BY 30 – Fall 2001
12.1.
Functions of the Skeletal System
a. Each of the body’s 206 bones is considered to be a(n) ___________________, because they contain __________________ tissue types functioning together, the most important being _____________________ tissue. Taken together, all the bones of the body make up the _______________________________.
b. The skeletal system serves a number of functions in the body including ____________________________; ________________________________; ____________________________; ________________________________; and _______________________________.
c. Movement of the body involves ______________________ muscles, which attach to bones via ______________________. In this case, the bones act as ____________________ allowing body parts to be moved.
d. Bones contain virtually all the body’s supply of many important elements such as _______________________, _________________________, and ___________________________. These elements move back and forth between bone and ___________________________.
e. The process of blood cell formation, known as _____________________ takes place within bone _________________________.
12.2. Classification of Bones
a. Bones are classified as _____________________, _____________________, ______________________, and _______________________.
b. A _______________________ bone is one that is much longer than its width. Examples include limb bones such as the ____________________________, ____________________________, _______________________________ or ________________________________.
c. A ___________________ bone is one that is thin. Examples include bones of the _________________________ or the ___________________________.
12.3. Bone
Structure: Gross Anatomy
a. A long bone consists of three basic regions called the ___________________, _______________________ and ________________________. Of these, it is the _____________________ that forms the central shaft or body of the bone and contains a central _____________________________.
b. The diaphysis contains mostly ______________________ bone which contains few internal spaces and no _______________________ filled spaces.
c. The portion of a bone which articulates with other bones is called the ________________________, of which each bone typically has ___________. In these portions of the bone, the outer part consists of compact bone while the interior consists of ____________________ bone. This type of bone consists of structures called ________________________ with __________________ in between. Finally ______________________ is found on the very ends of the bone which functions to reduce ________________________ and absorb __________________________ at joints.
d. The ___________________________ is found at the junction of epiphysis and diaphysis. In a growing bone, it is the region where the ___________________ is found.
e. Unlike long bones, flat bones consist of two flat plates of _________________ bone with spongy bone in the middle referred to as the ___________________.
f. Bone marrow comes in two types called ________________________ marrow and _____________________ marrow. Of the two, it is the ______________ marrow in which ____________________________ takes place. In the infant, virtually all bone marrow is red, but in the adult, red bone marrow is largely restricted to the marrow of __________________________________ and ___________________________ bones. Nevertheless, with prolonged anemia, yellow marrow can convert to ________________________ marrow.
12.4.
Structure of Bone: Histology
a. Unlike the extracellular matrix of other connective tissues, the extracellular matrix ______________________, meaning that bone mineral crystals called ____________________ are deposited onto the surface of the collagen fibers. Mechanically speaking, the collagen fibers are good at resisting _____________________________ forces, while the bone mineral is good at resisting ________________________________ forces.
b. The four cell types present in bone tissue are the _______________________, _____________________, _____________________, and _______________. Of these the main secretory cell is the __________________________ which functions in bone formation while the ________________________ is the cell responsible for bone resorption.
c. Osteoblasts are derived from _______________________________ which are mitotically active cells. The main secretory product of osteoblasts is ______________________________ along with other non-collagen proteins. These cells lie on bone surfaces, usually on top of a layer of non-calcified bone matrix called ________________________.
d. The other cell which lies directly on bone surfaces is the _________________________, a cell which has _______________________ nuclei. These cells release __________________, which dissolves bone mineral and ______________________ which digest matrix proteins. The active osteoclast has a highly convoluted membrane facing bone called the ____________________________.
e. During bone growth, osteoblasts become trapped in bone matrix, forming _______________________. These cells sit in spaces called ____________ while their cell processes lie in spaces called _________________________.
f. On the outer surface of bone is found a structure called the _____________, which consists of two layers called the ___________________________ and ____________________________ layers. Of the two, the outer fibrous layer consists exclusively of ___________________, while the osteogenic layer has several cell types including __________________ and _________________, which lie on the bone surface and __________________ cells which lie superficial to these cells. In general osteoblasts which are active are __________________________________ in shape while inactive cells are ________________________________. Bone growth that takes place at the periosteum is _____________________________.
g. On the inner surface of bone facing the marrow cavity is a structure called the ______________________________. Unlike the periosteum, the endosteum has only a(n) __________________________ layer.
h. Bone tissue is organized into layers called ________________________. Just deep to the periosteum are lamellae which encircle the entire bone called ___________________________. Just deep to the endosteum are comparable structures called _____________________________.
i. ______________________ represent the results of bone remodeling, a process that involves first bone _____________________ followed by bone ________________________________. In the middle is a space called the _______________________ canal which contains a blood vessel and nerves. Surrounding these structure are a series of ____________________ lamellae. Blood vessels that lie in the middle of Harversian canals are derived from marrow vessels that send branches into bone matrix via __________________ canals.
j. ______________________ lamellae lie between Haversian systems.
12.5. Bone Formation
a. _______________________ refers to the process by which cells are recruited, matrix products are secreted, and the matrix______________________. There are two distinct types of ossification called ___________________________ and _______________________________ ossification. Any given bone will develop by _________________ of these methods but the final result of bone tissue will be the __________________________.
b. Most flat bones develop by _________________________ ossification, which involves the formation of a “________________________” due to the differentiation of mesenchymal cells. Just subjacent to this region, other mesenchymal cells differentiate into _______________________, which go on to form _______________________________ bone that is lined with a __________________. Meanwhile in the interior, _____________________ are formed which enlarge to form the ______________________ bone that makes up the middle of the future bone.
c. Unlike membranous bone formation, which occurs within _______________, endochondral ossification involves a ________________________ precursor. Most bones of the body develop via _______________________ ossification.
d. Within endochondral ossification, mesenchymal cells at the future site of bone formation first develop into ______________________. These cells begin to secrete matrix which surrounds them in spaces called ___________________, at which point they are referred to as ______________________. As a result of this process, a _________________________ cartilage model is created, surrounded by a _________________________.
e. The primary ossification center is established within the ________________ of the developing bone, in a process involving the destruction and removal of ___________________ and replacement with bone. During this process, blood vessels penetrate into the perichondrium turning it into a ________________________. By the time of birth a typical long bone consists of a ________________ diaphysis and ______________________ epiphyses.
f. Following birth, each epiphysis is converted to bone through the establishment of ______________________ ossification centers. Following this process, hyaline cartilage is left in the form of ____________________ cartilage on the articular surfaces and the ______________________ growth plate at the two ____________________________.
g. Growth in width takes place by ________________________ growth at the periosteum while the increase in length of a bone takes place through growth at the ________________________________.
h. The epiphyseal plate consists of regions called the zone of _______________; zone of ___________________; zone of _______________________; and the zone of ___________________. Of these cell division takes place in the zone of ______________________ and cartilage is replaced by bone in the zone of _________________________. No further growth in length is possible after _______________________ of the epiphyseal plate, leaving a bony landmark called the ________________________.
i. Of the factors that influence bone growth, the hormone __________________ stimulates insulin-like growth factors, which stimulate bone growth. Too much of this hormone produces a condition known as ___________________ while too little produces ________________________. The growth spurt of puberty results in part due to an increase in ________________________ and _________________________. In females, it is the ____________________ which are responsible for the characteristic differences in skeletal shape between males and females and for timing of the ultimate epiphyeal plate _______________________. Finally, another hormone called ______________________ is needed for normal calcification. Deficiencies of this hormone in children give rise to a condition known as ____________________, while _________________ is the condition when found in adults.
12.6. Joints
a. A joint, also called an _______________________ is a point of contact between two bones which can be classified structurally into three classes called ______________________ joints; _______________________ joints; and _________________________ joints. Of these, the _______________ joints possess a space between the two bones called the _________________ cavity.
b. Bones of the skull are connected by a type of fibrous joint called a _________________. Because this type of joint allows no movement, it is functionally classified as a ________________________.
c. A ______________ is a fibrous joint where there is more substantial amounts of connective tissue allowing some movement, and so this joint is functionally classified as an ___________________________.
d. Two types of cartilaginous joints are a ________________________ where the two bones are connected by hyaline cartilage; and a __________________ where the two bones are connected by fibrocartilage. An example of a synchondrosis is found at the _______________________ junctions where the ribs attach to the sternum. These joints are immovable, and are thus classified as _______________________. By contrast, the symphysis pubis allows some movement and thus is considered to be a ____________________ joint.
e. ______________________ joints offer the greatest range of motion and thus are considered to be __________________. They are enclosed by a connective tissue structure called the __________________________, which encloses the synovial cavity. This structure in turn consists of an outer layer, which forms the _____________________ capsule and an inner layer which forms the ______________________ membrane. Thickenings of the fibrous capsule form _______________________. The cells which secrete synovial fluid are found within the ____________________________.