and their roles in the body. Explore both simple and stratified cuboidal epithelia as well as glandular structures.
