Exam 3 Anatomy Quizlet

How many bones are there at birth versus in an adults

270 bones at birth; 206 bones in a typical adult.

Three types of cartilage

Hyaline cartilage, elastic cartilage, and fibrocartilage.

Where is hyaline cartilage?

Articular cartilage: Covers joint surfaces where bones move across each other, Costal Cartilage: connects true ribs to sternum, nose

Hyaline cartilage function

Helps reduce friction at joints and provides structural support.

Elastic cartilage locations

External ear and epiglottis.

Elastic cartilage function

Highly flexible due to elastic fibers

Fibrocartilage main function

Shock absorption

Fibrocartilage locations

Intervertebral discs, pubic symphysis, and menisci of knees.

Perichondrium structure

Layer of dense irregular connective tissue surrounding all cartilage.

Compact/Dense/Cortical bone location

External layer of bones surrounding the medullary cavity.

Compact bone appearance

Dense, smooth, solid white osseous tissue.

Spongy/Cancellous/Trabecular bone location

Internal layer of bones surrounded by compact bone and filled with trabeculae

Where is spongy bone found in long bones?

the epiphyses and just outside medullary cavity (thin layer)

What is the architecture of spongy bone?

Appears poorly organized and develops due to stress lines. Has irregular arrangement of lamellae and osteocytes

Spongy bone nutrient delivery

Nutrients diffuse directly through canaliculi from endosteum space.

Structure of short, flat, and irregular bones

Spongy bone sandwich between two outer layers of compact bone.

Structure of Long Bones

Epiphysis, Epiphyseal Line, Metaphysis, Diaphysis, Metaphysis, Epiphyseal line, Epiphysis

Epiphysis

Expanded head at each end of a long bone that strengthens joints, increases surface area, and provides attachment site

Diaphysis

Elongated shaft of a long bone housing the medullary cavity and provides leverage

Epiphyseal line

Remnant of the epiphyseal plate (growth plate) in adult bone.

Long bone examples

Humerus, radius, femur, tibia, metacarpals, metatarsals, phalanges.

Long bone function

Movement

Short bone shape and examples

Roughly cube-shaped; carpals (wrist) and tarsals (ankle).

Flat bones

thin, flattened (usually curved)

Flat bone examples

Sternum, scapulae, ribs, hip bones, most cranial bones.

Flat bone functions

Provides protection

Irregular bone function and examples

Vertebrae for support and protection

Sesamoid bone definition

Bone formed within a tendon in response to strain.

Largest sesamoid bone

Patella (kneecap).

Sutural bones

Extra bone islands that form within skull joints (sutures).

Osteogenic (osteoprogenitor) cells

Stem cells that differentiate into osteoblasts.

Osteogenic cells location

Deep inner layer of periosteum and marrow.

Osteoblasts

Bone-forming cells that synthesize osteoid and promote mineralization in osteogenic layers

Osteoblast locations

Growing portions of bone including periosteum and endosteum

Osteocytes

Mature bone cells trapped in lacunae maintaining matrix mineral density; 90-95% of all bone cells

Osteoclasts

Large, multi-nucleated bone-resorbing cells which ruffled edge for increased surface area

Osteoclast location

Bone surfaces at sites of old, injured, or unneeded bone.

Bones formed by intramembranous ossification

Flat bones of skull, parts of clavicle, scapula, and mandible.

Intramembranous ossifcation Step 1

Mesenchymal cells (stem cells) cluster around a vessel and become osteoblasts. Osteoblasts secrete osteoid and an ossification center forms in fibrous connective tissue

Intramembranous ossifcation Step 2

Osteoblasts grow and continue to secrete osteoid. Trapped osteoblasts now become osteocytes

Intramembranous ossifcation Step 3

Osteoid continues to form around vessels forming an immature spongy bone, mesenchyme adheres to the external surface and becomes the periosteum

Intramembranous ossifcation Step 4

Immature spongy bone near the periosteum is remodeled and replaced with compact bone, central immature spongy bone matures

Endochondal Ossification Step 1

Mesenchymal cells specialize into osteoblasts, perichondrium becomes periosteum, osteoblasts secrete osteoid creating a bone collar, chondrocytes left within hypertrophy and become primary ossification center

Endochondral Ossification Step 2

Chondrocytes from the primary ossification center ossify surrounding cartilage, chondrocytes die and matrix begins to dissolve, cavities are now formed within the model, remaining cartilage (ends) are healthy and growing rapidly to elongate the model

Endochondral Ossification Step 3

Cavities are invaded by the periosteal bud, osteoclasts partially erode the cartilage matrix, osteoprogenitor cells become osteoblasts (spongy bone formation!!)

Endochondral Ossification Step 4

Osteoclasts break down the newly formed spongy bone and open the cavity, the epiphyses stay as cartilage ends through birth (growing rapidly), after birth secondary ossification centers develop at epiphyses

Endochondral Ossification Step 5

Secondary ossification mimics that of primary except the spongy bone remains and no cavity is formed, the space between the diaphysis and epiphysis is the epiphyseal plate and is hyaline cartilage

How many secondary ossification centers are there for different types of bones?

Long bones of arms/legs have at least 2 secondary ossification centers, Shorter long bones + short bones have 1, Irregular have multiple

Interstitial growth (Postnatal Growth)

Postnatal growth in bone length occurring at epiphyseal plate.

Interstitial growth zone 1: Proliferation

Chondrocytes rapidly divide and older chondrocytes get pushed down

Interstitial growth zone 2: Hypertrophic

Older chondrocytes enlarge lacunal implode leaving empty spaces

Interstitial growth zone 3: Calcification

Surrounding matrix calcifies, chondrocytes die

Interstitial growth zone 4: Ossification

Chondrocytes die, Osteoblasts promote ossification and deposit concentric lamellae

Appositional growth Postnatal growth) definition

Postnatal growth in bone diameter (thickness/width) that occurs through deposition of new tissue at the surface

Appositional growth process

Osteoblasts under periosteum build bone while osteoclasts in endosteum resorb bone.

Appositional growth balance

Osteoblast activity slightly exceeds osteoclast activity, expanding bone width.

Organic components of bone matrix

Cells and osteoid (unmineralized matrix from osteoblasts)

Organic components of bone matrix function

-gives bone tensile strength by resisting stretching

-contributes to bone flexibility

inorganic components of the bone matrix

Mineral salts (Calcium, phosphate)

Inorganic bone matrix function

Provides hardness and compressional strength.

Endosteum definition

Delicate membrane lining internal bone cavities and canals and contains same cells as inner periosteum (osteogenic)

Endosteum locations

Marrow cavity, surfaces of spongy bone, canal system

Periosteum Function

Attachment site for tendons

Periosteum outer layer structure

Dense irregular connective tissue with irregular collagen fibers.

Periosteum outer layer function

Withstands multi-directional pulling forces

Periosteum inner layer contents

Contains bone-forming cells that add to the surface of bone

Where periosteum is ABSENT

Over articular cartilage surfaces at joints.

Which bony landmarks are articulations?

Condyle, Facet, Head

Condyle

Rounded knob that articulates with another bone (e.g., occipital condyle).

Facet

Smooth, flat, slightly concave or convex articular surface (e.g., articular facets of vertebrae).

Head

Prominent expanded end of a bone (e.g., head of femur).

Crest

Narrow ridge of bone (e.g., iliac crest).

Epicondyle

Expanded region proximal to a condyle (e.g., medial epicondyle of femur).

Line

Slightly raised, elongated ridge (e.g., nuchal line of skull).

Process

Any prominent bony projection (e.g., mastoid process).

Protuberance

Bony outgrowth or protruding part (e.g., mental protuberance).

Ramus

Branching arm or extension of a bone (e.g., ramus of mandible).

Spine

Sharp, slender, or narrow process (e.g., mental spine of mandible).

Trochanter

Two massive processes unique to the femur.

Tubercle

Small, rounded projection (e.g., greater tubercle of humerus).

Tuberosity

Rough, elevated surface (e.g., tibial tuberosity).

Alveolus

Deep pit or socket (e.g., tooth socket).

Fossa

Shallow, broad, or elongated basin (e.g., mandibular fossa).

Fovea

Small, distinct pit (e.g., fovea capitis of femur).

Sulcus

Groove for a tendon, nerve, or blood vessel (e.g., intertubercular sulcus).

Canal

Tubular passage or tunnel through bone (e.g., auditory canal).

Fissure

Slit-like opening through a bone (e.g., orbital fissure).

Foramen

Round or oval hole through a bone (e.g., foramen magnum).

Sinus

Air-filled cavity within a bone (e.g., frontal sinus).

Percentage of body's calcium stored in bone

99% of total calcium.

Hypocalcemia definition & symptom

Low blood calcium level; causes increased neuronal excitability and muscle tremors.

Hormone released during hypocalcemia

Parathyroid Hormone (PTH).

Parathyroid Hormone effects on osteoclasts/osteoblasts

Increases osteoclast activity (bone absorption); decreases osteoblast activity

Parathyroid Hormone effect on kidney excretion

Increases urinary phosphate excretion which prevents hydroxyapatite which causes decreased bone deposition; decreases urinary calcium excretion.

Hypercalcemia definition & symptoms

High blood calcium level; causes decreased neuronal excitability, fatigue, sluggish reflexes, rare cardiac arrest

Hormone released during hypercalcemia

Calcitonin (secreted by thyroid gland).

Calcitonin action mechanism hypercalemia

Causes decreased osteoclast activity which causes decreased bone resorption, Causes increased osteoblast activity which causes more bone deposition

Parathyroid Hormone

Stimulates the osteoclasts to promote bone resorption, Promotes calcium reabsorption by the kidneys, Promotes final step of calcitriol(vitamin D) synthesis in the kidneys, Inhibits collagen synthesis by inhibiting osteoblasts

Calcitriol (Active Vitamin D) functions

Promotes intestinal absorption of Ca2+ and phosphate; reduces urinary excretion of both; promotes both resorption and mineralization; stimulates osteoclast activity

Cortisol effect on bone

Inhibits osteoblasts; excess (Cushing's) stimulates osteoclasts causing osteoporosis.