Hair, Glands, Nails, Bone (Osteology) and Joints - Vocabulary Flashcards
Integumentary System: Hair and Nails
Hair anatomy overview
- Shaft: the part of the hair that extends beyond the skin (epidermis). Length varies among individuals.
- Root: the portion of the hair that penetrates through the epidermis and dermis down to the subcutaneous layer; the root is below the skin surface.
- Follicle: the layer surrounding the root; site of mitosis; hair growth occurs as hair cells divide within the follicle and push upward.
- Growth dynamics: hair grows from the root/follicle via mitosis; shaft lengthens as new cells push the older cells upward.
- Shaving vs plucking: shaving removes the shaft above the skin; plucking removes the follicle/root, which can delay regrowth.
Glands and associated structures in the dermis
- Sebaceous glands (oil glands): produce sebum (oil) that lubricates and waterproofs hair and skin. Oil travels up the hair follicle and erupts onto the shaft.
- Functions: lubrication, moisture retention; oil helps waterproof but can contribute to acne if ducts become plugged or infected.
- Distribution: present widely across the body but not on palms of hands and soles of feet.
- Arrector pili muscle: smooth muscle band attached to hair follicles; contraction causes hair to stand up (goosebumps) and contributes to warmth via minor heat production.
- Sweat glands (pseudoriferous glands): two main types
- Eccrine glands: not attached to hair follicles; open directly to the skin surface; widely distributed (including palms and soles); primary role in thermoregulation via perspiration.
- Apocrine glands: attached to hair follicles; found in axillary (armpit), areolar (chest), and pubic regions; sweat interacts with skin bacteria to produce body odor.
- Ceruminous glands: specialized glands in the external auditory meatus (ear canal) that secrete cerumen (earwax); serves protection, moisture retention, and debris collection.
- Lipids and oil glands are ducts that can become clogged, leading to acne or pimples; infection can occur if ducts become blocked.
Nails: anatomy and growth
- Nail body: the visible portion of the nail.
- Free edge: the part that extends beyond the distal tip of the finger or toe.
- Nail root: portion buried under the skin folds; growth originates from the nail matrix.
- Nail matrix: cells surrounding the root that undergo mitosis to form the nail; growth pushes the nail outward.
- Lunula: the pale half-moon-shaped area at the proximal end of the nail body; thickness of the epidermis obscures underlying blood vessels.
- Eponychium (cuticle): the tissue that adheres the skin to the nail body; a hangnail occurs if the cuticle lifts and can lead to infection.
- Nail bed: underlying skin beneath the nail body (not explicitly named in all slides but part of nail anatomy).
- Growth and maintenance: matrix cells divide to form new nail plate; nails serve protective and functional roles for digits.
Quick connections and practical implications
- Skin layers: epidermis (outermost), dermis (contains glands and hair follicles), subcutaneous layer (fat/areolar tissue).
- Glycally, hair and nails rely on the same basic processes of cell division and keratinization in their respective structures.
- Common questions: what structures are in the hair shaft vs. root; what glands are associated with hair follicles; why sweating helps cool the body; what protects the ear canal.
Osteology: Bone Basics and Structure
Overview and key numbers
- Osteology: the study of bone structure, treatment of bone disorders, and related aspects.
- Humans have 206 bones in the adult skeleton; at birth, there are about 270, which fuse over time to yield 206.
- Bone serves multiple essential functions: support, protection, movement, mineral storage, blood cell formation, and energy storage.
- Mineral storage: calcium and phosphate are major minerals stored in bone; ongoing remodeling involves crystallization and release of these minerals. Other trace minerals (e.g., boron) contribute to bone health.
- Blood cell production: red bone marrow produces red and white blood cells and platelets.
- Energy storage: yellow bone marrow stores fat as an energy reserve.
- Bone is a living, dynamic tissue capable of growth, remodeling, and healing.
Major functions of bone
- Support: provides a framework for the body and attachment points for muscles.
- Protection: encases vital organs (e.g., brain protected by skull, lungs and heart protected by thorax, spine protected by vertebrae).
- Movement: muscles attach to bones via tendons; bones act as levers when muscles contract.
- Mineral storage: calcium and phosphate minerals are deposited or released as needed.
- Blood cell production: red marrow within certain bones produces blood cells.
- Energy storage: yellow marrow stores adipose tissue.
Bone is organized into two principal tissues
- Compact bone (dense, hard): low porosity; arranged in osteons; provides strength and protection.
- Spongy bone (cancellous or trabecular): porous, with trabeculae; contains red marrow; lighter and supports metabolic processes.
- Adaptation: compact bone covers spongy bone; spongy bone is present in ends of long bones and in flat bones.
Long bones: key structural terms
- Diaphysis: the shaft or tubular middle portion of a long bone.
- Epiphysis: the ends of a long bone.
- Metaphysis: the region between the diaphysis and the epiphysis.
- Epiphyseal plate (growth plate): cartilaginous region between diaphysis and epiphysis that allows lengthwise bone growth during development.
- Epiphyseal line: when growth ends, the plate ossifies into a line.
- Articular cartilage: thin layer of hyaline cartilage covering the ends of epiphyses at joints.
- Periosteum: tough outer membrane that covers bone except where articular cartilage is present.
- Endosteum: inner membrane lining the medullary (marrow) cavity.
- Medullary (marrow) cavity: hollow center of the diaphysis; contains yellow marrow in adults.
- Red bone marrow: located mostly in the epiphyses of long bones in adults; site of blood cell production.
- Yellow bone marrow: stores fat; energy reserve.
Bone growth and aging considerations
- Growth occurs at the metaphysis via the epiphyseal plate (cartilaginous). Growth continues until roughly age 25, when the plate ossifies to form the epiphyseal line.
- Hormones influence growth: growth hormone, estrogen, and testosterone contribute to bone growth and maturation.
- Osteoblasts build bone; osteoclasts break down bone; osteoprogenitor cells (osteogenic cells) are stem cells that differentiate into osteoblasts.
- Balance between osteoblast and osteoclast activity is crucial for healthy bone density.
- Post-menopause, decreased estrogen can lead to increased osteoclast activity and osteoporosis risk.
Bone cell types and their roles
- Osteoprogenitor (osteogenic) cells: stem cells that differentiate into osteoblasts.
- Osteoblasts: build new bone (bone-forming cells). They reside on the bone surface.
- Osteocytes: mature bone cells that maintain bone tissue; reside in lacunae within the bone matrix.
- Osteoclasts: break down old bone tissue; important for remodeling and calcium/phosphate release.
Compact bone anatomy (Haversian system)
- Osteon (Haversian system): the basic structural unit of compact bone.
- Central (Haversian) canal: runs through the center of an osteon and contains blood vessels and nerves.
- Lamellae: concentric rings of mineralized matrix surrounding the central canal.
- Lacunae: small pockets within the lamellae that house osteocytes.
- Canaliculi: tiny channels connecting lacunae and allowing communication and nutrient exchange between osteocytes.
- Periosteum and endosteum play roles in bone growth and repair.
- Osteons provide strength and allow nutrient diffusion through the dense matrix.
Spongy bone anatomy
- Trabeculae: lattice-like network in spongy bone; provides some strength while maintaining lighter weight.
- Red bone marrow is housed within trabeculae-rich regions of spongy bone, enabling hematopoiesis.
- Spongy bone is found in the epiphyses of long bones and in flat bones (e.g., skull, pelvis).
Bone shapes and their classifications
- Long bones: longer than they are wide (e.g., femur, humerus, radius, ulna).
- Short bones: approximately equal in length and width (e.g., carpals, tarsals).
- Flat bones: broad surfaces for muscle attachment and protection (e.g., sternum, ribs, skull bones).
- Irregular bones: diverse shapes (e.g., vertebrae).
- Sutural (wormian) bones: small bones within sutures of the skull.
- Sesamoid bones: embedded within tendons; common example is the patella (kneecap). Other small sesamoids can occur within the hands and feet.
Joints and classifications (brief overview)
- Fibrous joints: no joint cavity; limited or no movement; connected by dense connective tissue (e.g., sutures in the skull, syndesmosis).
- Cartilaginous joints: no or limited movement; bones joined by cartilage (e.g., synchondrosis between epiphyseal plate; pubic symphysis).
- Synovial joints: freely movable joints with a joint cavity and synovial fluid; include various subtypes for different movement ranges.
Synovial joints: movement and range of motion (ROM)
- ROM: range of motion; the extent of movement in a joint.
- Gliding joints: sliding movements between flat surfaces (e.g., carpal bones of the wrist, tarsal bones of the ankle).
- Flexion and extension: decrease and increase of an angle, respectively (e.g., elbow, knee).
- Abduction and adduction: moving away from or toward the midline of the body.
- Circumduction: a combination of flexion, extension, abduction, and adduction, producing a circular motion.
- Rotation: turning around a longitudinal axis (e.g., neck, forearm pivot).
- Inversion and eversion: turning the sole of the foot inward or outward; involves foot muscles.
- Supination and pronation: rotation of the forearm/hand; palm up (supination) vs palm down (pronation).
- Elevation and depression: movements in a superior and inferior direction (e.g., shoulders).
- Plantarflexion and dorsiflexion: movements at the ankle; plantarflexion points toes downward; dorsiflexion lifts the foot upward.
Major joint types and examples
- Synovial joints: include gliding (carpal/tarsal), hinge (elbow/knee), pivot (radius/ulna, atlantoaxial joint), condyloid (radius/wrist), saddle (thumb), ball-and-socket (hip, shoulder).
- Fibrous joints: sutures, syndesmosis, gomphosis (tooth sockets).
- Cartilaginous joints: synchondrosis (epiphyseal plate -> line in adulthood), symphysis (pubic symphysis).
Axial and Appendicular skeletons
- Axial skeleton: 80 bones; midline structures
- Skull, vertebral column, sternum (breastbone), ribs, hyoid bone
- Hyoid bone: U-shaped bone in the throat, completely surrounded by muscle, not directly articulating with other bones.
- Appendicular skeleton: 126 bones; limbs and girdles
- Pectoral girdle: clavicle and scapula
- Upper limbs: humerus, radius, ulna, carpals, metacarpals, phalanges
- Pelvic girdle: os coxa (hip bones)
- Lower limbs: femur, tibia, fibula, tarsals, metatarsals, phalanges
Skull landmarks and landmark terms (high-yield for exams)
- Frontal bone: forehead; key landmarks include the supraorbital foramen (above the orbit) and frontal sinus (air cavity within the bone).
- Parietal bones: located on the top of the skull; generally labeled as left and right.
- Temporal bones: landmarks include the mastoid process (behind the ear) and the styloid process (a sharp projection behind the ear); external auditory meatus (ear canal opening).
- Occipital bone: landmarks include the foramen magnum (large hole for the spinal cord), occipital condyles (rounded knobs that articulate with C1), external occipital protuberance (bump at the back of the skull).
- Sphenoid bone: contains several important features
- Sella turcica (pituitary gland seat)
- Foramina: foramina rotundum, ovale, spinosum, and lacerum (three side holes in a row near the center; lacerum more medially located).
- Sphenoid sinus (paranasal sinus) within the bone.
- In the orbit, contributes to superior and inferior orbital fissures; optic foramen is the opening for the optic nerve.
- Ethmoid bone: middle between frontal and nasal regions; contains the cribriform plates (olfactory foramina) for smell; perpendicular plate forms part of the nasal septum; superior and middle nasal conchae; contributes to the orbit and nasal cavity.
- Fontanels: fetal/infant connective tissue gaps between cranial bones; anterior fontanelle (frontal), posterior fontanelle (occipital); these fuse over the first year or two to become sutures.
Paranasal sinuses
- Air-filled spaces within skull bones (e.g., frontal sinus, sphenoid sinus); lined with mucosa.
- Purpose: lighten the skull, humidify and warm air, add resonance to voice; infections can cause facial pressure and headache.
Foramina, fossae, canals, and other bone features (glossary)
- Foramen: round hole through which vessels or nerves pass.
- Fossa: a shallow depression or hollow area that often houses a muscle.
- Meatus: a canal or passage through a bone.
- Sulcus: a groove or furrow for nerves or vessels.
- Condyle: rounded end that forms a joint.
- Epicondyle: projection above a condyle.
- Crest/linea: ridges; prominences for muscle attachment.
- Process: any projection or outgrowth on a bone.
- Tubercle/tuberosity: small/roughened projections for muscle/tendon attachment.
Practical notes for lab and exams
- Focus on the major landmarks listed for skull bones (frontal, parietal, temporal, occipital) and the key features on each (foramina, sinuses, processes).
- Recognize the difference between paranasal sinuses and other air-filled spaces.
- Understand the difference between a “hole” (foramen) and a “notch/ groove” (fossa, sulcus) as well as a “cavity” and a “canal.”
Quick connections to broader topics
- The axial skeleton houses the central nervous system and thoracic organs; the appendicular skeleton supports movement and locomotion.
- Growth and aging of bones tie into nutrition (calcium, phosphate, vitamin D), hormones (growth hormone, estrogen, testosterone), and health conditions (osteoporosis, osteoarthritis).
- The dynamic nature of bone remodeling links to clinical issues like fracture healing and osteoporosis management.
Summary of key terms to memorize (high-yield)
- Osteon, central canal, lamellae, lacunae, canaliculi, osteoblasts, osteocytes, osteoprogenitor cells, osteoclasts
- Diaphysis, epiphysis, metaphysis, epiphyseal plate/line, periosteum, endosteum, medullary cavity, red/yellow marrow
- Compact bone vs. spongy bone; trabeculae
- Frontal bone, supraorbital foramen, frontal sinus; parietal bones; temporal bone (mastoid process, styloid process, external auditory meatus); occipital bone (foramen magnum, occipital condyles, external occipital protuberance); sphenoid bone (sella turcica, foramina rotundum/ovale/spinosum/lacerum, optic foramen, sphenoid sinus); ethmoid bone (cribriform plate, perpendicular plate, superior/middle nasal conchae, olfactory foramina)
- Fontanels (anterior/posterior), sutures (frontal-sagittal).
Note on a few clinical correlations mentioned in class
- Estrogen decline post-menopause can lead to osteoclast-dominant bone resorption and higher osteoporosis risk.
- Calcium and phosphate balance requires dietary calcium, phosphate, and absorption aided by vitamin D; imbalances can contribute to kidney stones if minerals crystallize improperly.
- Sinuses can become infected, leading to facial pressure and congestion.