Bones

Objectives
1. Identify the axial and appendicular subdivisions of the skeleton 2. Describe the functions of the skeletal system 3. Identify and classify different types of bones 4. Distinguish between osteoblast, osteoclast, and osteocyte function and describe the mechanism of bone remodeling 5. Relate the structure of long bone to its function 6. Identify and describe various types of bone fractures 7. Describe the stages of bone healing 8. Explain the differences between the male and female pelvis

Link to video about bone strength: []

Bone Song []

Website of Skeletal System: []

__** 1. Identify the axial and appendicular subdivisions of the skeleton **__  **Axial Skeleton (green) and Appendicular Skeleton (purple)** The **axial skeleton** consists of 80 bones throughout the head and trunk of the human body which form the center axis of the body. The five main parts of the axial skeleton include:
 * Bones of the skull
 * The vertebral column
 * The thoracic cage (This includes the sternum and ribs.)
 * The hyoid bone (a U-shaped bone that and hangs below the skull, suspended by ligaments. The hyoid serves as a base for muscles within the tongue and larynx.)
 * The ossicles (The three small bones in the middle ear. The ossicle bones help carry sound from the eardrum to the inner ear.)

The **appendicular skeleton** consists of 126 bones throughout the body which make motion possible and protects the organs of digestion, excretion, and reproduction. The eight main parts of the appendicular skeleton include: Arms Forearms The pelvic girdle (This includes the two hip bones. The pelvic girdle supports the weight of the body from the vertebral column; it also protects and supports the lower organs.) Thighs Legs
 * The shoulder girdle (This includes the clavicle and scapula. The shoulder girdle is a set of bones which connect the upper limbs, like the arms, forearms, and hands, to the axial skeleton on each side.)
 * Hands
 * Feet

[]
 * __Cervical Spine Anatomy__**

= = =__**2. Describe the functions of the skeletal system**__= There are 5 functions of the skeletal system 1. **Protection:** Protection for soft body organs like lungs and heart, as well as protection for the spinal cord and brain. Ex. sternum, cranium (fused skulls provides snug enclosement of the brain), vertebrae, rib cage (protects vital organs of the thorax), pelvis, etc. 2. **Support:** Framework for the body. The skeletal system gives the body its shape and structure.
 * They form the internal framework that supports and anchors all soft organs.
 * Rib cage supports the thoracic wall
 * Bones of the leg acts as pillars to support the body

Ex. femur, tibia, vertebrae, etc. 3. **Movement:** Pulls bones towards each other. The bones are used as levers to create movement, whether its a hinge, ball-in-socket, or saddle joint. Ex. humerus and ulna, femur and pelvis, philanges, etc. 4. **Storage:** Calcium, phosphorous salts, and lipids are stored in the [|Medullary Cavity] of bone. Ex. vertebrae, femur 5. **Blood Cell Production:** Red blood cells are produced in the marrow of the bone (hematopoiesis). Ex. body of vertebrae


 * __ 3. Identify and classify different types of bones __**

The adult skeleton is made of 206 bones. There are two basic types of osseous (bone) tissue which make up compact and some spongy bone. There are also hybrid variations such as spongy bone sandwich, which is a combination of both.
 * Compact Bone:** is composed of strong cylinders called Haversian systems or osteons, which contains lots of ECM (storage of Ca and P), is very dense, and appears smooth.
 * Spongy Bone:** is a lightweight bone that consists of an interwoven network of trabeculae. Spongy bone is composed of small needle-like pieces of bone and lots of open space.
 * Spongy Bone Sandwich:** can be found in flat bones, (Ex. The skull), and can be found in places that need to be very strong but also very light.

Bones come in many sizes and shapes. The unique shape of each bone fulfills a particular need and they are classified according to shape into four groups... Composed of a shaft with heads at both ends. Are mostly compact bone (the head is composed mostly of spongy bone and the shaft is compact bone). All bones of the limbs except wrist and ankle bones. || Cube-shaped. Mostly spongy bone. Ex. ankle and wrist bones. Sesamoid bones are a special type of short bone. They form within tendons. Ex. patella. || Thin, flattened, usually curved. Two thin layers of compact bone sandwiching a layer of spongy bone between them. Ex. most of the bones of skull, ribs, and sternum. || Bones that do not fit into the other categories. Ex. vertebrae and hip bone. || Link to bone structure video (compact, spongy, etc) [] =**__4. Distinguish between osteoblast, osteoclast and osteocyte function and describe the mechanism of bone remodeling__**=
 * Classifications of Bones**
 * ** Long bones ** || ** Short bones ** || ** Flat Bones ** || ** Irregular bones ** ||
 * Longer than they are wide.


 *  || **Function ** || **How it Helps with Bone Remodeling ** ||
 * **Osteoblast ** || Osteoblasts are small bone cells which synthesize and secrete EMC (composed of calcium, phosphorus and collagen fibers.) || When a bone is constantly being used it needs to become stronger in order to support bone. Osteoblasts, located in the periosteum (the nutrient sheath of the bone) it helps to increase bone mass ||
 * **Osteoclast ** || Osteoclasts work at the opposite end of homeostasis of calcium levels, because when activated by the parathyroid hormone osteoclasts release calcium back into the blood taking it away from the bone. || When a bone is not being used the bone is remodeled so it smaller, since the extra strength is not needed. Osteroclast breaks down the ECM of the bone (this is known as bone resorption.) ||
 * **Osteocyte ** || Osteocytes are the most common cells found in the human bone. They are mature bone cells which keep the bone metabolically active. || Osteocytes are created by osteoblasts and are found in clusters known as osteons. Osteocytes are connected by cannaliculi, which help transfer materials such as minerals and waste <span style="font-size: 9pt; vertical-align: baseline; font-family: 'Arial','sans-serif';"> ||



[|Bone Remodeling Video] [|Link to website with animations of bone remodeling and bone growth]


 * __ 5. Relate the structure of long bone to its function __**

Long bones have an epiphysis, or head, on each end of the shaft. These consist of spongy bone and are surrounded by a thin layer of compact bone. Since spongy bone weighs less than compact bone, it makes it easier to move. Even though the spongy bone is lighter, it is still able to provide a lot of support since it has many small beams, called trabeculae, distributed throughout it. These trabeculae contain a strong ECM which is essential for the bone.The shape of the epiphysis, with its articular cartilage that has a smooth and slippery texture, facilitates movement, articulation with other bones, and muscle and ligament attachment. It also acts as cushioning so that the bones do not grind against each other, and this provides protection from the bones wearing down. Significantly, articular cartilage is also avascular so that you will not bleed internally everytime you move and your bones rub against it. The diaphysis, commonly referred to as the shaft, is mostly made up of compact bone. There are long columns (the Haversian system) that together form a very strong bone. The ECM, extra cellular matrix, is contained in here and with it are collagen fibers, calcium, and phosphorous salts, making the bone very strong. This helps the body have a strong structural framework, as well as with protection. In the diaphysis, there is something known as the medullary cavity. This cavity contains red bone marrow, most common when we are young, and yellow bone marrow, most common when we are old. Blood cells are made in the bone marrow, which means that this cavity allows blood cell production (hematoesis) to take place which is needed by the skeletal system. The yellow bone marrow, which is fatty connective tissue, stores lipids, and it is for this reason the long bone performs the function of storage. The ECM in the bone also works as a storage center since it stores calcium and phosphorous salts. = = =**__6. Identify and describe the various types of bone fractures__**=
 * Closed (simple) fracture:** bone breaks cleanly but does not penetrate the skin.
 * Open (compound) fracture:** broken bones ends penetrate through the skin.


 * =Fracture Type= || ** Description ** || ** Comment ** ||
 * ** Comminuted ** || Bone breaks into many fragments. || Particularly common in the aged, whose bones are more brittle. ||
 * ** Compression ** || Bone is crushed (ex. osteoporotic bones) || Common in porous bones ||
 * ** Depressed ** || Broken bone portion is pressed inward. || Typical of skull fracture ||
 * ** Impacted ** || Broken bone ends are forced into each other. || Commonly occurs when one attempts to break a fall with outstretched arms. ||
 * ** Spiral ** || Ragged break occurs when excessive twisting forces are applied to a bone. || Common sports fracture. ||
 * ** Greenstick ** || Bone breaks incompletely, much in the way a green twig breaks. || Common in children, whose bones are more flexible than those of adults ||

**Complex fractures**
In long bones, such as the thighbone (femur) an injury is more likely to cause a more complex, spiral fracture. This leaves surfaces that are less likely to re-unite easily.

**Stress fractures**
Bones can break due to small repeated stresses and strains. This is known as a stress or fatigue fracture, and is most often seen in the lower leg or foot bones of athletes.

**Avulsion fractures**
Muscle or ligament that supports or is attached to bone can also cause a fracture called an avulsion fracture. This happens when the ligament or muscle pulls on the bone causing it to fracture.

**Hairline fractures**
Hairline fractures may occur after a trip or a fall. The bone is only partially fractured. They can be difficult to detect.

**Depressed fractures**
A depressed fracture is when part of the bone is pushed out of line with the rest of the bone. This is usually in the skull.

**Pathological fractures**
If a tumour or other disease causing factor is weakening the bone, it's called a pathological fracture.

**Complicated fractures**
A fracture is described as complicated if there is damage to major structures near the fractured bone, such as an artery.

**Compound fractures**
The broken end of a bone can break the skin, or protrude through the skin. This is known as an open or compound fracture and it can lead to infection and blood loss.

**Closed fractures**
If the bone doesn't damage the skin it's called a closed fracture.

**Comminuted fractures**
Sometimes, particularly in more serious accidents, the bone can fracture in a way that produces several fragments. This is called a comminuted fracture.

**Impacted fractures**
After a fracture, the broken fragments of bone usually separate to some degree. Sometimes one fragment of bone is driven into another. This is called an impacted fracture.

Fragility fractures
From middle-age onwards, your bones lose density and fractures are more likely. Osteoporosis is a bone disease that speeds up this process and weakens the bones. This makes people with osteoporosis more likely to have fragility fractures, which can occur after a minor fall, such as falling from standing height or less. For further information see Related topics.

Broken bones in children
Fractures in children tend to be different to those in adults because bone is softer and more able to bend. When fractures occur, the bone is not always broken completely. The bone can buckle and split and result in what is known as a greenstick fracture. Another type of fracture common in children is a growth plate fracture, called an epiphyseal plate fracture. Bone grows in length from the growth plates near the ends of long bones. These fractures can affect bone growth.


 * Animation about common fractures**
 * []**

The severity of a fracture depends upon its location and the damage done to the bone and tissue near it. Serious fractures can have dangerous complications if not treated promptly; possible complications include damage to blood vessels or nerves and infection of the bone ( [|osteomyelitis]) or surrounding tissue. Recuperation time varies depending on the age and health of the patient and the type of fracture. A minor fracture in a child may heal within a few weeks; a serious fracture in an older person may take months to heal.



Types of Fractures Video- []



=**__7. Describe the stages of bone healing__**=

Inorder for a bone to heal **reduction** (realignment of bone ends) must occur. There are two types of reduction... After the broken bone is reduced, it is immobilized by a cast or traction to allow the followinghealing process to begin...
 * Closed Reduction-** the bone ends are coaxed back into their normal position by the physician's hands
 * Open Reduction-** surgery is performed and the bone ends are secured together with pins and wires

Phases of fracture healing There are three major phases of fracture healing, two of which can be further sub-divided to make a total of five phases;
 * 1. **Reactive Phase**
 * i. Fracture and inflammatory phase
 * ii. Granulation tissue formation
 * 2. **Reparative Phase**
 * iii. Callus formation
 * iv. Lamellar bone deposition
 * 3. **Remodeling Phase**
 * v. Remodeling to original bone contour

When a person fractures a bone, there are several steps and procedures that are implemented so that the healing process is quick and efficient. Once the fracture occurs, blood cells begin to rush to the site of the fracture. The cells then clot, causing a hematoma. Furthermore, the tissue cells around the clot begin to die off. Next, chrondroblasts rush to the area to create cartilage, which serves as the basis for the bone to be formed. Then, osteoblasts release an ECM containing calcium and phosphorus. Finally, once the healing process is finished, the osteoblasts turn into mature osteoclasts. Despite their remarkable strength, bones are susceptible to fractures or breaks. During youth, most fractures result from exceptional trauma that twists or smashes the bones. In old age, most fractures occur as bones thin and weaken. A fracture is treated by reduction, the realignment of the broken bone ends. In closed reduction, the bone ends are coaxed into position by the physician's hands. In open reduction, the bone ends are secured together surgically with pins or wires. For a simple fracture the healing time is six to eight weeks for small or medium-sized bones in young adults, but it is much longer for large, weight-bearing bones and for bones of elderly people because of their poorer circulation. Repair in a simple fracture involves four major stages:

1. **__Hematoma formation:__** When a bone breaks, **//blood vessels//** in the bone and periosteum are torn and hemorrhage. As a result, a **//hematoma//**, a mass of clotted blood, forms at the fracture sight. Soon, **//bone cells//** deprived of nutrition **//die//** and the tissue at the site becomes swollen and painful and inflamed.

2. **__Fibrocartilaginous callus formation__.** Within a few days, several events lead to the formation of __//**soft granulation**//__ tissue. **//Capillaries//** grow into the hematoma and **//phagocytic//** cells invade the area and begin cleaning up the debris. Meanwhile, **//fibroblasts//** (and osteoblasts) invade the fracture site from the nearby periosteum and endosteum and begin reconstructing the bone. The fibroblasts produce **//collagen fibers//** that span the break and connect the broken bone ends and some differentiate into chondroblasts that secrete **//cartilage matrix//**. This entire mass of repair tissue, now called **//fibrocartilaginous callus//**, splints the broken bone.

3. **__Bony callus formation__.** Within a week, **//osteoblasts//** begin forming spongy bone and new bone **//trabeculae//** begin to appear in the fibrocartilaginous callus and gradually convert it to a **//bony or hard callus//** of spongy bone. Bony callus formation continues until a firm union is formed about two months later.


 * 4. __Bone Remodeling__.** Beginning during bony callus formation and continuing for several months after, the bony callus is **//remodeled//**. The excess material on the diaphysis exterior and within the medullary cavity is removed, and compact bone is laid down to reconstruct the shaft walls. The final structure of the remodeled area resembles that of the original unbroken bony region because it responds to the same set of mechanical stressors.

Slideshow: Components of Bone Healing - []



A Video of Bone Repair - media type="youtube" key="qVougiCEgH8" height="344" width="425"

=**__8. Explain the differences between the male and female pelvis__**= <span style="font-family: 'Times New Roman', Times, serif;">Document used in class - [|Pelvis differences.doc] <span style="font-family: 'Times New Roman', Times, serif;">The pelvis is a basin-shaped structure that supports the spinal column and protects the abdominal organs. It contains the following:


 * <span style="font-family: 'Times New Roman', Times, serif;">sacrum - a spade-shaped bone that is formed by the fusion of five originally separate sacral vertebrae.
 * <span style="font-family: 'Times New Roman', Times, serif;">coccyx ( tail bone.) - formed by the fusion of four originally separated coccygeal bones.
 * <span style="font-family: 'Times New Roman', Times, serif;">three hip bones, including the following:
 * <span style="font-family: 'Times New Roman', Times, serif;">ilium - the broad, flaring portion of the hip bone (the crest of the pelvis).
 * <span style="font-family: 'Times New Roman', Times, serif;">pubis - the lower, posterior part of the hip bone.
 * <span style="font-family: 'Times New Roman', Times, serif;">ischium - one of the bones that helps form the hip.

<span style="font-family: 'Times New Roman', Times, serif;"><span style="font-family: Arial, Helvetica, sans-serif;"><span style="font-family: 'Times New Roman', Times, serif;">-A male pelvis has a pelvic girdle optimised for walking/running. -A female pelvis has a wider pelvic opening to assist childbirth. - The female pelvis …. · The bones are more delicate – thin and light <span style="font-family: 'Times New Roman', Times, serif;">· The pelvis is less massive <span style="font-family: 'Times New Roman', Times, serif;">· The pelvis is more shallow <span style="font-family: 'Times New Roman', Times, serif;">· The ilia are less sloped <span style="font-family: 'Times New Roman', Times, serif;">· The anterior iliac spines are more widely separated – thus the greater prominence of the hips laterally <span style="font-family: 'Times New Roman', Times, serif;">· The superior aperture of the lesser pelvis (pelvic inlet) is larger, more nearly circular and has greater obliquity <span style="font-family: 'Times New Roman', Times, serif;">· The cavity of the pelvis is shallower and wider <span style="font-family: 'Times New Roman', Times, serif;">· Sacrum is shorter, wider and the upper part is less curved, so the sacral promontory is less imposing into the pelvic cavity <span style="font-family: 'Times New Roman', Times, serif;">· The obturator foramina are triangular – oval in shape and smaller in size than the male circular foramina <span style="font-family: 'Times New Roman', Times, serif;">· The inferior aperture of the lesser pelvis (pelvic outlet) is larger and the coccyx is more moveable <span style="font-family: 'Times New Roman', Times, serif;">· The sciatic notches are wider and shallower <span style="font-family: 'Times New Roman', Times, serif;">· The spines of the ischia project less inward – hence not protruding as much into the pelvic cavity <span style="font-family: 'Times New Roman', Times, serif;">· The acetabula are smaller and look more distinctly forward <span style="font-family: 'Times New Roman', Times, serif;">· The superior pubic ramus is longer than the width of the acetabulum <span style="font-family: 'Times New Roman', Times, serif;">· Ischial tuberosities and the acetabula are more wider apart <span style="font-family: 'Times New Roman', Times, serif;">· The pubic symphysis is less deep <span style="font-family: 'Times New Roman', Times, serif;">· The muscle attachments are more poorly marked <span style="font-family: 'Times New Roman', Times, serif;">· The pubic arch is wider an more rounded than in the male where it is an angle rather than an arch. (~ 90 o c.f ~ 60o) The pelvis is divided by an oblique line passing through the prominence of the sacrum, the arcuate and pectineal lines, and the upper margin of the pubic symphysis, into the greater and lesser pelvis. The greater pelvis is: <span style="font-family: 'Times New Roman', Times, serif;">· Superior to the pelvic inlet <span style="font-family: 'Times New Roman', Times, serif;">· Bounded by the abdominal wall anteriorly, the iliac fossae posterolaterally and the L5 and S1 vertebrae posteriorly <span style="font-family: 'Times New Roman', Times, serif;">· The location of some of the abdominal viscera like the sigmoid colon and ileum <span style="font-family: 'Times New Roman', Times, serif;">· It supports the intestines and transmits some of their weight to the anterior wall of the abdomen. The lesser pelvis is: <span style="font-family: 'Times New Roman', Times, serif;">· Between the pelvic inlet and outlet <span style="font-family: 'Times New Roman', Times, serif;">· Known as the true pelvic cavity <span style="font-family: 'Times New Roman', Times, serif;">· Bounded by the pelvic surfaces of the hip bones, sacrum and coccyx <span style="font-family: 'Times New Roman', Times, serif;">· Limited inferiorly by the musculofascial pelvic diaphragm <span style="font-family: 'Times New Roman', Times, serif;">· The location of the pelvic viscera – the urinary bladder and reproductive organs such as the uterus and ovaries

Pelvic inlet <span style="font-family: 'Times New Roman', Times, serif;">The size and shape of the pelvic inlet is important because it is through this opening that the fetal head enters the lesser pelvis during labour. The size of the lesser pelvis is particularly important in obstetrics because it is the bony pelvic canal through which the fetus passes during vaginal birth. To determine the capacity of the female pelvis for childbearing, the diameters of the lesser pelvis are noted radiologically or during a pelvic examination. The pelvic inlet is variable in contour. The shape can be affected by sexual, racial and nutritional differences in the population. It is heart shaped in males and some females, although in most females the opening is larger and is more rounded or oval in contour. The periphery of the pelvic inlet is formed by the pelvic brim which is indicated by the linea terminalis. This is an oblique ridge on the internal surface of the ilium (also known as the arcuate line) and is continued onto the superior pubic ramus as the pectineal line. The inlet is completed anteriorly by the pubic crests and posteriorly by the anterior margin of the base of the sacrum and the sacrovertebral angle (sacral promontory). The inlet has three principal diameters which can be measured: <span style="font-family: 'Times New Roman', Times, serif;">· The anteroposterior. Extends from the sacral promontory to the pubic symphysis and is measured on average about 110mm in the female <span style="font-family: 'Times New Roman', Times, serif;">· The transverse diameter. Extends across the width from the midpoint of the pelvic brim on one side to the other on the opposite side. About 135mm on average in females <span style="font-family: 'Times New Roman', Times, serif;">· Oblique diameter. From the iliopectineal eminence on one side to the sacroiliac articulation on the opposite. Average measurement is 125mm in female <span style="font-family: 'Times New Roman', Times, serif;">Pelvic outlet <span style="font-family: 'Times New Roman', Times, serif;">The pelvic outlet has a more irregular contour. It is bounded posteriorly by the point of the coccyx, and laterally by the ischial tuberosities. These eminences are separated by three notches: one in front, the pubic arch, formed by the convergence of the inferior rami of the ischium and pubis on either side. The other notches, one on either side, are formed by the sacrum and coccyx behind, the ischium in front, and the ilium above; they are called the sciatic notches; in the natural state they are converted into foramina by the sacrotuberous and sacrospinous ligaments. When the ligaments are // in // situ, the inferior aperture of the pelvis is lozenge-shaped or diamond shaped, bounded, in front, by the pubic arcuate ligament and the inferior rami of the pubes and ischia; laterally, by the ischial tuberosities; and behind, by the sacrotuberous ligaments and the tip of the coccyx. There are two diameters of the pelvic outlet: <span style="font-family: 'Times New Roman', Times, serif;">· Anteroposterior diameter. Extends from the tip of the coccyx to the lower part of the pubic symphysis. In the female average diameter is 90 – 115mm. It varies with the length of the coccyx, and is capable of increase or diminution, on account of the mobility of the coccyx. <span style="font-family: 'Times New Roman', Times, serif;">· Transverse diameter. Measured between the posterior parts of the ischial tuberosities about 115mm in the female. Types of pelvis <span style="font-family: 'Times New Roman', Times, serif;">There are four main types of pelvis, the prevalence dependent on sex and race. For example the relative frequencies in white females is: <span style="font-family: 'Times New Roman', Times, serif;">· Gynaecoid – round with enlarged transverse diameter – normal female type – 41.4% <span style="font-family: 'Times New Roman', Times, serif;"><span style="font-family: Arial, Helvetica, sans-serif;">· <span style="font-family: 'Times New Roman', Times, serif;"><span style="font-family: 'Times New Roman', Times, serif;">Of major obstetrical and gynaecological significance Android – heart shaped – in a woman may present hazards to normal delivery of a baby – 32.5% <span style="font-family: Arial, Helvetica, sans-serif;"><span style="font-family: 'Times New Roman', Times, serif;">· Anthropoid – long AP diameter – 23.5% · Platypelloid – long transverse diameter – 2.6% <span style="font-family: Arial, Helvetica, sans-serif;">· <span style="font-family: 'Times New Roman', Times, serif;"> **Ways to tell [|male] pelvis from [|female]:** > FEMALE-- more flared and cradle-like with anterior iliac spines farther apart > <span style="color: rgb(42,16,244);">MALE--more straight or “up-and-down” in shape > FEMALE-- smaller and triangular in female > <span style="color: rgb(89,34,236);">MALE-- larger and rounded in shape > <span style="color: rgb(231,91,241);">FEMALE-- greater than 90° (obtuse angle) and more rounded > <span style="color: rgb(55,34,226);">MALE-- less than 90° (acute angle) and more sharply angled<span style="color: rgb(71,33,228);"> > FEMALE --larger--big enough for head of baby to pass through >>>> <span style="color: rgb(229,60,236);">FEMALE-- it is straighter and has a movable joint. Can sometimes be pointed in and the mother will have to have a c-section in order to accomodate the baby. >>>> <span style="color: rgb(55,34,226);">MALE-- turned forwards<span style="color: rgb(55,34,226);"> and as a rule firmly joined to the sacrum.
 * 1) **Spread of ilium:**<span style="color: rgb(255,0,251);">
 * 1) **Shape of hole in ischium:** <span style="color: rgb(229,58,248);">
 * 1) **Angle across pubic symphysis = pubic arch:**
 * 1) **Inner diameter and distance between ischia:** <span style="color: rgb(218,51,225);">
 * 1) **The coccyx:**

Left: Modern Female Pelvis Right: Modern Male Pelvis