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Questions and Answers
What is the primary bone that forms the arm?
What is the primary bone that forms the arm?
The radius is the medial bone in the anatomical position.
The radius is the medial bone in the anatomical position.
False
How many phalanges are there in each hand?
How many phalanges are there in each hand?
14
The _________ is the lateral bone in the anatomical position.
The _________ is the lateral bone in the anatomical position.
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Match the following bones with their characteristics:
Match the following bones with their characteristics:
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Which structure is found in compact bone and functions as a unit containing the central canal and matrix rings?
Which structure is found in compact bone and functions as a unit containing the central canal and matrix rings?
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Canaliculi are large canals that carry blood vessels and nerves through bone.
Canaliculi are large canals that carry blood vessels and nerves through bone.
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What are the small, needlelike pieces of bone found in spongy bone called?
What are the small, needlelike pieces of bone found in spongy bone called?
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The concentric circles of lacunae situated around the central canal are known as _____ .
The concentric circles of lacunae situated around the central canal are known as _____ .
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Match the following structures with their functions in bone:
Match the following structures with their functions in bone:
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What is the primary characteristic of synovial joints?
What is the primary characteristic of synovial joints?
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Bursae are considered a part of the joint structure.
Bursae are considered a part of the joint structure.
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Name one type of synovial joint.
Name one type of synovial joint.
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A _____ joint allows for the most movement and has a spherical shape.
A _____ joint allows for the most movement and has a spherical shape.
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Match the types of joints with their mobility:
Match the types of joints with their mobility:
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Which of the following is NOT a type of synovial joint?
Which of the following is NOT a type of synovial joint?
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Tendon sheaths are simply elongated bursae.
Tendon sheaths are simply elongated bursae.
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Which type of cartilage is known for its ability to absorb compressive shock?
Which type of cartilage is known for its ability to absorb compressive shock?
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Sutures are types of joints that allow significant movement.
Sutures are types of joints that allow significant movement.
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Name the joint type that allows slight movement and can be found in the pubic symphysis.
Name the joint type that allows slight movement and can be found in the pubic symphysis.
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Synovial joints have a joint ______ that contains synovial fluid.
Synovial joints have a joint ______ that contains synovial fluid.
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What type of joint is formed where the teeth meet the facial bones?
What type of joint is formed where the teeth meet the facial bones?
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The articular capsule is one of the four distinguishing features of synovial joints.
The articular capsule is one of the four distinguishing features of synovial joints.
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List one of the types of fibrous joints.
List one of the types of fibrous joints.
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Match the joint types with their descriptions:
Match the joint types with their descriptions:
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Study Notes
Essentials of Human Anatomy & Physiology - Chapter 5: The Skeletal System
- The skeletal system is comprised of bones, joints, cartilages, and ligaments
- The skeleton is divided into two subdivisions: axial and appendicular
- The axial skeleton forms the longitudinal axis of the body and includes the skull, vertebral column, and bony thorax.
- The appendicular skeleton is composed of the limbs (appendages), pectoral girdle, and pelvic girdle
Functions of the Bones
- Support the body
- Protect soft organs (skull and vertebrae protect brain and spinal cord, rib cage protects thoracic cavity organs)
- Allow movement via attached muscles
- Store minerals and fats (calcium and phosphorus, fat in the internal marrow cavity)
- Blood cell formation (hematopoiesis)
Classification of Bones
- The adult skeleton has 206 bones
- Two basic types of osseous tissue: compact bone and spongy bone
- Compact bone is dense, smooth, and homogeneous
- Spongy bone has small needlelike pieces of bone with many open spaces
- Bones are classified by shape into four groups: long, flat, short, and irregular
- Long bones are typically longer than they are wide, with a shaft and enlarged ends. Examples include the femur and humerus.
- Flat bones are thin, flattened, and usually curved, with two thin layers of compact bone sandwiching a layer of spongy bone. Examples include most bones of the skull, ribs, and sternum.
- Short bones are generally cube-shaped, containing mostly spongy bone with an outer layer of compact bone. Examples include carpals (wrist bones) and tarsals (ankle bones). Sesamoid bones, like the patella, are a type of short bone.
- Irregular bones have irregular shapes and don't fit into the other categories. Examples include vertebrae and hip bones.
Structure of Bone
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Long Bone Anatomy:
- Diaphysis (shaft): Composed of compact bone, makes up most of the bone’s length.
- Periosteum: Fibrous connective tissue membrane that covers the outside of the diaphysis; Perforating (Sharpey's) fibers secure the periosteum to the underlying bone.
- Epiphysis (ends): Composed mostly of spongy bone, enclosed by a thin layer of compact bone; Articular cartilage covers the external surface of the epiphyses and decreases friction at joint surfaces.
- Epiphyseal line: Remnant of the epiphyseal plate, seen in adult bones.
- Epiphyseal plate: Flat plate of hyaline cartilage that causes lengthwise growth of a long bone in young, growing bone.
- Medullary cavity: Cavity inside the shaft; Contains yellow marrow (mostly fat) in adults, and red marrow for blood cell formation until age 6 or 7.
- Endosteum: Lines the inner surface of the shaft, made of connective tissue.
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Bone Markings:
- Sites of attachments for muscles, tendons, and ligaments
- Passages for nerves and blood vessels
- Projections (processes) and depressions (cavities)
- Projections generally begin with "T" (e.g., tuberosity, trochanter).
- Depressions/cavities generally begin with "F" (e.g., fossa).
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Microscopic Anatomy of Spongy Bone:
- Composed of small, needlelike pieces of bone called trabeculae
- Open spaces are filled by marrow, blood vessels, and nerves.
-
Microscopic Anatomy of Compact Bone:
- Osteocytes: Mature bone cells situated in the bone matrix.
- Lacunae: Cavities in the bone matrix that house osteocytes.
- Lamellae: Concentric circles of lacunae situated around the central (Haversian) canal.
- Central (Haversian) canal: Opening in an osteon containing blood vessels and nerves.
- Canalculi: Tiny canals that radiate from the central canal to lacunae, forming a transport system connecting all bone cells to a nutrient supply.
- Bone is relatively lightweight and resists tension and other forces; organic parts (collagen fibers) provide flexibility with great tensile strength; calcium salts make bone hard and resistant to compression.
Bone Formation, Growth, and Remodeling
- Ossification: The process of bone formation that occurs on hyaline cartilage or fibrous membranes.
- Two major phases in long bone ossification:
- In embryos, osteoblasts cover a hyaline cartilage model with bone matrix.
- In fetuses, the cartilage is replaced by bone, creating a medullary cavity.
- Appositional growth: Bones grow in width by osteoblasts in the periosteum adding bone matrix on the outside and osteoclasts in the endosteum removing bone from the inner surface.
- Bone remodeling throughout life in response to two factors: calcium ion levels in the blood and the pull of gravity and muscles acting on the skeleton.
- Parathyroid hormone (PTH): Released when calcium levels are low; Activates osteoclasts (bone-destroying cells), which break down bone and release calcium ions into the blood.
- Hypercalcemia (high blood calcium): Prompts calcium storage in bones by osteoblasts.
Bone Fractures
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Fracture: a break in a bone
- Types: closed (simple) and open (compound)
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Treatment: reduction (manually coaxed into place or secured with pins/wires), immobilization.
-
Healing time: 6–8 weeks
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Repair involves four major events: hematoma formation, fibrocartilage callus formation, bony callus formation and bone remodeling.
Axial Skeleton
- Forms the longitudinal axis of the body and includes the skull, vertebral column, and bony thorax.
Skull
- Two sets of bones (cranial and facial) form the skull.
- Cranial bones enclose the brain, hold the eyes in anterior position (allow facial muscles to express feelings).
- Bones joined by immovable joints (sutures) except for mandible.
- 8 cranial bones: Frontal, Occipital, Ethmoid, Sphenoid, Parietal (pair), Temporal (pair)
- 14 facial bones: Maxillae(pair), Palatine(pair), Lacrimal(pair), Zygomatic(pair), Nasal(pair), Vomer, Inferior nasal conchae(pair), Mandible.
- Paranasal sinuses are hollow portions of bones surrounding the nasal cavity that lighten the skull and amplify sounds.
- Hyoid bone is a U-shaped bone that is closely related to mandibular and temporal bones; it's the only bone that doesn't articulate with another bone, as it serves as a movable base for the tongue; important for swallowing and speech.
Vertebral Column
- Vertebral column provides axial support; extends from the skull to the pelvis.
- 26 vertebrae separated by intervertebral discs.
- 7 Cervical vertebrae
- 12 Thoracic vertebrae
- 5 Lumbar vertebrae
- Sacrum (5 fused vertebrae)
- Coccyx (3-5 fused vertebrae)
- Primary and secondary curvatures of the vertebral column.
- Common features of vertebrae: Body (centrum), vertebral arch, pedicle, lamina, vertebral foramen, transverse processes, spinous process, superior and inferior articular processes.
Thoracic Cage
- Bony thorax (or thoracic cage) protects thoracic cavity organs
- Consists of three parts:
- Sternum
- Ribs (true, false, floating)
- Thoracic vertebrae
Appendicular Skeleton
- Composed of 126 bones, divided into limbs (appendages), pectoral girdle, and pelvic girdle.
Bones of the Pectoral Girdle
- Consist of two bones: Clavicle and Scapula.
- Light, poorly reinforced structure, but allows for exceptional flexibility of the upper limb.
Bones of the Upper Limbs
- Humerus (arm): head articulates with glenoid cavity of the scapula; distal end articulates with the bones of the forearm.
- Radius and ulna (forearm).
- Carpals (wrist), Metacarpals (palm), Phalanges (fingers and thumb)
Bones of the Pelvic Girdle
- Pelvic girdle and pelvis are made up of the Ilium, Ischium, and Pubis fused together.
- Protects several organs (reproductive, urinary bladder, part of large intestine).
- Female anatomy has a wider and proportionally shallower pelvic opening than male anatomy.
Bones of the Lower Limbs
- Femur (thigh): Head articulates with the acetabulum of the coxal bone; distal end articulates with the tibia.
- Tibia and fibula (lower leg).
- Tarsals (ankle), metatarsals (foot sole), phalanges (toes).
- Arched foot structure for support and balance.
Joints
- Joints are articulations where two or more bones meet.
- Functions: hold bones together securely, allow for mobility.
- Classification (two types):
- Functionally: Synarthroses (immovable), Amphiarthroses (slightly movable), Diarthroses (freely movable).
- Structurally: Fibrous (generally immovable; sutures, syndesmoses, gomphoses), Cartilaginous (immovable or slightly movable; synchondrosis, symphysis), Synovial (freely movable: plane, hinge, pivot, condylar, saddle, ball-and-socket).
- Bursae and tendon sheaths are flattened fibrous sacs or elongated bursae that wrap around tendons; lined with synovial membranes; filled with synovial fluid, not part of the joint.
Developmental Aspects of the Skeleton
- Birth to adulthood: bones develop from hyaline cartilage models or fibrous membranes by ossification; most cartilage converted to bone, except for articular cartilage and epiphyseal plates.
- Fontanels: fibrous membranes connecting cranial bones in the fetal skull, act as "soft spots" that allow brain growth. Usually ossify by two year age.
- Growth after birth is related to the brain; the facial skeleton enlarges (due to tooth development and respiratory passages).
- Size of cranium in relation to body; body proportions change during puberty (pelvis broadens for females). Epiphyseal plates completely ossify by the end of adolescence.
- Osteoporosis (age-related disease): bone-thinning; vertebral collapse can occur
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