Anatomy Review: Skeletal System (Midterm)

**A. Explain the functions of the skeletal system.** Sitting, standing, walking, picking up a pencil, and taking a breath all involve the skeletal system. Without the skeletal system, there would be no rigid framework to support the soft tissues of the body and no system of joints and levers to all...

**A. Explain the functions of the skeletal system.** Sitting, standing, walking, picking up a pencil, and taking a breath all involve the skeletal system. Without the skeletal system, there would be no rigid framework to support the soft tissues of the body and no system of joints and levers to allow the body to move. The term \'skeleton\" is derived from a Greek word meaning dried. But the skeleton is far from being dry and nonliving. Rather, the skeletal system consists of dynamic, living tissues that are able to grow, detect pain stimuli, adapt to stress, and undergo repair after injury. **2 Divisions of the Skeleton** **Axial skeleton**- the bones that form the ongitudinal axis of the body - longitudinal an **Appendicular Skeleton**- the bones that forms the limbs and girdles limos girdles **4 Structures of the Skeletal System** 1\. Bones 2\. Joints 3\. Cartilages 4\. Ligaments **FUNCTIONS OF THE SKELETAL SYSTEM:** 1\. **Support**. Rigid, strong bone is well suited for bearing weight and is the major supporting tissue of the body. Cartilage provides firm yet flexible support within certain structures, such as the nose, external ear, thoracic cage, and trachea. Ligaments are strong bands of fibrous connective tissue that attach to bones and hold them together. 2\. **Protection**. Bone is hard and protects the organs it surrounds. For example, the skull encloses and protects the brain, and the vertebrae surround the spinal cord. The rib cage protects the heart, lungs, and other organs of the thorax. 3\. **Movement**. Tendons, strong bands of connective tissue, attach skeletal muscles to bones. Thus, contraction of skeletal muscles pulls the tendons, which moves the bones. In this way, we can move our appendages for normal body movements. Joints where two or more bones come together, allow movement between bones. Ligaments allow some movement between bones but prevent excessive movement 4\. **Storage**. Some minerals in the blood-principally, calcium and phosphorus-are stored in bone. Should blood levels of these minerals decrease, the minerals are released from bone into the blood. Adipose tissue is also stored within bone cavities. If needed, the lipids are released into the blood and used by other tissues as a source of energy. 5\. **Blood cell production**. Many bones contain cavities filled with red bone marrow, which produces blood cells and platelets **EXTRACELLULAR MATRIX** The bone, cartilage, tendons, and ligaments of the skeletal system are all connective tissues. Their characteristics are largely determined by the composition of their extracellular matrix. The matrix always contains collagen, ground substance, and other organic molecules, as well as water and minerals. **CATEGORIES OF BONES:** **Long bones** are longer than they are wide. This shape enhances their function in movement of appendages. Most of the bones of the upper and lower limbs are long bones. **Short bones** are approximately as wide as they are long examples are the bones of the wrist and ankle. Short bones help transfer force between long bones **Flat bones** have a relatively thin, flattened shape. Flat bones are well-suited to providing a strong barrier around soft organs such as the brain and heart. Examples of flat bones are certain skull bones, the ribs, the scapulae (shoulder blades), and the sternum. **Irregular bones** include the vertebrae and facial bones, which have shapes that do not fit readily into the other three categories. These bones tend to have specialized functions, such as providing protection while allowing bending and flexing of certain body regions such as the spine. **ANATOMY OF LONG BONE** A long bone serves as a useful model for illustrating the parts of a typical bone. **GROSS ANATOMY:** - - - - - - - - - - **Histology of the Bone** - - - - - - Bone tissue found throughout the skeleton is divided into two major types, based on the histological structure **Compact bone** - Compact bone or cortical bone, (figure 6.3) forms the perimeter of the diaphysis of a long bone and the thinner surfaces of all other bones. Compact bone has more matrix and is denser, with fewer pores than spongy bone. As you can see in figure 6.3, compact bone has a predictable pattern of repeating units. These units are called osteons. Each osteon consists of concentric rings of lamellae surrounding a central canal, or Haversian canal - **Spongy bone** - Spongy bone is very porous and is located in the epiphyses of long bones and lines the medullary cavity of long bones. It has less bone matrix and more open space than compact bone. Spongy bone consists of delicate interconnecting rods or plates of bone called trabeculae which resemble the beams or scaffolding of a building - **Bone Ossification** - - - - - - - - - **Bone remodeling** - - - **Bone Growth** - - - - - **Bone Repair** - - - **Types of Bone Fractures:** Severity to the soft tissues surrounding the bone: - - - - - - - Fractures that are classified according to the direction of the fracture within the bone: - - - - **Bone and Calcium Homeostasis** - - PTH works through three simultaneous mechanisms to increase blood calcium levels. 1\. PTH indirectly stimulates osteoclasts to break down bone, which releases stored calcium into the blood. 2\. PTH stimulates the kidney to take up calcium from the urine and return it to the blood. 3\. PTH stimulates the formation of active vitamin D, which, in turn, promotes increased calcium absorption from the small intestine. **Bone Anatomy** It is traditional to list 206 bones in the average adult skeleton, although the actual number varies from person to person and decreases with age as some bones fuse. Anatomists use several common terms to describe the features of bones: **BONE MARKINGS** - are projections and depressions found on bones, which help us to identify the location of other body structures, such as muscles. **2 Categories of Bone Markings:** - - **Common Bone Markings:** ***Major Features:*** - Examples: - Example: - Examples: - Examples: - Examples: - - - - Examples: - Examples: - - - Examples: - - **Openings or Depressions:** - Examples: - Examples: - Examples: - Examples: - Examples: - Examples: - - - **AXIAL SKELETON** The 22 bones of the skull are divided into those of the braincase and those of the face. The braincase (neurocranium), which encloses the cranial cavity, consists of 8 bones that immediately surround and protect the brain; 14 facial bones form the structure of the face Thirteen of the facial bones are rather solidly connected to form the bulk of the face. The mandible, however, forms a freely movable joint with the rest of the skull. There are also three auditory ossicles in each middle ear (six total). **Skull Anatomy on Lateral View:** - - - - - - - - - - - - - - - - - **SUTURES OF THE SKULL** The sutures of the skull, also referred to as the cranial sutures, are fibrous joints that Connect the bones of the skull. They appear as intricate thin lines that mark the adherence between the bones and the growth and closure of the cranial fontanelles. - - - - - - - - - **Skull Anatomy on Front View:** - - - - - - - - - - - - - - **Inferior of the Cranial Cavity:** When the floor of the cranial cavity is viewed from above with the roof cut away (figure it can be divided roughly into three cranial fossae (anterior, middle, and posterior), which are formed as the developing skull conforms to the shape of the brain. The bones forming the floor of the cranial cavity, from anterior to posterior, are the frontal, ethmoid, sphenoid, temporal, and occipital bones. Several foramina can be seen in the floor of the middle fossa. These allow nerves and blood vessels to pass through the skull. **Anatomy of the Inferior Cranial Cavity:** - - - **Base of the Skull** Many of the same foramina that are visible in the interior of the skull can also be seen in the base of the skull, when viewed from below, with the mandible removed. Other specialized structures, such as processes for muscle attachments, can also be seen. The foramen magnum is located in the occipital bone near the center of the skull base. **Parts seen when viewed from below:** - - - - - - The hard and soft palates separate the nasal cavity and nasopharynx from the mouth, enabling us to chew and breathe at the same time. **The Hyoid bone** The hyoid bone is an unpaired, U-shaped bone. It has the unique distinction of being the only bone in the body that does not articulate with another bone. Muscles and ligaments attach it to the skull. The hyoid bone provides an attachment for some tongue muscles, and it is an attachment point for important neck muscles that elevate the larynx (\"voicebox\") during speech or swallowing. **The Vertebral Column performs the following five major functions:** - - - - - **Abnormalities of the Vertebral Column:** - - - **Anatomy of the Vertebrae:** - - - - - - Has two parts: - - - - - - - **Regional Differences in Vertebrae** The cervical vertebrae have very small bodies, except for the atlas, which has no body Because the cervical vertebrae are relatively delicate and have small bodies, dislocations and fractures are more common in this area than in other regions of the vertebral column. **2 Main parts of the Cervical vertebra:** - - The **thoracic vertebrae** possess long, thin spinous processes that are directed inferiorly. The thoracic vertebrae also have extra articular facets on their lateral surfaces that articulate with the ribs. The **lumbar vertebrae** have large thick bodies and heavy, rectangular transverse and spinous processes. Because the lumbar vertebrae carry a large amount of weight, they have massive bodies (Low back pain and other medical ailments are more common in this area than in other regions of the column. The five sacral vertebrae are fused into a single bone called the **sacrum**. The spinous processes of the first four sacral vertebrae form the median sacral crest. The spinous process of the fifth vertebra does not form, leaving a sacral hiatus at the inferior end of the sacrum, which is often the site of \"caudal\" anesthetic injections given just before childbirth. The anterior edge of the body of the first sacral vertebra bulges to form the **sacral promontory**, a landmark that can be felt during a vaginal examination. It is used as a reference point to determine if the pelvic openings are large enough to allow for normal vaginal delivery of a baby. The **coccyx**, or tailbone, usually consists of four more-or-less fused vertebrae. The vertebrae of the coccyx do not have the typical structure of most other vertebrae. They consist of extremely reduced vertebral bodies, without the foramina or processes, usually fused into a single bone. The coccyx is easily fractured when a person falls by sitting down hard on a solid surface or in women during childbirth. **Sternum** The sternum, or breastbone, is divided into three parts: - - - - - The sternum resembles a sword, with the **manubrium** forming the handle, the **body** forming the blade, and the **xiphoid process** forming the tip. At the superior end of the sternum, a depression called the **jugular notch** is located between the ends of the clavicles where they articulate with the sternum. A slight elevation, called the **sternal angle**, can be felt at the junction of the manubrium and the body of the sternum. This junction is an important landmark because it identifies the location of the second rib. This identification allows the ribs to be counted; for example, it can help a health professional locate the apex of the heart, which is between the fifth and sixth ribs. **APPENDICULAR SKELETON** **Pectoral Girdle** The **Pectoral Girdle, or shoulder girdle**, consists of four bones, two scapulae and two clavicles, which attach the upper limb to the body. - - - - - - **UPPER LIMB** The upper limb consists of **army forearm, wrist, and hand** the elbow; it contains: - - - - - **Forearm** The forearm has two bones: - - - - - - - **Wrist** The wrist is a relatively (short region between the forearm and the hand, it is composed of: **The Eight Carpal bones:** 1. 2. 3. 4. 5. 6. 7. 8. 9. The carpal bones are arranged in two rows of four bones each and form a slight curvature that is concave anteriorly and convex posteriorly. **Hand** - - - **Pelvic Girdle** The pelvic girdle is the place where the dower limbs attach to the body, it consists of: 7 - - - - - - - The **ilium** is the most superior, the **ischium** is inferior and posterior, and the **pubis** is inferior and anterior. An **iliac crest** can be seen along the superior margin of each ilium. The **pelvic inlet** is formed by the pelvic brim and the sacral promontory. The **pelvic outlet** is bounded by the ischial spines, the pubic symphysis, and the coccyx **LOWER LIMB** **Thigh** - - - - - - **Leg** The leg is the region between the knee and the ankle It contains two bones: - - - **JOINTS** - - - - - - - **Classification of Joints:** - - **All synovial joints have four distinguishing features:** - - - - **Types of Movements:** **MOVEMENT** 1. - - 2. 3. 4. 5. 6. 7. 8. 9. 10. - 11. 12. 13. 14. 15. 16. 17. **Inflammatory Conditions Associated with Joints** - - - - - **Clinical Forms of Arthritis** - - - - - - - - - -