Animal Skeleton Quiz

General Anatomy - Osteology

• Osteology is the study of bones
• Objectives include:
  • Classification of the skeleton
  • Classification of bones
  • Bone structure
  • Blood supply of bones
  • Nerves of bones
  • Chemical and physical properties of bones
  • Bone growth
  • Function of the skeleton
  • Descriptive terms of the skeletal system

Skeleton

• Skeleton is the framework of hard structures (bones and cartilages) that support and protect soft tissues in animals
• Term "skeleton" comes from a Greek word meaning "dried up"
• All bones and articulations of the body make up the passive part of the body

Classification of the Skeleton

• Exoskeleton: Located externally, derived from ectoderm. Examples include shells of invertebrates, scales of fish, shields of turtles, feathers, hair, and hoofs of vertebrates.
• Endoskeleton: Embedded in the soft tissues

Classification of the skeleton (B)

• Axial skeleton: Includes the skull, vertebral column, ribs, and sternum
• Appendicular skeleton: Includes bones of the thoracic and pelvic limbs

Classification of the skeleton (3)

• Visceral/splanchnic skeleton: Certain bones developed within soft organs. Examples include:
  • Os penis of the dog
  • Os cordis in ruminant hearts
  • Ossa diaphragmatica in camel diaphragms
  • Entoglossal bone in bird tongues

Phylogenetic Classification of the Skeleton

• Membranous skeleton: Characteristic of invertebrates with membrane or connective tissue (no hard skeleton).
• Cartilaginous skeleton: Found in cartilaginous fish.
• Bony skeleton: Found in higher vertebrates with bony structures

Classification of the Bones (A)

• Bones classified by location: head, neck, trunk, limbs, and tail

Classification of the Bones (B-1)

• Tubular bones: Composed of compact and spongy substances, forming a tube with a cavity
• Example: long bones

Bone Structure (3)

• Bone consists of an external shell of dense compact substance (cortex), containing loosely arranged spongy substance
• Shaft of long bones is hollowed to form the medullary cavity

Structure of a Long Bone (diagram)

• Diaphysis (shaft): Contains compact bone and a medullary cavity.
• Metaphysis: Junction zone between the diaphysis and epiphysis. Contains the epiphyseal plate during growth.
• Epiphysis: Ends of the bone, primarily composed of spongy bone, covered with articular cartilage.

Long Tubular Bones (A)

• Long, cylindrical bones (e.g., femur, humerus)
• Extend in one direction
• Consist of a shaft (diaphysis)
• Two extremities (epiphyses)
• Medullary cavity

Short Tubular Bones (B)

• Short bones, yet tubular
• Example: phalanges

Reduced Long Tubular Bones (C)

• Incomplete development
• Long bones, but lack or have a reduced medullary cavity
• Example: metacarpal and metatarsal bones; fibula and ulna of horses

Short Bones (2)

• Short, partially smooth-surfaced
• Primarily found in joints to aid mobility
• Mostly spongy substance, with a thin layer of cortical bone
• Example: carpal bones

Flat Bones (3)

• Plate-like, extending in two dimensions
• Composed of two layers of compact bone enclosing a small amount of spongy substance
• Example: bones of the cranium

Irregular Bones (4)

• Small, irregular surface
• Located mainly in midline of the skeleton
• Have projections for muscular attachments
• Example: vertebrae

Pneumatic Bones (5)

• Bones with air spaces (sinuses) instead of spongy or marrow
• Lined with mucous membranes
• Examples: frontal and maxillary bones (some)

Sesamoid Bones (6)

• Small, seed-like bones
• Reduce friction between tendons and bones
• Change direction of tendon pull
• Example: patella, navicular bone

Chemical Composition and Physical Properties of Bone (6)

• Bone is a mineralized connective tissue
• Primarily composed of inorganic salts and organic matter (ratio of approximately 1:2)
• Organic matter: Includes bone cells, ossein, collagen fibers, intercellular substance; gives bone toughness and elasticity
• Inorganic matter: Predominantly calcium phosphate (85%), followed by calcium carbonate (10%); provides hardness

Color of the Bone

• Fresh bone is yellowish-white
• Boiled and bleached bone is white
• Exposure to acid (e.g., HCl) dissolves calcium phosphate salts. The organic matter remains, retaining the bone's shape but making the bone soft and elastic

Bone Burning

• Burning removes organic matter
• Inorganic material remains, maintaining the bone's shape, but reduced elasticity (and thus, increased fragility)

Bone Growth (7)

• Flat bones: Enlarge through continued ossification at margins of connective tissue
• Long bones: Epiphyseal cartilage remains between epiphysis and diaphysis. It is replaced by bone after growth is complete
• Closure times of epiphyseal plates are important indicators of animal age.
• Bone width increases due to growth at the subperiosteal membrane

Function of the Skeleton (8)

• Mechanical functions:
  • Protection: Skull (brain cage), vertebral canal (spinal cord), thoracic cage (heart, lungs)
  • Support/weight-bearing: Attachment points for soft tissues and organs.
  • Provides levers for skeletal motion (long and short bones in combination with muscles and articulation)
• Biological functions:
  • Mineral storage: Calcium, phosphorus, iron—important in understanding metabolic diseases and diagnostic imaging.
  • Hematopoiesis: Blood cell formation in bone marrow.

Descriptive Terms of the Skeletal System (9)

• Bony elevations (projections):
  • Head: Rounded (e.g., femoral head)
  • Condyle: More or less spherical (e.g., femoral condyles)
  • Trochlea: Pulley-like (e.g., femoral trochlea; patella)
  • Capitulum: Small head (referencing bony elevation)
• Non-articular projections:
  • Process: Elongated projection (e.g., spinal process).
  • Tuberosity: Relatively large rounded projection (e.g., lateral humeral tuberosity).
  • Tubercle: Small rounded elevation (e.g., psoas minor tubercle).
  • Crest: Elongated ridge (e.g., tibial crest).
  • Spine: Small projection like a thorn (e.g., scapular spine).
  • Neck: Constricted area below the head (e.g., humeral neck).
    • Line: Very low elevation demarcating an area (e.g., popliteal line).
  • Styloid: Thick pin-like projection (e.g., styloid process of ulna).
  • Hamulus: Curved, hook-like process (e.g., hamulus of pterygoid bone).
  • Epicondyle: Non-articular projection near a condyle (e.g., femoral epicondyles).
  • Trochanter: Large tuberosity—usually with square margins (associated with running).
  • Cornu (coronoid): Shaped like a deer's horn (e.g., mandibular coronoid process).
  • Ridge: Linear elevation with a sharp border
  • Border: Separates two surfaces

Descriptive Terms of the Skeletal System (II)

• Bony depressions (cavities):
  • Glenoid cavity: Shallow, articular concavity (e.g., scapular glenoid cavity)
  • Cotyloid: Deep, articular concavity (e.g., acetabulum)
  • Notch: Articular indentation (e.g., semilunar notch of ulna)
• Non-articular depressions:
  • Fossa: Large, non-articular depression (e.g., atlantal fossa)
  • Fovea: Small, non-articular depression (e.g., femoral fovea capitis)
  • Foramen: Perforation in bone, allowing passage of vessels and nerves (e.g., foramen magnum)
  • Fissure: Elongated deficiency like a cleft (e.g., palatine fissure)
  • Canal: Passage with two openings (e.g., vertebral canal)
  • Hiatus: Narrow passage with a hidden opening
  • Meatus: Shallow elongated passageway
  • Sulcus/groove: Linear depression with edges
  • Sinus: Air cavity lined with a mucous membrane.

Blood Supply of the Bone

• Periosteal arteries ramify in the periosteum and branch into the compact bone's Haversian canals.
• Other branches supply spongy bone at the ends of long bones
• Nutrient/medullary artery penetrates compact bone, ramifies through marrow, and anastomoses with periosteal branches
• Epiphyseal arteries supply the epiphyses
• Metaphysial arteries supply the metaphyses

Nerves of the Bone (5)

• Bones are provided with sensory nerve endings (e.g., Vater-Pacini corpuscles) situated in the periosteum.

Test your knowledge of animal skeletal systems with this quiz. Explore topics such as bone classification, types of skeletal structures, and functions related to growth and mobility. Ideal for students learning about animal anatomy and physiology.