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Questions and Answers
How many bones are in the adult human skeleton?
How many bones are in the adult human skeleton?
The appendicular skeleton includes the bones that support the head and neck.
The appendicular skeleton includes the bones that support the head and neck.
False
What type of bone tissue predominantly makes up short bones?
What type of bone tissue predominantly makes up short bones?
spongy
The axial skeleton contains 80 bones and is mainly composed of bones that run from the head to the bottom of the _column.
The axial skeleton contains 80 bones and is mainly composed of bones that run from the head to the bottom of the _column.
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Match the following types of bones with their descriptions:
Match the following types of bones with their descriptions:
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Which of the following is NOT a sign of unequal leg length?
Which of the following is NOT a sign of unequal leg length?
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Folic acid supplementation during pregnancy increases the risk of spina bifida.
Folic acid supplementation during pregnancy increases the risk of spina bifida.
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What condition is characterized by incomplete closing of the vertebral column during fetal development?
What condition is characterized by incomplete closing of the vertebral column during fetal development?
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Treatment for unequal leg length might include a _______ or physical therapy.
Treatment for unequal leg length might include a _______ or physical therapy.
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Match the following components of the axial skeleton with their descriptions:
Match the following components of the axial skeleton with their descriptions:
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Which of the following accurately describes the hyoid bone?
Which of the following accurately describes the hyoid bone?
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The sacrum is composed of five non-fused vertebrae.
The sacrum is composed of five non-fused vertebrae.
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What are the first seven ribs called?
What are the first seven ribs called?
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The vertebral column protects the _____ cord.
The vertebral column protects the _____ cord.
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Match the vertebral regions with their number of vertebrae:
Match the vertebral regions with their number of vertebrae:
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What are the functions of the intervertebral discs?
What are the functions of the intervertebral discs?
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C1 is known as the axis.
C1 is known as the axis.
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What is the term for the abnormal lateral bending of the vertebral column?
What is the term for the abnormal lateral bending of the vertebral column?
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The _____ process is the tiny inferior bone of the sternum.
The _____ process is the tiny inferior bone of the sternum.
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Which vertebrae have bifid spinous processes?
Which vertebrae have bifid spinous processes?
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The thoracic cage consists of the sternum and the floating ribs.
The thoracic cage consists of the sternum and the floating ribs.
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Name the two specialized cervical vertebrae.
Name the two specialized cervical vertebrae.
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True ribs articulate with the thoracic vertebrae and the _____ bone.
True ribs articulate with the thoracic vertebrae and the _____ bone.
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What are demifacets?
What are demifacets?
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What function does the skull NOT perform?
What function does the skull NOT perform?
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The mandible is the only moveable bone of the human skull.
The mandible is the only moveable bone of the human skull.
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Name one of the bones that form the cranial cavity.
Name one of the bones that form the cranial cavity.
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The _____ condyles _____ form joints with the first cervical vertebra.
The _____ condyles _____ form joints with the first cervical vertebra.
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Which bone serves as the 'keystone' of the cranial floor?
Which bone serves as the 'keystone' of the cranial floor?
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The maxillae form the lower jaw.
The maxillae form the lower jaw.
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What is the role of the cribriform plate?
What is the role of the cribriform plate?
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The _____ nasal conchae _____ help to swirl air around nasal passages.
The _____ nasal conchae _____ help to swirl air around nasal passages.
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Which auditory ossicle is known as the 'stirrup'?
Which auditory ossicle is known as the 'stirrup'?
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Match the following cranial bones with their characteristics:
Match the following cranial bones with their characteristics:
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The temporal bones are located at the top of the skull.
The temporal bones are located at the top of the skull.
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What forms the lateral walls of the nasal cavity?
What forms the lateral walls of the nasal cavity?
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The _____ ethmoid _____ bone is found at the anterior cranial floor.
The _____ ethmoid _____ bone is found at the anterior cranial floor.
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Which of the following bones forms part of the zygomatic arch?
Which of the following bones forms part of the zygomatic arch?
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How many pairs of parietal bones are present in the skull?
How many pairs of parietal bones are present in the skull?
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Study Notes
The Human Skeleton
- The adult human skeleton is composed of 206 bones.
- The skeleton can be divided into two main groups: the axial skeleton (80 bones), which includes the bones that run from head to bottom of the vertebral column, and the appendicular skeleton (126 bones), which includes the bones of the limbs and the girdles that attach limbs to the axial skeleton.
- The skeleton is part of the musculoskeletal system, which is the muscular and skeletal system combined.
- The musculoskeletal system underscores the interdependence of the muscles and the skeleton, and the two work together to facilitate movement.
- The skeleton is composed of five main types of bones:
- Long bones: Longer than they are wide, curved to absorb shock evenly.
- Short bones: Nearly as long as they are wide, consist mostly of spongy bone tissue surrounded by a thin layer of compact bone.
- Flat bones: Thin plates of compact bone that contain spongy bone interiors.
- Sesamoid bones: Thin, small bones that develop in areas of high mechanical stress, protect tendons by modulating tension during movement.
- Irregular bones: Irregularly-shaped or distributed bones.
- Bones have surface markings that serve physiological functions:
- Depressions and openings: Provide passage for blood vessels and nerves (foramina, fossae, and meati).
- Processes, projections, or outgrowths: Attachment points for ligaments and tendons (condyles, facets, heads, crests, and processes).
- The human skull is composed of 22 bones and includes the cranial and facial bones.
- The cranial bones protect the brain, serve as a point of attachment for facial muscles, form portions of the orbits, nasal, and oral cavities, and include the auditory ossicles, which ensure you can sense auditory signals.
Cranial Bones
- Frontal bone: Forms the forehead at the anterior of the skull, the supraorbital foramen provides passage for the supraorbital artery and nerve.
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Ethmoid bone: Forms the medial portion of the orbits and the anterior portion of the cranial floor.
- The crista galli is a triangular process where the membrane that separates the two halves of the brain attaches.
- The cribriform plate contains the olfactory foramina, which provides passage for sensory structures required for smell.
- The perpendicular plate forms the superior part of the nasal septum.
- Sphenoid bone: The "keystone" of the cranial floor, contains the optic foramen that allows passage of the ophthalmic artery and the optic nerve.
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Temporal bones: Forms the lateral and inferior portions of the cranium.
- The zygomatic arch forms the lateral part of the "cheekbone."
- The mandibular fossa forms a cavity that accommodates the mandibular condyle.
- The styloid process is a point of attachment for neck and tongue muscles.
- The mastoid process is a point of attachment for neck muscles.
- The external auditory meatus forms the ear canal, directing sound waves towards the auditory ossicles.
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Auditory ossicles: Sound waves hit the tympanic membrane, which vibrates the auditory ossicles and vibrations are sensed by auditory sensory structures.
- Malleus (hammer)
- Incus (anvil)
- Stapes (stirrup)
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Occipital bone: Forms the posterior and inferior portion of the skull.
- The occipital condyles form joints with the first cervical vertebra (atlas) which forms the atlantooccipital joint.
- The foramen magnum provides passage for the spinal cord to connect with the brain.
- Parietal bones: Forms the superior and lateral portions of the skull.
Facial Bones
- 14 facial bones form the anterior portion of the skull:
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Mandible: Forms the lower jaw, largest, strongest bone of the skull, the only moveable bone of the skull.
- The condylar process articulates with the mandibular fossa of the temporal bone.
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Maxillae: Forms the upper jaw; two bones (left and right) that are fused in adults.
- The palatine process provides passage for the infraorbital blood vessels and nerves, and forms most the hard palate.
- Palatine bones: L-shaped bones that complete the posterior portion of the hard palate.
- Zygomatic bones: Form the anterior portion of the "cheekbones" and the inferior and lateral walls of the orbits.
- Vomer: Latin for ploughshare and forms the inferior portion of the nasal septum.
- Inferior nasal conchae: Form the lateral walls of the nasal cavity, the curled appearance helps to swirl air around the passages, increasing the chance of trapping airborne invaders.
- Nasal bones: Form the bridge of the nose.
- Lacrimal bones: The smallest of the facial bones, lie near the tear ducts.
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Mandible: Forms the lower jaw, largest, strongest bone of the skull, the only moveable bone of the skull.
Special Features of the Skull
- The orbits contain the eyes and are made of seven bones:
- Frontal bone
- Lacrimal bone
- Ethmoid bone
- Zygomatic bone
- Sphenoid bone
- Maxilla
- Palatine bone
- The sutures:
- Recall that the skeleton is incompletely ossified at birth and these "soft spots" are called fontanels.
- Mesenchymal tissue persists and becomes dense connective tissue.
- The function of fontanels is to allow babies' brains to grow and for the cranium to grow to accommodate the brain, allowing the newborn head to pass through the birth canal during labor.
- Recall that the skeleton is incompletely ossified at birth and these "soft spots" are called fontanels.
- The coronal and sagittal cranial sutures:
- The coronal suture connects the frontal and parietal bones.
- The sagittal suture connects the parietal bones superiorly.
- The lambdoid suture articulates the parietal bone and the occipital bone.
- The squamous suture articulates the parietal and temporal bone.
- The cheekbones are actually two bones: The zygomatic bone and the temporal bone, which together form the zygomatic arch.
- The paranasal sinuses are formed by the facial bones:
- The sinuses are cavities lined with mucous membranes that help to trap invaders as air is inhaled.
- They make the skull lighter.
Hyoid Bone
- This special bone does not articulate with any other bones.
- It "floats" on tendons and ligaments.
- The muscles of the tongue attach to the hyoid bone.
- The hyoid bone is not the Adam's apple in males (that is composed of thyroid cartilage).
The Vertebral Column
- Functions: Supports and moves the skull, protects the spinal cord, provides points of attachment for the muscles of the back and abdomen, and contains intervertebral discs that cushion vertebrae from shock.
- Divied into subregions and curved to improve shock absorption.
- The normal curves of the spine (the cervical and lumbar curves) are acquired as a result of holding our heads up and learning to walk.
- Intervertebral discs:
- Cushioned discs of fibrocartilage that lie between vertebrae.
- They compress throughout the day as they dehydrate, which is why we are tallest immediately after waking.
Vertebral Anatomy
- Body: Bears weight and contains nutrient foramina.
- Vertebral foramen: Provides passage for the spinal cord.
- Superior articular processes: Articulate (form joints with) the inferior articular processes of the vertebrae above them.
- Facets: The surfaces on which bones connect to one another at joints.
Cervical Vertebrae
- The most superior of the vertebrae and form the neck.
- Numbered C1-C7.
- C1 (atlas) and C2 (axis) have special names.
- C1: Has no body and no spinous process, has a distinct anterior arch, and has a large vertebral foramen that accommodates the dens of the axis (C2).
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C2: The dens is a large superior and anterior projection that passes through the vertebral foramen of the atlas.
- The dens and the atlas form the atlantoaxial joint, which permits turning of the head left and right.
- The spinous processes are bifid (two heads).
- The transverse processes have the transverse foramen that provides passage for the vertebral artery, the major posterior blood vessel that services the head.
Thoracic Vertebrae
- Numbered T1-T12.
- Have large transverse processes for articulation with the ribs.
- Demifacets: Unique to thoracic vertebrae, the surfaces on which the head of one rib connects with two vertebrae.
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Rib anatomy:
- The head of the rib articulates with demifacets on two vertebral bodies.
- The narrowed region adjacent to the head is called the neck.
- The tubercle is a posterior and lateral projection that articulates with facets on the transverse processes of thoracic vertebrae.
Lumbar Vertebrae
- Numbered L1-L5.
- Short and thick spinous processes that are points of attachment for the muscles of the back.
Sacrum & Coccyx
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Sacrum: 5 fused vertebrae that articulates with the pelvic girdle (hip bones) at the sacroiliac joints.
- The vertebral canal become the sacral canal at the sacral vertebrae and ends at the sacral hiatus (the inferior opening).
- Coccyx: The tailbone, four fused coccygeal vertebrae (Co1-Co4).
Thoracic Cage
- Forms the rib cage and breastbone.
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Sternum (breastbone): Medial bone to which the ribs attach.
- The manubrium is the most superior portion.
- The body is the long intermediate portion.
- The xiphoid process is the tiny inferior bone.
- The suprasternal notch is a medial depression between the clavicular notches.
- The clavicular notches are the sites of articulation between the sternum and the clavicles (collarbones).
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Ribs:
- True ribs (1-7): Articulate with the thoracic vertebrae and the sternum.
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False ribs (8-10): Articulate with the thoracic vertebrae but not with the sternum.
- The ribs 8-10 articulate anteriorly with the costal cartilage of the 7th rib.
- Costal cartilage is made of hyaline cartilage.
- Floating ribs (11-12): Do not articulate with any bones anteriorly.
Disorders of the Axial Skeleton
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Scoliosis: Lateral bending of the vertebral column, often at the thoracic vertebrae.
- May be inherited or compensatory (in response to unequal leg length).
- Signs: Uneven shoulders and/or waist, difficulty breathing (in severe cases).
- Symptoms: Chronic back pain and arthritis
- Treatment: Brace, physical therapy, surgery
-
Spina bifida: Incomplete closing of the vertebral column during fetal development.
- The spinal cord may protrude, resulting in a meningocele.
- Folic acid supplementation during pregnancy decreases the risk of spina bifida and other neural tube defects.
- Treatment: Physical therapy, surgery.
Summary
- The axial skeleton includes the bones of the:
- Cranium
- Face
- Vertebral column
- Thoracic cage.
- These bones are a source of red bone marrow.
- These bones protect the internal organs, including the brain, the spinal cord, and the viscera of the thoracic cavity.
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Description
Explore the fascinating components of the adult human skeleton, which comprises 206 bones divided into the axial and appendicular groups. This quiz will also cover the five main types of bones and their roles within the musculoskeletal system. Test your knowledge about how these bones work together to facilitate movement.
