Human Anatomy Lab 2 PDF

Lab 2: Introduction to the Skeletal System Background Information Bone, or osseous tissue, is a hard, dense connective tissue that forms most of the adult skeleton. In the areas of the skeleton where bones move (for example, the ribcage and joints), cartilage, a semi-rigid form of connective tissue,...

Lab 2: Introduction to the Skeletal System Background Information Bone, or osseous tissue, is a hard, dense connective tissue that forms most of the adult skeleton. In the areas of the skeleton where bones move (for example, the ribcage and joints), cartilage, a semi-rigid form of connective tissue, provides flexibility and smooth surfaces for movement. The skeletal system is composed of bones and cartilage and performs several critical functions for the human body including: supporting the body, facilitating movement, protecting internal organs, producing blood cells, and storing and releasing minerals and fat. Major Divisions of the Body The skeletal system includes all of the bones, cartilages, and ligaments of the body that support and give shape to the body and body structures. The skeleton consists of the bones of the body. For adults, there are 206 bones in the skeleton. Younger individuals have higher numbers of bones because some bones fuse together during childhood and adolescence to form an adult bone. The primary functions of the skeleton are to provide a rigid, internal structure that can support the weight of the body against the force of gravity, and to provide a structure upon which muscles can act to produce movements of the body. The skeleton is subdivided into two major divisions—the axial and appendicular. The axial skeleton forms the vertical, central axis of the body and includes all bones of the head, neck, chest, and back. It serves to protect the brain, spinal cord, heart, and lungs. It also serves as the attachment site for muscles that move the head, neck, and back, and for muscles that act across the shoulder and hip joints to move their corresponding limbs. The axial skeleton of the adult consists of 80 bones, including the skull, the vertebral column, and the thoracic cage. The appendicular skeleton includes all bones of the upper and lower limbs, plus the bones that attach each limb to the axial skeleton. There are 126 bones in the appendicular skeleton of an adult. These bones are divided into two groups: the bones that are located within the limbs themselves, and the girdle bones that attach the limbs to the axial skeleton. The bones of the shoulder region form the pectoral girdle, which anchors the upper limb to the thoracic cage of the axial skeleton. The lower limb is attached to the vertebral column by the pelvic girdle. Axial and Appendicular Skeleton. Bone shapes The 206 bones that compose the adult skeleton are divided into five categories based on their shapes. Their shapes and their functions are related such that each categorical shape of bone has a distinct function. Long Bones A long bone is one that is cylindrical and is longer than it is wide. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges). Long bones function as levers; they move when muscles contract. Short Bones A short bone is one that is cube-like in shape, being approximately equal in length, width, and thickness. The only short bones in the human skeleton are in the carpals of the wrists and the tarsals of the ankles. Short bones provide stability and support as well as some limited motion. Flat Bones The term “flat bone” is somewhat of a misnomer because, although a flat bone is typically thin, it is also often curved. Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs. Irregular Bones An irregular bone is one that does not have any easily characterized shape and therefore does not fit any other classification. These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many facial bones, particularly the ones containing sinuses, are classified as irregular bones. Sesamoid Bones A sesamoid bone is a small, round bone that, as the name suggests, is shaped like a sesame seed. These bones form in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint. Sesamoid bones protect tendons by helping them overcome compressive forces. Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. The patellae (singular = patella) are the only sesamoid bones found in common with every person. Gross Anatomy The structure of a long bone allows for the best visualization of all of the parts of a bone (Figure 6.3). A long bone has two major parts: the diaphysis and the epiphysis. The diaphysis is the tubular shaft that runs between the proximal and distal ends of the bone which are called epiphyses. The hollow region in the diaphysis is called the medullary cavity, which is filled with yellow marrow in adults. The walls of the diaphysis are composed of dense and hard compact bone. Figure 6.3 Anatomy of a long bone. The medullary cavity has a delicate membranous lining called the endosteum (end- = “inside”; oste- = “bone”), where bone growth, repair, and remodeling occur. The outer surface of the bone is covered with a fibrous membrane called the periosteum (peri- = “around” or “surrounding”). The periosteum contains blood vessels, nerves, and lymphatic vessels that nourish compact bone. Tendons and ligaments also attach to bones at the periosteum. The periosteum covers the entire outer surface except where the epiphyses meet other bones to form joints (Figure 6.3). In this region, the epiphyses are covered with articular cartilage, a thin layer of cartilage that reduces friction and acts as a shock absorber. Flat bones, like those of the cranium, consist of a layer of diploë (spongy bone), lined on either side by a layer of compact bone (Figure 6.4). The two layers of compact bone and the interior spongy bone work together to protect the internal organs. If the outer layer of a cranial bone fractures, the brain is still protected by the intact inner layer. Figure 6.4 Anatomy of a Flat Bone. This cross-section of a flat bone shows the spongy bone (diploë) lined on either side by a layer of compact bone. Bone Features The surface features of bones vary considerably, depending on the function and location in the body. There are three general classes of bone markings: (1) articulations, (2) projections, and (3) holes. As the name implies, an articulation is where two bone surfaces come together. These surfaces tend to conform to one another, such as one being rounded and the other cupped, to facilitate the function of the articulation. A projection is an area of a bone that projects above the surface of the bone. These are the attachment points for tendons and ligaments. In general, their size and shape is an indication of the forces exerted through the attachment to the bone. A hole is an opening or groove in the bone that allows blood vessels and nerves to enter the bone. As with the other markings, their size and shape reflect the size of the vessels and nerves that penetrate the bone at these points. Table 6.1 lists and describes the major bone features. Table 6.1 Bone Features Marking Description Example Head Prominent rounded surface Head of femur Facet Flat surface Articular facets of vertebrae Condyle Rounded surface Occipital condyle Process Projection from the bone Spinous process of vertebrae Spine Short, sharp projection Transverse process of vertebrae Tubercle Small, rounded process Ischial spine Tuberosity Large, rough surface of a bone Tubercle of humerus Line Smaller elevated ridge of bone Temporal lines of parietal bone Crest Larger elevated ridge of bone Iliac crest Fossa Larger pit in a bone Mandibular fossa Fovea Smaller pit in a bone Fovea capitis of femur Sulcus Groove Sigmoid sulcus of temporal bone Canal Small passage in bone Auditory canal Fissure Slit through bone Inferior orbital fissure Foramen Hole through bone Foramen magnum Meatus Opening into a canal External auditory meatus Sinus Open space in bone Nasal sinus Lab 2 report: 1-Identify whether the following bones are a part of the axial or appendicular skeleton by writing thecorrect region on the provided blank. A. Sternum B. Humerus C. Skull D. Ribs E. Femur F. Carpals G. Clavicle 2-Provide one general function of the axial skeleton that is not a function of the appendicular skeleton. 3- Complete the table below on bone shapes. Bone Shape Description Examples Long Short Flat Irregular Sesamoid 4-Name 3 Bone surface marking allows passage for blood vessels and nerves 1- 2- 3- 5- Name 3 Bone surface marking found on vertebrae 1- 2- 3-