Notes #1, Lab Exam #2 2022 Update PDF

# Microscopic Structure of the Bone - marrow is only found in the epiphyses spaces in the spongy bone. - A central Haversian canal runs parallel to the long axis of the bone. - It carries blood vessels nerves, and lymph vessels. - Osteocytes (mature bone cells) are found in the lacunae, chambers ar...

# Microscopic Structure of the Bone - marrow is only found in the epiphyses spaces in the spongy bone. - A central Haversian canal runs parallel to the long axis of the bone. - It carries blood vessels nerves, and lymph vessels. - Osteocytes (mature bone cells) are found in the lacunae, chambers arranged in concentric circles (Lamallae) around the central canal. - The central canal and all the concentric lamallae are called an Osteon or a Haversian system. - Canaliculi are tiny canals radiating from the central canal and are a communication and transport network for nutrients. - Volksmann's canals are perpendicular to the shaft, come from the periosteum, and extend to the bone marrow cavity and connect the central cavities to each other. # Ossification of Bone - Endochondral ossification uses hyaline bones as patterns for bone formation. - From the primary ossification center the steps to bone formation are: - Periosteum replaces perichondrium. - Osteoblasts secrete bone around hyaline bone model. - Cartilage in shaft center calcifies and hollows forming a cavity. - A periosteal bud (osteoblasts, osteoclasts, blood vessels, red marrow, and nerves) invades cavity forming a medullary cavity on either side of the primary ossification center. - During bone growth the medullary cavity grows longer and larger. - After adolescence the epiphyseal plate of ossifying cartilage is replaced by a calcified bony epiphyseal line. # Cartilage - Cartilage is mostly water with differing amounts of elastic, reticular or collagen fibers. - Cartilage has an outer covering of perichondrium, which plays a role in growth and repair. - Cartilage also has no nervous enervation and is relatively avascular. - There are three types of cartilage: Elastic, Hyaline and Fibrocartilage. ## Cartilages of the Skeleton 1. Articular cartilage, which is hyaline, is found at the epiphysis of long bones. 2. Costal cartilage, which is hyaline, connects the ribs to the sternum (breastbone). 3. Laryngael cartilage, which is hyaline, constructs the voice box in the larynx. 4. Tracheal and Bronchial cartilages, which are hyaline, reinforce passageways of the respiratory system. 5. Nasal cartilage, which is hyaline, supports the external nose. 6. Intervertebral discs cartilage, which are fibrocartilage, separate and cushion the bones of the spine. 7. The Ear cartilage, which is elastic, supports the external ear. # Osteoporosis - Osteoporosis is the gradual loss of bone mass, which results in the weakening of bones, bone breaks and fractures more easily. - Causes are hormone deficiency, calcium and vitamin deficiency, physical inactivity, vices. # The Axial Skeleton - The Axial Skeleton consists of the Skull, the Vertebral Column, and the Bony Thorax. - Consists of 80 bones. ## The skull consists of two sets of bones: 1. The Cranium which encloses the brain. 2. The Facial bones which present the eyes, and have structures for the facial muscles. - Bones of the skull are connected by non-moving sutures, except for the mandible, which is attached 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 has three concavities that hold the brain: the Anterior, Middle and Posterior fossa. ## The cranium consists of four bones: - The Frontal, the paired Parietals, the paired Temporals, and the Occipital. ### The Frontal bone - The Frontal bone is the anterior portion of the cranium and contains the forehead, superior orbit and the floor of the Anterior Fossa. - The Supraorbital foramens (notch) are openings above each orbit which allow blood vessels and nerves to pass. ### The Parietal bones - The Parietal bones make up the superior sides of the cranium. - The Saggital Suture is 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 is the point of articulation of the temporal and parietal bones. - The bridge-like Zygomatic process forms the cheekbone. - The Mandibular fossa is a rounded depression that is the site of articulation with the mandible. - The External Acoustic Meatus is a canal leading to the eardrum and middle ear. - The Styloid process is an attachment site for muscles and ligaments of the neck. - The Mastoid process is an attachment site for muscles. - Mastoidistis is an infection of the mastoid process of the temporal bone. - Infection in this site can spread to the meninges of the brain, the brain coverings, this is called Meningitis. - The Stylomastoid foramen is an opening for Cranial Nerve # VII. - The Jugular foramen is an opening for the internal jugular vein and cranial nerves IX, X, and XI. - The Carotid canal is an opening for the internal carotid artery. - The Internal acoustic meatus is a passageway for cranial nerves VII, and VIII. - The Foramen Lacerum is an opening for the internal carotid artery and small nerves. ### The Occipital bone - The Occipital bone makes up the posterior portion of the cranium. - The occipital bone joins the Sphenoid bone anteriorly. - The Lamboid Suture is point of articulation between the occipital and parietal bones. - The Foramen Magnum is the large opening for the spinal cord. - The Hypoglossal Canal is a passageway for the hypoglossal nerve (cranial nerve #XII). - Occipital Condyles articulate with C1 the Atlas. ### The Sphenoid bone - The Sphenoid bone is a bat-shaped bone forming the anterior plateau of the middle cranial fossa, runs along the width of the skull. - The Greater wings form part of the orbital socket. - The Superior Orbital Fissures are jagged openings that allow passage of cranial nerves III, IV, V and VI into orbit to serve eye. - The Inferior Orbital Fissures allow 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 holds the pituitary gland. - The Optic canals are openings for the optic nerves. - The Foramen Rotundum and Ovale are openings for branches of the fifth cranial nerve. - The Foramen Spinosum is an opening for the Middle Meningeal Artery. ### The Ethmoid bone - The Ethmoid bone is anterior to the sphenoid and forms the roof of the nasal cavity, upper nasal septum and part of the medial orbital wall. - The Crista Galli is a vertical projection and attachment point for the dura mater of the brain, helping to secure it to the skull. - The Cribiform plates are bony plates lateral to the crista galli, which hold the Olfactory foramina, which allow for passage of the olfactory fibers. - The crista galli and the cribiform plates form the horizontal plate. - The Perpendicular plate forms the superior nasal septum. - The Lateral masses form part of the medial orbital walls. - The Superior and Middle Nasal Conchae are turbinates which help the mucosa in the nasal cavity warm and humidify incoming air. ## Facial bones - The Facial bones are made up of seven paired bones (14) and two single bones, the Vomer and the Mandible. ### The Mandible - The Mandible is the lower jawbone and 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. - The Conoid process is an attachment point for muscles. - The Mental Foramen is an opening for mental blood vessels and nerves of lower jaw. - The Alveolar margin contains the superior sockets for teeth. - The Mandibular symphysis denotes point of mandibular fusion. - The Mandibular Foramen is an opening for cranial nerve #V.