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How many bones make up the adult human skeleton?
The appendicular skeleton consists of 80 bones.
False
What type of bone is primarily found in short bones?
spongy
The skeletal system is part of the __________ system, which underscores their interdependence.
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Match the type of bones with their descriptions:
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What is the function of the skull?
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The mandible is the only immovable bone of the skull.
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What is the keystone of the cranial floor?
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The bony structure forming the forehead is called the __________.
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Match the bones with their locations:
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Which of the following bones contains the crista galli?
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The external auditory meatus directs sound waves toward the cochlea.
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What are the auditory ossicles called?
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The __________ forms the inferior portion of the nasal septum.
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Which bones form the zygomatic arch?
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There are 32 bones in the adult human skull.
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What is the primary function of fontanels in infants?
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The __________ provides passage for the spinal cord to connect with the brain.
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Match the types of bones with their corresponding locations or functions:
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What forms the neck region of the vertebral column?
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The thoracic vertebrae have no transverse processes.
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What is the main purpose of the intervertebral discs?
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The first cervical vertebra is called the _________.
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Match the vertebra type with their characteristics:
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What is the purpose of the curves of the spine?
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The coccyx consists of three fused vertebrae.
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What is the term for the abnormal lateral bending of the vertebral column?
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The person becomes tallest right after waking because the intervertebral discs ________ during the day.
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Match the rib types to their descriptions:
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What part of the sternum is the most superior?
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The lumbar vertebrae are identified by the letter L followed by numbers one through five.
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What condition may be reduced by taking folic acid during pregnancy?
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The ribcage is comprised of the __________ and __________ ribs.
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Which cervical vertebra permits rotation of the head?
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The vertebral canal ends at the sacral canal.
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Study Notes
The Human Skeleton
- The adult human skeleton is composed of 206 bones.
- It is divided into two main groups: the axial skeleton (80 bones) and the appendicular skeleton (126 bones).
- The axial skeleton includes the bones that run from the head to the bottom of the vertebral column.
- The appendicular skeleton includes the bones of the limbs and the girdles that attach the limbs to the axial skeleton.
- The muscular and skeletal systems are often considered together as the musculoskeletal system.
- The skeleton is composed of five main types of bones: long, short, flat, sesamoid, and irregular.
Long Bones
- Longer than they are wide and curved to absorb shock.
- Spongy bone tissue is found in the epiphyses (ends of the bone).
- Compact bone tissue is found in the diaphysis (shaft of the bone).
- Example: Femur
Short Bones
- Nearly as long as they are wide.
- Mostly composed of spongy bone tissue surrounded by a thin layer of compact bone.
- Example: Carpals of the wrist
Flat Bones
- Thin plates of compact bone with spongy bone interiors.
- Examples: Skull bones, ribs
Sesamoid Bones
- Small, thin bones that develop in areas of high mechanical stress.
- They help protect tendons by modulating tension during movement.
- Example: Patella (kneecap)
Irregular Bones
- May be irregularly shaped or distributed.
- Examples: Vertebrae
Bone Markings
- Depressions and openings provide passage for blood vessels and nerves.
- Processes, projections, or outgrowths serve as attachment points for ligaments and tendons.
The Skull
- Functions of the skull include:
- Protecting the brain
- Serving as a point of attachment for facial muscles
- Forming portions of the orbits, nasal cavity, and oral cavity
- Housing the auditory ossicles, which are involved in hearing.
Cranial Bones
- There are 22 cranial bones in the skull (some are paired).
- Bones of the cranial cavity:
- Frontal
- Parietal (left and right)
- Temporal (left and right)
- Sphenoid
- Ethmoid
- Occipital
- Frontal Bone: Forms the forehead and contains the supraorbital foramen, which allows passage for the supraorbital artery and nerve.
- Ethmoid Bone: Forms the medial portion of the orbits, the anterior portion of the cranial floor, and contains the crista galli, a triangular process that serves as an attachment point for the membrane separating the two halves of the brain. Also contains the cribriform plate with olfactory foramina, providing passage for sensory structures involved in smell.
- Sphenoid Bone: Known as the "keystone" of the cranial floor and contains the optic foramen, which allows passage of the ophthalmic artery and optic nerve.
- Temporal Bones: Form the lateral and inferior portions of the cranium, contribute to the zygomatic arch, contain the mandibular fossa, which houses the mandibular condyle, and contain the styloid process, mastoid process, and external auditory meatus.
- Auditory Ossicles: Malleus, incus, and stapes, which transmit sound vibrations from the eardrum to the inner ear.
- Occipital Bone: Forms the posterior and inferior portion of the skull, contains the occipital condyles, which articulate with the atlas, and the foramen magnum, which provides passage for the spinal cord.
- Parietal Bones: Form the superior and lateral portions of the skull.
Facial Bones
- There are 14 facial bones in the skull.
- Mandible: The largest, strongest, and only movable bone of the skull. It forms the lower jaw and its condyle process articulates with the temporal bone's mandibular fossa.
- Maxillae: Form the upper jaw, are fused in adults, contain the palatine process, which forms the hard palate, and the infraorbital foramen, which allows passage for blood vessels and the fifth cranial nerve.
- Palatine Bones: L-shaped bones that complete the posterior portion of the hard palate.
- Zygomatic Bones: Form the anterior portion of the cheekbones and contribute to the orbits (eye sockets).
- Vomer: Forms the inferior portion of the nasal septum.
- Inferior Nasal Conchae: Curved bones that form the lateral walls of the nasal cavity, swirling air around the nasal passages to trap airborne invaders.
- Nasal Bones: Form the bridge of the nose.
- Lacrimal Bones: Smallest of the facial bones, located near the tear ducts.
Special Features of the Skull
- Orbits: Eye sockets formed by seven bones: frontal, ethmoid, sphenoid, lacrimal, maxilla, zygomatic, and palatine.
- Sutures: Fibrous joints between cranial bones that allow for skull growth during infancy. These soft spots called fontanels allow for brain growth and facilitate passage of the newborn's head through the birth canal during labor.
- Coronal Sutures: Connects the frontal and parietal bones.
- Sagittal Sutures: Connects the parietal bones superiorly.
- Lambdoid Sutures: Connects the parietal and occipital bones.
- Squamous Sutures: Connects the parietal and temporal bones.
- Zygomatic Arch: Prominent bony portion running laterally and posteriorly from the zygomatic bone, formed by the zygomatic and temporal bones.
- Paranasal Sinuses: Air-filled cavities lined with mucous membranes that lighten the skull and trap invaders.
- Hyoid Bone: A unique bone that does not articulate with any other bone. It is suspended by ligaments and muscles, supporting the tongue and its muscles.
The Vertebral Column
- Functions:
- Supports and moves the skull
- Protects the spinal cord
- Provides attachment points for back and abdominal muscles
- Contains intervertebral discs for cushioning
- Divided into regions: cervical, thoracic, lumbar, sacral, and coccygeal.
- Normal curves help with shock absorption.
- Intervertebral discs: Fibrocartilaginous structures between vertebrae that compress throughout the day, causing us to be tallest right after waking.
- Vertebral Anatomy:
- Body: Bears weight and contains nutrient foramina.
- Vertebral foramen: Encloses the spinal cord.
- Superior and inferior articular processes: Articulate with adjacent vertebrae.
- Facets: Surfaces where bones meet.
Cervical Vertebrae
- Superiormost vertebrae, forming the neck.
- Seven cervical vertebrae (C1-C7).
- C1 (Atlas): Lacks a body and spinous process, has a large vertebral foramen that accommodates the dens, and permits head nodding movements.
- C2 (Axis): Features the dens (odontoid process), which projects superiorly and passes through the atlas' vertebral foramen, allowing head rotation.
- Special properties:
- Bifid Spinous Processes: Two-pronged projections.
- Transverse Foramen: Transmits the vertebral artery which supplies the head.
Thoracic Vertebrae
- 12 Thoracic vertebrae (T1-T12).
- Have large transverse processes for articulation with ribs.
- Demifacets: Surfaces on T1-T12 that connect the head of a rib with two vertebrae.
-
Rib Anatomy:
- Head: Articulates with demifacets on two vertebral bodies.
- Neck: Narrowed region adjacent to the head.
- Tubercle: Posterior and lateral projection that articulates with facets on the transverse processes of thoracic vertebrae.
Lumbar Vertebrae
- 5 Lumbar vertebrae (L1-L5).
- Short and thick spinous processes, providing attachment points for back muscles.
Sacrum
- 5 fused vertebrae.
- Articulates with the pelvic girdle at the sacroiliac joints.
- The vertebral canal becomes the sacral canal, ending at the sacral hiatus (inferior opening).
Coccyx
- Tailbone made up of 4 fused coccygeal vertebrae (Co1-Co4).
Thoracic Cage
- Forms the ribcage and breastbone (sternum).
-
Sternum
- Manubrium: Superior portion.
- Body: Long, intermediate portion.
- Xiphoid Process: Tiny, inferior portion.
- Suprasternal Notch: Medial depression between clavicular notches.
- Clavicular Notches: Where the clavicles (collarbones) articulate with the sternum.
Ribs
- True Ribs: First seven ribs (superior to inferior); articulate with the thoracic vertebrae AND the sternum.
- False Ribs: Ribs 8-10; articulate with the thoracic vertebrae BUT NOT the sternum; instead, they attach to the costal cartilages of the 7th rib.
- Floating Ribs: Ribs 11-12; do not articulate with any bones anteriorly.
Disorders of the Axial Skeleton
-
Scoliosis: Lateral bending of the vertebral column.
- Signs: Uneven shoulders, uneven waist.
- Symptoms: Chronic back pain, arthritis.
- Severe cases can lead to difficulty breathing.
- Treatment: Bracing, physical therapy, surgery.
-
Spina Bifida: Incomplete closing of the vertebral column during fetal development.
- Spinal cord may protrude (meningocele).
- Folic acid supplementation during pregnancy helps reduce the risk of spina bifida and other neural tube defects
- Treatment: Physical therapy, surgery.
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Description
This quiz covers key aspects of the human skeleton, including the number of bones and their classification into axial and appendicular groups. It also explores the different types of bones such as long, short, and their characteristics. Test your knowledge of the structure and function of the skeleton!
