Human Anatomy: Skeletal System

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Questions and Answers

What is the typical state of the fontanelle by the end of the 1st year?

Partially closed

Completely closed (correct)

Still open

Not palpable but still open

What is the shape of the tympanic part of the temporal bone at birth?

Oval-shaped

C-shaped (correct)

Triangular

S-shaped

What is the state of the mastoid process at birth?

Fused with the temporal bone

Fully developed

Absent (correct)

Partially developed

How are the right and left halves of the mandible united at birth?

With fibrous tissue Signup and view all the answers

When do the two halves of the mandible fuse at the symphysis menti?

By the end of the 1st year Signup and view all the answers

What happens to the angle of the mandible after eruption of permanent teeth?

It assumes the adult shape Signup and view all the answers

What is the most anterior and shallowest of the three cranial fossae?

Anterior cranial fossa Signup and view all the answers

What forms the boundary between the anterior and middle cranial fossae?

Lesser wings of the sphenoid bone Signup and view all the answers

What is located at the midline of the floor of the anterior cranial fossa?

Crista galli of the ethmoid bone Signup and view all the answers

Which suture is seen on the internal surface of the cranial vault?

All of the above Signup and view all the answers

What is situated posterior to the anterior fossa and occupied by the temporal lobes of the brain?

Middle cranial fossa Signup and view all the answers

What forms the floor of the anterior cranial fossa?

Frontal bone Signup and view all the answers

What is the shape of the middle cranial fossa?

Butterfly shape Signup and view all the answers

What is seen on either side of the sagittal sulcus?

Granular pits Signup and view all the answers

Which of the following foramina is located on the medial wall of the petrous ridge in the posterior cranial fossa?

Internal acoustic meatus Signup and view all the answers

What is the function of the internal acoustic meatus?

Provides a passage for the nerve from the hearing and equilibrium organs of the inner ear, and the nerve that supplies the muscles of the face Signup and view all the answers

What is the location of the hypoglossal canal?

At the anterior-lateral margin of the foramen magnum Signup and view all the answers

Which of the following features is characteristic of the newborn skull?

A disproportionately large cranium relative to the face Signup and view all the answers

What is the shape of the anterior fontanelle?

Diamond shaped Signup and view all the answers

What is the location of the posterior fontanelle?

Between the two parietal bones in front and the occipital bone behind Signup and view all the answers

By what age is the anterior fontanelle closed?

18 months Signup and view all the answers

What is the characteristic of the bones of the skull in the newborn?

The bones are unilaminar and smooth Signup and view all the answers

Which part of the sphenoid bone forms the upward bony prominence that divides the middle cranial fossa at the midline?

Sella turcica Signup and view all the answers

Which opening in the middle cranial fossa provides a passage for the optic nerve into the orbit?

Optic canal Signup and view all the answers

Which nerve passes through the foramen rotundum?

A major sensory nerve that supplies the cheek, nose, and upper teeth Signup and view all the answers

Which opening in the middle cranial fossa provides passage for a major sensory nerve to the lateral head, cheek, chin, and lower teeth?

Foramen ovale Signup and view all the answers

What is the function of the foramen spinosum?

Entry point for an important artery that supplies the covering layers surrounding the brain Signup and view all the answers

What is the boundary of the posterior cranial fossa anteriorly?

Petrous ridges Signup and view all the answers

What is the function of the foramen magnum?

Passage for the spinal cord Signup and view all the answers

Which part of the brain is located in the posterior cranial fossa?

Cerebellum Signup and view all the answers

Study Notes

Internal Surface of Cranial Vault

The internal surface of the cranial vault shows the following features:
Coronal suture, sagittal suture, and lambdoid sutures
Frontal crest lies anteriorly in the median plane
Sagittal sulcus runs medially along the adjoining margins of parietal bones
Deep irregular pits for arachnoid granulations called granular pits are seen on either side of the sagittal sulcus
Vascular markings for branches of middle meningeal vessels are seen on either side

Internal Surface of Base of Skull

The floor of the cranial cavity is subdivided into three cranial fossae:
Anterior cranial fossa:
- The most anterior and the shallowest of the three cranial fossae
- Overlies the orbits and contains the frontal lobes of the brain
- Bounded anteriorly by the frontal bone, which also forms the majority of its floor
- The lesser wings of the sphenoid bone form the prominent ledge that marks the boundary between the anterior and middle cranial fossae
Middle cranial fossa:
- Deeper and situated posterior to the anterior fossa
- Occupied by the temporal lobes of the brain
- Extends from the lesser wings of the sphenoid bone anteriorly to the petrous ridges posteriorly
- The petrous ridges give the middle cranial fossa a butterfly shape, making it narrow at the midline and broad laterally
- Divided at the midline by the upward bony prominence of the Sella turcica
- Openings for the passage of blood vessels and cranial nerves:
  - Optic canal
  - Superior orbital fissure
  - Foramen rotundum
  - Foramen ovale
  - Foramen spinosum
Posterior cranial fossa:
- The most posterior and deepest portion of the cranial cavity
- Contains the cerebellum of the brain
- Bounded anteriorly by the petrous ridges, while the occipital bone forms the floor and posterior wall
- Divided at the midline by the large foramen magnum
- Openings for the passage of blood vessels and cranial nerves:
  - Internal acoustic meatus
  - Hypoglossal canal
  - Jugular foramen

Neonatal Skull

The newborn skull:
Has a disproportionately large cranium relative to the face
The bones of the skull are smooth and unilaminar
Most of the skull bones are ossified at birth, but the process is incomplete, and the bones are mobile on each other
The bones of the vault are not closely joined at sutures, as in the adult, but are separated by unossified membranous intervals called fontanelles
Clinically, the anterior and posterior fontanelles are most important and are easily examined in the midline of the vault
The anterior fontanelle is diamond-shaped and lies between the two halves of the frontal bone in front and the two parietal bones behind
The fibrous membrane forming the floor of the anterior fontanelle is replaced by bone and is closed by 18 months of age
The posterior fontanelle is triangular and lies between the two parietal bones in front and the occipital bone behind
By the end of the 1st year, the fontanelle is usually closed and can no longer be palpated
Other features of the newborn skull:
The tympanic part of the temporal bone is a C-shaped ring at birth
The external auditory meatus is almost entirely cartilaginous in the newborn
The mastoid process is not present at birth and develops later in response to the pull of the sternocleidomastoid muscle
The mandible has right and left halves at birth, united in the midline with fibrous tissue
The two halves fuse at the symphysis menti by the end of the 1st year
The angle of the mandible at birth is obtuse, and the head of the condyle being placed level with the upper margin of the body of the mandible

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Description

Learn about the internal surface of the cranial vault, including sutures, crests, sulcus, and granular pits. A key concept in human anatomy, particularly the skeletal system.

Human Anatomy: Skeletal System - Cranial Vault

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