Human Anatomy & Physiology - The Skeleton: Part A

These flashcards cover key terms and concepts from the lecture on human anatomy focusing on the skeleton, paranasal sinuses, and vertebral column.

Paranasal Sinuses

Mucosa-lined, air-filled spaces that help lighten the skull, enhance voice resonance, warm and humidify air, and are found in frontal, sphenoid, ethmoid, and maxillary bones.

Frontal Sinus

One of the paranasal sinuses located in the frontal bone, involved in voice resonance and lightening the skull.

Ethmoidal Air Cells

A group of small air-filled spaces within the ethmoid bone that contribute to the structure of the nasal cavity.

Sphenoidal Sinus

An air-filled space located within the sphenoid bone that is part of the paranasal sinus system.

Maxillary Sinus

The largest of the paranasal sinuses located in the maxilla, which plays a role in voice resonance and air humidification.

Vertebral Column

A flexible curved structure consisting of 26 irregular bones (vertebrae) that transmit the weight of the trunk to the lower limbs and protect the spinal cord.

Cervical Vertebrae

Seven vertebrae of the neck (C1-C7) that make up the upper section of the vertebral column.

Thoracic Vertebrae

Twelve vertebrae (T1-T12) that comprise the middle part of the vertebral column, associated with the thoracic cage.

Lumbar Vertebrae

Five larger vertebrae (L1-L5) in the lower back that support the weight of the body.

Scoliosis

An abnormal lateral curve of the spine.

Kyphosis

An exaggerated thoracic curvature of the spine, often referred to as hunchback.

Lordosis

An accentuated lumbar curvature of the spine, commonly referred to as swayback.

Hyoid Bone

A U-shaped bone in the neck that is not directly articulated with any other bone and serves as a movable base for the tongue.

Secondary Curvatures

Curvatures of the spine that form as a child develops, including the convex anterior cervical and lumbar curvatures.

Primary Curvatures

The thoracic and sacral curvatures of the spine that are present from birth, giving the spine a C shape.

Hyaline Cartilage Locations

Articular cartilages, costal cartilages, respiratory cartilages, nasal cartilages.

Elastic Cartilage Locations

External ear (pinna), epiglottis.

Fibrocartilage Locations

Menisci of the knee, intervertebral discs, pubic symphysis.

Long Bones

Considerably longer than wide (e.g., humerus, femur, tibia).

Short Bones

Roughly cube-shaped (e.g., carpals, tarsals).

Flat Bones

Thin, flattened, and usually curved (e.g., sternum, scapulae, skull bones).

Irregular Bones

Complicated shapes, don't fit other categories (e.g., vertebrae, hip bones).

Functions of Bones

Support, Protection, Movement, Mineral and Growth Factor Storage, Blood Cell Formation (Hematopoiesis), Triglyceride (Fat) Storage, Hormone Production (Osteocalcin).

Compact Bone Structure

Dense outer layer, organized into osteons (Haversian systems).

Spongy Bone Structure

Trabeculae forming an open network, spaces filled with red or yellow bone marrow.

Diaphysis

The shaft of a long bone, composed of compact bone surrounding a medullary cavity.

Epiphyses

The bone ends (proximal and distal) of a long bone, consisting of compact bone externally and spongy bone internally.

Periosteum

Double-layered membrane covering the external bone surface (except joints), with outer fibrous layer and inner osteogenic layer.

Endosteum

Delicate connective tissue membrane covering internal bone surfaces, containing osteogenic cells.

Epiphyseal Plate (Growth Plate)

Disc of hyaline cartilage in growing bones that lengthens the bone during childhood.

Metaphysis

Region where diaphysis and epiphysis meet, containing the epiphyseal plate in growing bones.

Articular Cartilage

Hyaline cartilage covering joint surfaces of epiphyses, cushioning and absorbing stress.

Red Bone Marrow

Hematopoietic tissue, produces blood cells. Found in axial skeleton, girdles, and proximal humerus/femur in adults.

Yellow Bone Marrow

Adipose tissue storage. Found in medullary cavity of long bones in adults.

Osteogenic Cells

Mitotically active stem cells in periosteum and endosteum, differentiate into osteoblasts or bone-lining cells.

Osteoblasts

Bone-forming cells, secrete osteoid (bone matrix). Become osteocytes when trapped.

Osteocytes

Mature bone cells in lacunae; monitor and maintain bone matrix, act as stress sensors.

Bone-Lining Cells

Flat cells on bone surfaces not remodeling; maintain matrix. (Periosteal cells externally, Endosteal cells internally).

Osteoclasts

Giant, multinucleate cells that resorb (break down) bone matrix.

Osteon (Haversian System)

Structural unit of compact bone; tiny weight-bearing pillar.

Central (Haversian) Canal

Runs through core of osteon, contains blood vessels and nerve fibers.

Perforating (Volkmann's) Canals

Connect blood and nerve supply of periosteum to central canals and medullary cavity.

Lamellae

Concentric rings of bone matrix within an osteon, resist twisting stresses.

Lacunae

Small cavities at lamellae junctions, housing osteocytes.

Canaliculi

Hairlike canals connecting lacunae, allowing osteocyte communication and nutrient exchange.

Organic Components of Bone (Osteoid)

Approximately one-third of matrix, includes ground substance and collagen fibers; contributes to flexibility and tensile strength.

Inorganic Components of Bone (Mineral Salts)

Mainly hydroxyapatites (calcium phosphates); accounts for bone's hardness and compression resistance.

Endochondral Ossification

Forms most bones inferior to the skull (except clavicles) using a hyaline cartilage model.

Primary Ossification Center

First area of bone development, at the center of the diaphysis.

Secondary Ossification Centers

Areas of bone development appearing in the epiphyses, typically after birth.

Intramembranous Ossification

Forms cranial bones of the skull and clavicles directly from fibrous connective tissue membranes.

Growth in Length (Longitudinal Growth)

Occurs at the epiphyseal plate via endochondral ossification, pushing epiphysis away from diaphysis.

Growth in Width (Appositional Growth)

Occurs throughout life, osteoblasts add bone to external surface while osteoclasts remove bone from internal surface, widening medullary cavity.

Bone Remodeling

Continuous process of bone deposition (osteoblasts) and resorption (osteoclasts); controlled by hormones and mechanical forces.

Ca^{2+} Homeostasis

Maintaining blood calcium levels between 9-11 mg/dL.

Parathyroid Hormone (PTH) Influence

Released when Ca^{2+} levels are low; stimulates osteoclasts, enhances kidney reabsorption, activates vitamin D for intestinal absorption, thus increasing blood Ca^{2+}.

Calcitonin Influence

Lowers blood Ca^{2+} by inhibiting osteoclast activity and stimulating Ca^{2+} uptake by bone matrix (minor role in adults).

Wolff's Law

Bone grows or remodels in response to demands placed on it; thickens with stress, weakens without.

Comminuted Fracture

Bone fragments into three or more pieces, common in older people.

Compression Fracture

Bone is crushed, common in porous bones subjected to trauma.

Spiral Fracture

Ragged break from excessive twisting forces, common sports fracture.

Epiphyseal Fracture

Epiphysis separates from diaphysis along epiphyseal plate, occurs where cartilage cells are dying.

Depressed Fracture

Broken bone portion pressed inward, typical of skull fracture.

Greenstick Fracture

Bone breaks incompletely, only one side breaks, other bends; common in children.

Osteomalacia (Adult Rickets)

Inadequate bone mineralization in adults, leading to soft, weak bones due to insufficient Ca^{2+} or vitamin D deficiency.

Rickets (Childhood Osteomalacia)

Inadequate bone mineralization in children, causing bowed legs and deformities due to insufficient Ca^{2+} or vitamin D deficiency.

Difference: Osteomalacia vs. Osteoporosis

Osteomalacia is a problem with bone mineralization (soft bones), while Osteoporosis is a problem with bone mass (porous, fragile bones).

Osteoporosis

Bone resorption outpaces bone deposition, making bones porous and prone to fractures.

Osteoporosis Risk Factors

Age, gender (postmenopausal women), heredity, nutritional deficiencies (calcium, vitamin D), sedentary lifestyle, smoking, excessive alcohol, certain medical conditions/medications.

Osteoporosis Treatment

Calcium/Vitamin D supplements, weight-bearing exercise, bisphosphonates, SERMs, Denosumab, Teriparatide.

Paget's Disease

Chronic disease of excessive and haphazard bone deposit/resorption, resulting in weakened, enlarged bone deformities; cause unknown (possibly viral, genetic).