Microscopic Structure and Ossification of Bone

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Questions and Answers

Which of the following is NOT a type of cartilage?

Fibrocartilage

Hyaline

Fibroergic (correct)

Elastic

What do canaliculi primarily provide in the bone structure?

Storage for marrow and fat

Communication and transport for nutrients (correct)

Protection against fracture

Support for blood vessel attachment

What happens to the epiphyseal plate after adolescence?

It continues to grow longer indefinitely

It thickens to support increased growth

It becomes flexible to adapt to movement

It is replaced by a calcified bony epiphyseal line (correct)

Where are osteocytes found within the bone structure?

In the lacunae Signup and view all the answers

Which type of cartilage connects the ribs to the sternum?

Hyaline cartilage Signup and view all the answers

What is the primary role of the periosteum during bone formation?

To replace the perichondrium Signup and view all the answers

What structure is also known as the Haversian system?

Osteon Signup and view all the answers

Which type of cartilage is found in the intervertebral discs?

Fibrocartilage Signup and view all the answers

What structures pass through the Foramen Lacerum?

Internal carotid artery and small nerves Signup and view all the answers

Which structure forms the posterior portion of the cranium?

Occipital bone Signup and view all the answers

Where do the Occipital Condyles articulate?

With the C1 vertebra (Atlas) Signup and view all the answers

Which cranial nerves pass through the Superior Orbital Fissures?

III, IV, V, and VI Signup and view all the answers

What is the primary role of the Superior and Middle Nasal Conchae?

Warm and humidify incoming air Signup and view all the answers

What is the function of the Crista Galli in the Ethmoid bone?

Anchors the dura mater of the brain Signup and view all the answers

Which statement about the Mandible is true?

It articulates with the temporal bone via the only freely moving joint in the skull. Signup and view all the answers

Which of the following bones is considered part of the facial bones?

Vomer Signup and view all the answers

Which of the following is NOT a component of the Axial Skeleton?

Pelvic Girdle Signup and view all the answers

What is a major effect of osteoporosis on the bones?

Gradual loss of bone mass Signup and view all the answers

What is the purpose of the supraorbital foramens in the frontal bone?

To permit blood vessels and nerves to pass Signup and view all the answers

Which cranial bones articulate at the Squamous Suture?

Temporal and Parietal Signup and view all the answers

What is the function of the Mandibular fossa?

Articulation site with the mandible Signup and view all the answers

Which structure is located in the temporal bones and is associated with hearing?

External Acoustic Meatus Signup and view all the answers

Mastoiditis primarily affects which part of the temporal bone?

Mastoid process Signup and view all the answers

What is the significance of the Stylomastoid foramen?

Opening for cranial nerve VII Signup and view all the answers

Study Notes

Microscopic Structure of the Bone

Marrow is found in the spaces of spongy bone, particularly in the epiphyses.
A central Haversian canal runs parallel to the long axis of the bone, carrying blood vessels, nerves, and lymph vessels.
Osteocytes (mature bone cells) reside in lacunae, chambers arranged in concentric circles (lamellae) around the central canal.
An osteon, or Haversian system, encompasses the central canal and all its concentric lamellae.
Canaliculi, tiny canals radiating from the central canal, serve as a communication and transport network for nutrients.
Volkmann's canals, perpendicular to the shaft, connect the central cavities and extend from the periosteum to the bone marrow cavity.

Ossification of Bone

Endochondral ossification utilizes hyaline cartilage as a template for bone formation.
Bone formation initiates from the primary ossification center, following these steps:
- Periosteum replaces perichondrium.
- Osteoblasts secrete bone around the hyaline cartilage model.
- Cartilage in the shaft center calcifies and hollows, forming a cavity.
- A periosteal bud (containing osteoblasts, osteoclasts, blood vessels, red marrow, and nerves) invades the cavity, establishing a medullary cavity on either side of the primary ossification center.
- The medullary cavity elongates and expands during bone growth.
- Following adolescence, the epiphyseal plate of ossifying cartilage is replaced by a calcified bony epiphyseal line.

Cartilage

Cartilage primarily consists of water, along with varying amounts of elastic, reticular, or collagen fibers.
Cartilage is enclosed by an outer covering called perichondrium, which plays a role in cartilage growth and repair.
Cartilage lacks nervous enervation and is relatively avascular.
Three types of cartilage exist: elastic, hyaline, and fibrocartilage.

Cartilages of the Skeleton

Articular cartilage, hyaline in nature, is found at the epiphyses of long bones.
Costal cartilage, also hyaline, connects the ribs to the sternum (breastbone).
Laryngeal cartilage, another hyaline type, constructs the voice box in the larynx.
Tracheal and bronchial cartilages, composed of hyaline cartilage, reinforce the passageways of the respiratory system.
Nasal cartilage, hyaline, supports the external nose.
Intervertebral discs cartilage, composed of fibrocartilage, separates and cushions the bones of the spine.
The ear cartilage, an elastic type, supports the external ear.

Osteoporosis

Osteoporosis signifies a gradual loss of bone mass, leading to weakened bones, increased susceptibility to fractures, and easier bone breaks.
Contributing factors include hormone deficiency, calcium and vitamin deficiency, physical inactivity, and lifestyle choices.

The Axial Skeleton

The Axial Skeleton comprises the Skull, the Vertebral Column, and the Bony Thorax.
It consists of 80 bones.

The Skull

The Skull is comprised of two sets of bones:
- The Cranium, which encloses the brain.
- The Facial bones, which house the eyes and provide structures for facial muscles.
Bones of the skull are connected by non-moving sutures, except for the mandible, which articulates at a freely moving joint.

Cranium/Cranial Bones

The Cranium is divided into the superior Cranial Vault or Calvaria and the Inferior Cranial Floor or Base.
The cranial floor encompasses three concavities that hold the brain: the Anterior, Middle, and Posterior fossa.

Cranial Bones

The cranium consists of four bones:
- The Frontal bone.
- The paired Parietal bones.
- The paired Temporal bones.
- The Occipital bone.

The Frontal Bone

The Frontal bone forms the anterior portion of the cranium, including the forehead, superior orbit, and the floor of the Anterior Fossa.
The Supraorbital foramens (notches) above each orbit allow passage for blood vessels and nerves.

The Parietal Bones

The Parietal bones constitute the superior sides of the cranium.
The Sagittal Suture represents the midline articulation point of the parietal bones.

The Temporal Bones

The Temporal bones make up the inferior sides of the cranium.
The Squamous Suture marks the point of articulation between the temporal and parietal bones.
The bridge-like Zygomatic process forms the cheekbone.
The Mandibular fossa is a rounded depression serving as the articulation site with the mandible.
The External Acoustic Meatus is a canal leading to the eardrum and middle ear.
The Styloid process serves as an attachment site for muscles and ligaments of the neck.
The Mastoid process provides an attachment site for muscles.
Mastoiditis, an infection of the mastoid process, can spread to the brain's meninges (brain coverings), resulting in Meningitis.
The Stylomastoid foramen allows passage for Cranial Nerve # VII.
The Jugular foramen provides passage for the internal jugular vein and cranial nerves IX, X, and XI.
The Carotid canal serves as a passage for the internal carotid artery.
The Internal acoustic meatus is a pathway for cranial nerves VII and VIII.
The Foramen Lacerum allows passage for the internal carotid artery and small nerves.

The Occipital Bone

The Occipital bone forms the posterior portion of the cranium.
It articulates with the Sphenoid bone anteriorly.
The Lambdoid Suture represents the articulation point between the occipital and parietal bones.
The Foramen Magnum provides a large opening for the spinal cord.
The Hypoglossal Canal serves as a passage for the hypoglossal nerve (cranial nerve #XII).
Occipital Condyles articulate with C1, the Atlas.

The Sphenoid Bone

The Sphenoid bone, bat-shaped, forms the anterior plateau of the middle cranial fossa, extending across the skull's width.
The Greater wings contribute to the orbital socket.
The Superior Orbital Fissures, jagged openings, allow passage of cranial nerves III, IV, V, and VI into the orbit to serve the eye.
The Inferior Orbital Fissures facilitate passage of the infraorbital vessels and cranial nerve #V.
The Sella Turcica (Turk's Saddle) lies in the central portion of the bone.
The seat of the saddle, the Hypophyseal fossa, houses the pituitary gland.
The Optic canals provide openings for the optic nerves.
The Foramen Rotundum and Ovale serve as openings for branches of the fifth cranial nerve.
The Foramen Spinosum allows passage for the Middle Meningeal Artery.

The Ethmoid Bone

The Ethmoid bone, anterior to the sphenoid, forms the roof of the nasal cavity, the upper nasal septum, and part of the medial orbital wall.
The Crista Galli, a vertical projection, serves as an attachment point for the dura mater of the brain, helping to secure it to the skull.
The Cribiform plates, bony plates lateral to the crista galli, hold the Olfactory foramina, facilitating the passage of olfactory fibers.
The crista galli and cribiform plates form the horizontal plate.
The Perpendicular plate forms the superior nasal septum.
The Lateral masses contribute to the medial orbital walls.
The Superior and Middle Nasal Conchae, also known as turbinates, aid the nasal cavity mucosa in warming and humidifying incoming air.

Facial Bones

The Facial bones comprise fourteen paired bones and two single bones: the Vomer and the Mandible.

The Mandible

The Mandible, the lower jawbone, articulates with the temporal bone via the only freely moving joint in the skull.
The Mandibular Body forms the chin.
The Mandibular condyles are articulation points with the temporal bone.

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Description

This quiz explores the microscopic structure of bone and the process of ossification. It covers the roles of various bone cells, the Haversian system, and the steps involved in endochondral ossification. Test your understanding of these fundamental concepts in bone biology.