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The Skeletal System Notes H Skeletal System.htm
Terminology 1 Condyle – Rounded prominence 2 Facet – Smooth articular surface 3 Fissure – Narrow opening 4 Foramen – Opening or hole through bone 5 Fossa – Depression or groove
6 Process – Any bone projection 7 Spine – A narrow or pointed projection 8 Trochanter – A large, blunt process Notes H Skeletal Features.htm
9).Tubercle – A small, rounded process 10).Tuberosity – A rounded, elevated area of a bone that is usually roughened
Types of bones 4 types of bones. Long bones - longer than they are wide. Short bones - equal in length and width. Flat bones - thin and flat. Irregular bones do not fit into any of these categories.
Bone Structure The shaft of the long bone is called the diaphysis. The extreme ends of the bones are known as the epiphyses. The diaphysis is between the two epiphyses.
Epiphysis of one bone meets the epiphysis of another bone is called a joint. Cartilage in joint known as the articular cartilage.
Bone - covered by a layer of connective tissue (periosteum). Provides nourishment attaches ligaments and tendons.
Two types of bone tissue in the diaphysis. Compact bone is tightly packed and forms the walls of the diaphysis. Spongy bone is less compact and is found in the diaphysis.
Within the spongy bone is red marrow. Within the diaphysis is a chamber called the medullary cavity. This cavity has yellow marrow which is used for energy storage.
Leukemia Red marrow - makes red blood cells (hematopoiesis), white blood cells, and platelets. When white blood cells can’t fight off infection, leukemia develops. Treatment for leukemia - injecting new bone marrow into the patient.
*Bone cells There are three types of bone cells. 1 Osteoblasts - come from embryonic cells and found on surface of bone tissue. They lay bone down around themselves - become surrounded by bone matrix. Then they are called 2 osteocytes.
3 Osteoclasts are found in the bone tissue and are involved with secretion of a substance that breaks down the bones. Osteoclasts help to break down the bone so that osteoblasts can lay new bone. This is how a bone grows.
Under the microscope Osteocytes are found in spaces called lacunae, which are found between lamellae. These lamellae are layered in circles around canals known as Haversian canals.
Bone Growth 2 forms of development. 1 Intramembranous bones - cells develop between sheetlike layers of connective tissue. 2 Endochondral bones - masses of cartilage are later replaced by bone tissue.
Intramembraneous bones - bones of the skull. Connective tissue appears where the bones will eventually be. Some of that connective tissue differentiates into the osteoblasts, which lay down bone.
In endochondral bone (most other bones) - masses of cartilage have same basic shape as future bones. The cartilage cells die - osteoblasts replace them. Happens in two stages - primary and secondary ossification centers.
When bone nears end of early development, a narrow band of cartilage remains between epiphyses and the diaphysis (epiphyseal plate) These are growth plates - located at each end of the bone. Determines how long your bones will be.
Growth plate injuries can happen. This is when the growth plate area is broken. In severe cases (only in children), it can stunt growth of the bone. When these growth plates close, you are done growing.
Osteoblasts and osteoclasts - lay down bone and breaking down bone. Once the epiphyseal plate is gone - done growing. The osteoblasts and osteoclasts are important in broken bones.
Broken bones Complete fractures - bone is completely broken. Greenstick fracture - fracture is not completely through. Comminuted fracture - bone is shattered.
Organization of Skeletal System Skeleton is divided into two parts. 1 Axial skeleton - bones that are located medially. 2 Appendicular skeleton - bones that are responsible for appendages.
Axial skeleton - skull, the hyoid bone, vertebral column, and thoracic cage. Appendicular skeleton - the pectoral girdle, upper limbs, pelvic girdle, and lower limbs.
Axial Skeleton * A Skull - Consists of 22 bones that are joined by sutures. Sutures are rigid, narrow joints. The “soft spot” in infants is an area where the sutures have not fully closed yet.
Sinuses - chambers in the skull that are lined with mucous membranes. Drain fluids, reduce the weight of the skull, and resonate sound from the voice. Sinuses can become infected (sinus infection).
Bones of the skull The cranium encloses and protects the brain. It is made of 8 bones. 1 Frontal bone – large bone that forms the anterior part of the skull above the eyes. Contains the eye sockets (orbits).
Located above each orbit is the supraorbital foramen which is a hole through which blood vessels and nerves travel. The frontal bone also has the frontal sinuses.
2 The parietal bones (2) Two parietal bones - one left and one right. Form the lateral part of the cranium. Meet at the top (the sagittal suture); meet the frontal bone at the coronal suture.
3 Occipital bone - forms the posterior wall of the cranium. Meets the parietal bones at the lambdoidal suture. Foramen magnum - large opening that allows spinal cord to pass between the cranium and the spinal cavity.
4 Temporal bones (2) - on either side of the cranium (think temples!!) External auditory meatus located here and is the opening to the inner ear. Zygomatic arch (your cheekbone) joins the temporal bone to the zygomatic bone.
The mastoid process is located posterior and is the location of the attachment of neck muscles. The styloid process is the location of the attachment of the muscles of the tongue.
External auditory meatus
5 Sphenoid bone- wedged between other bones in the skull. Home of the optic foramen, where the optic nerve passes to go to the brain. Pituitary gland is housed in the sella turcica in the sphenoid bone. Sphenoidal sinuses here.
Sella Turcica (means “Turkish saddle”)
6 Ethmoid bone - anterior to the sphenoid. Mostly internal and forms part of nasal cavity. Ethmoid forms into the superior and middle nasal conchae (into the nostrils) Ethmoidal sinuses here.
* B Facial bones - 13 immovable bones in the face and a movable lower jaw. Support the face and provide attachments for the muscles that control facial expressions.
1 Maxillary bones - two bones located on side of the face that form the upper jaw. Maxillary sinuses (the largest ones) are located here. The roof of the mouth (including both palates) are formed by these bones.
2 Palatine bones - 2 L-shaped bones that are located posterior to the maxillary bones. Form the posterior roof of the mouth.
3 Zygomatic bones – 2 bones that are found on the side of the face and form the cheekbones. Forms the zygomatic arch with the temporal bones.
4 Nasal bone - the two bones meet at the midline to form the bridge of the nose. The rest of the nose is formed from cartilage.
5 Lacrimal bones – 2 bones that are posterior and lateral to the nasal bones. Lacrimal means tears, so they are located in approximately the same area as your tear ducts.
6 Vomer (1) - Located along the midline of the nasal cavity. The nasal septum divides the cavity into the left and right sides. A deviated septum is when the cavity is not divided into equal halves.
7 Inferior nasal conchae (2) - Found below the superior and middle conchae of the ethmoid bone.
Inferior nasal conchae
8 Mandible - lower jaw bone that articulates with the temporal bones. The only movable bone of the skull.
The hyoid bone This bone does not articulate with any other bone in the entire body. It supports the tongue and provides attachment for some of the muscles of the tongue.
C Vertebral column - support for the trunk of the body. It runs from the skull to the pelvis. The bones that make up this column are known as vertebrae and are separated from each other by intervertebral discs.
A herniated disk happens when the disk breaks and puts pressure on the spinal nerve.
The 33 vertebrae are divided into regions. Cervical vertebrae (7) are in the neck. Thoracic vertebrae (12) in the thorax.
Lumbar vertebrae (5) in the lower trunk Sacral vertebrae (5) are fused (sacrum) The coccygeal (3-5) are fused (coccyx). Each region has a curve associated with it.
A vertebrae made up mostly of the body. Middle - vertebral foramen that the spinal cord passes through. Spiny part of the vertebrae called the spinous process. Connected to the body by pedicle. Transverse process are lateral projections.
The cervical vertebrae have two unique members. The atlas is the first vertebrae and it articulates with the skull. The second vertebrae is the axis and allows the nodding of the head by articulating with the atlas.
The thoracic vertebrae are larger than the cervical vertebrae. The lumbar vertebrae are thicker than the thoracic. The sacrum is triangular as a result of the fusion. The coccyx is your tailbone.
D Thoracic cage - formed from the sternum and ribs. Sternum is the breastbone and located in the middle of the chest. It is made of three parts; the superior manubrium, the body, and the inferior xiphoid process.
Ribs (12 pairs) attaches to individual thoracic vertebra sternum (by costal cartilage) First seven pairs of ribs are true ribs - attached at both points. Five pairs are false ribs have very little connection. Last two - floating ribs (no cartilage)
Appendicular Skeleton A The Pectoral Girdle - shoulder girdle is made up of two clavicles (collarbones) and two scapulae (shoulder blades) Scapulae have two processes (the coracoid process and the acromion process) allows for attachment of muscles.
* B The upper limb - humerus extends from scapula to elbow. The head of the humerus fits into the glenoid cavity of the scapula. The two tubercles (the greater and lesser) provide attachments for muscles.
Lower end of the humerous - two condyles that articulate with radius and ulna. Two fossas (the coronoid on the anterior side and the olecranon on the posterior side) allow for elbow movements.
Radius - bone located on thumb side of forearm; extends from elbow to wrist. Head of radius articulates with humerus and a notch of the ulna. Radial tuberosity allows for muscle attachment and styloid process allows for wrist ligament attachment.
Ulna is longer than radius and overlaps the end of the humerus. Proximal end - the ulna has a trochlear notch that articulates with the humerus. Two processes on either end of the notch; the olecranon process and the coronoid process.
Distal end of ulna is the head that articulates with the radius. Ulna also has a styloid process that allows for attachment of the wrist ligaments.
Hand is composed of wrist, palm, and five fingers. Wrist is made up of eight carpal bones. The eight bones of the wrist are the lunate, hamate, triquetrum, pisiform, scaphoid, capitate, trapezoid, and trapezium.
Palm consists of five metacarpal bones. Finger bones are known as the phalanges. Each finger has proximal, middle, and distal phalanx (the thumb does not have the middle)
C Pelvic girdle - 2 coxal bones that articulate with each other anteriorly and the sacrum posteriorly. Sacrum, coccyx, and pelvic girdle together form pelvis. Pelvis supports trunk of the body, provides attachments for lower limbs, and protects organs located in that area.
* Coxal bone has three parts. Ilium is part of the bone that you think of as the hip. Flares outward and forms the bony prominence of the hip. Top of this is called the iliac crest. Ilium joins the sacrum at the sacroiliac joint and has anterior superior iliac spine which provides attachments for muscles.
Ischium forms the lowest portion of the coxal bone. Ischial tuberosity points posteriorly and downward and provides attachment for muscles and ligaments. Where the ilium meets the ischium is a projection called the ischial spine.
Pubis is anterior part of the coxal bone. 2 pubic bones join at midline, forming a joint called the symphysis pubis. Angle of these bones below the symphysis pubis is called pubic arch. Obturator foramen is found in pelvic girdle and is the largest in the body.
D Lower limbs form thigh, leg, and foot. Femur is longest bone in the body and extends from hip to the knee. Head of the femur fits in the acetabulum of the coxal bone. On head is fovea capitis which allows attachment of a ligament.
Below the head – 2 processes; the greater trochanter and the lesser trochanter. Distal end of femur - 2 condyles (lateral and medial) that articulate with tibia of the leg. Patella (kneecap) articulates with femur at distal end.
Tibia – shinbone; larger of two lower leg bones (located medially). Proximal end has medial and lateral condyles that articulate with the condyles of the femur. Below condyles is tibial tuberosity. Distal end - medial malleolus.
Fibula - smaller lower leg bone. Has a head at the proximal end and a lateral malleolus at the distal end. The lateral malleolus is responsible for the bump you feel on the side of your ankle.
Foot - 7 tarsal bones (calcaneous, talus, navicular, cuboid, lateral cuneiform, intermediate cuneiform, and the medial cuneiform) Talus moves freely where it meets the fibula and tibia. Calcaneous - largest (heel bone)
Tarsal bones articulate with metatarsals. 5 metatarsals articulate with phalanges (the toes). 3 phalanges for each toe; the proximal, middle, and distal phalange. Big toe does not have a middle one.
Diseases 1 Achondroplasia – form of dwarfism. Due to cartilage converting to bone during development. Normal-size trunk and head; short extremities.
Note the shortened femurs
2 Osteoporosis – occurs when the rate of bone formation and bone resorption changes. Results in fragile bones that break easily.
3 Rheumatoid Arthritis – cartilage and dense connective tissue breakdown easily. The joint eventually fuses with the bone. Autoimmune disease – person’s immune system attacks itself.