Veterinary Technology Chapter 3 The Skeletal System

Objectives  Examine the skeletal system, and describe its functions.  Identify the components of bone, discuss the three cell types found in bones, and discuss how bones are classified.

Objectives  Differentiate between moveable and immoveable joints.  Discuss the chemical process in the formation of bones and calcification.  Identify and recall the names of bones found in livestock and companion animals.

Terms  calcification  carpals  cartilage  cartilaginous joints  diaphysis  endochondral  ossification  epiphysis  femur  fibrous joint  fibula  flat bones  humerus  joint  long bones  mandible  maxilla  metacarpals

Terms  metatarsus  osteoblasts  osteoclasts  osteocytes  osteoid  radius  red marrow  ribs  scapula  sesamoid bones  short bones  skeletal system  skull  synovial fluid  synovial joints  tarsus  tibia  ulna  vertebrae  yellow marrow

How many bones do humans have?  When you were born you had over 300 bones. As you grew, some of these bones began to fuse together. The result? An adult has only 206 bones!  You have over 230 moveable and semi-moveable joints in your body.  The human hand has 27 bones; your face has 14!  The longest bone in your body? Your thigh bone, the femur -- it's about 1/4 of your height.  The smallest is the stirrup bone in the ear which can measure 1/10 of an inch.

What is the skeletal system, and what are its functions?  In mammals the skeletal system consists of bones, teeth, joints, and structures that connect bones to other bones or muscles (e.g., ligaments, tendons, and cartilage).  The skeletal system gives animals shape and has the following functions.

What is the skeletal system, and what are its functions?  1. Support: Many bones of the body provide support, but this is especially true of the long bones. For example, the long bones in legs help support the trunk. Bones other than long bones also provide support. For example, the first vertebra supports the skull.

What is the skeletal system, and what are its functions?  2. Protection: A vital function of the skeletal system is the protection of vital internal organs. The skull protects the brain, and the rib cage protects the heart, lungs, and abdominal organs.

What is the skeletal system, and what are its functions?  3. Mineral storage: The outer layers of bony tissues are used for the storage of minerals (primarily calcium and phosphorus). Deposits and withdrawals of mineral ions from bone are continuous, which helps to maintain blood levels of calcium and phosphorus.

What is the skeletal system, and what are its functions?  4. Blood-cell formation: The inner core of bone is a soft tissue called bone marrow. Bone marrow is made in this hollow center called the medullary cavity. Red marrow is a major site of blood cell and platelet formation.  5. Energy storage: Yellow marrow is found in the shaft of long bones and other mature bones. Yellow marrow consists mostly of fat and serves as an energy reserve.

Bone Structure  C. Bones are classified by shape:  1. Long bones are cylindrical in shape and consist of a shaft with two ends. Found in limbs, long bones typically support body weight and act as levers. The femur, or thighbone, is an example of a long bone.

Bone Structure  2. Short bones are cube-like in that they are nearly equal in length and width. Short bones are found in the knee and hock and help to absorb the shock of impact and make up the fingers and toes.

Bone Structure  3. Flat bones are typically thinner and usually curved. Flat bones (e.g., ribs, scapula, and some bones in the skull) surround and protect vital organs.

What are bone components? What are the three cell types found in bones? How are bones classified  4. Sesamoid bones are small and embedded in tendons. The patella (knee cap) is the only human sesamoid bone.  5. Irregular bones have a variety of shapes and sizes. Vertebrae and some bones in the skull are examples of irregular bones.

Bone Structure  Bones grow in length but they also grow in thickness through a process called appositional growth. Growth in length occurs in long bones at the ends between the epiphysis and diaphysis. Long bones have two epiphysis (enlarged ends) and one diaphysis (shank).

Bone Structure of a Long Bone -page 30  Outer shell composed of dense (compact) bone.  Underneath, the spongy (cancellous) bone Where is it found? Read 2 nd paragraph!  Medullary Cavity = hollow center of the diaphysis (shaft).  Periosteum = thin layer of connective tissue. Blends into tendons and ligaments, binding them to the bone

Bone Structure of a Long Bone -page 30  A dried bone is composed of about 70% inorganic minerals, and 30% organic compounds. Calcium and phosphorus 

Bone Structure of a Long Bone  There are 3 types of bone cells: Osteoblasts: lay down the collagen matrix, become enclosed in the matrix and develop into osteocytes… Osteocytes: responsible for maintaining the bone matrix Osteoclasts: large cells that release the minerals from the bone.

Bone Structure of a Long Bone Disease conditions of bones? Bone is composed of a collection of microscopic units called osteons.  Center = canal  In canal = blood vessels, nerves

Joints and Movement  A joint, or articulation, is the union of bone or cartilage.  The classification of joints is based on joint structure and mobility.  3 types of joints

Joints and Movement  A. Fibrous joints include those united by connective tissue or fused bone. Fibrous joints, or fixed joints, typically do not permit any type of movement. An example of this type of joint is found in the skull.

What is the difference between a moveable and an immoveable joint?  B. Cartilage joints allow only slight movement; these are joints in which the bones are connected with cartilage. An example of a cartilaginous joint is the area between vertebrae. This area has a pad of cartilage that separates and cushions vertebrae. Growth plate in young animals

Joints and Movement  C. Synovial joints are freely movable joints in which the bones are held together (at the joints) by ligaments.  Within the joint is synovial fluid, which lubricates the joint and permits it to move freely and without friction.  Types of synovial joints include ball-and-socket, hinge, and pivot.

Joints and Movement  1. Ball-and-socket joints allow movement in all directions. For example, the ball of the femur fits into the socket on the hip bone.  2. A hinge joint allows movement in one axis. The knee and elbow joints are examples of hinge joints.

Joints and Movement  3. A pivot joint is found between the first and second vertebrae. It allows the head to be turned in more than one direction. A pivot joint allows rotation around a point.

Joints and Movement Several terms are used to describe the motion within a joint: - Flexion: the angle b/t the two bones gets smaller - Extension: the angle b/t the two bones increases - Abduction: when a part is moved away from the body - Adduction: when a part is moved closer to the body

Axial vs. Appendicular Skeletons  Skeleton can be divided into two main sections:  1.axial skeleton: contains skull, vertebrae, ribs and sternum  2.appendicular skeleton: contains bones of the limbs The total number of bones in the APP varies b/t species “Typical” dog has 320 total bones.  Length of tail?  With or without dewclaw? (first digit) Horses have a total of 205 bones 

Axial Skeletons  The bone that surrounds and protects the brain is known as the skull (cranium). Composed of numerous flat bones Shape based on species  The two bones that make up the jaw are known as the mandible and maxilla. Mandible = lower Maxilla = upper

Axial Skeletons  Similarly, bones that surround and protect the spinal cord are known as vertebrae.  Read page 34 first 3 paragraphs The column is broken down into divisions, beginning and the head and moving to the tail.  1. atlas=first vertebrae; up and down motion of head  2. axis=second vertebra; back and fourth motion Thoracic = attached to ribs, joint to sternum Lumbar=lower back Sacrum= group of 3 fused sacral vertebrae, joints to the pelvis Caudal (coccygeal) = tail  This number may greatly vary due to species

Appendicular Skeletons  The number and size of bones in the APP has many differences. A dog has 4 or 5 toes, a horse only has 1  High-Rise Syndrome = cats Great flexibility in scapula, fall a great distance = lower jaw hits ground to absorb shock.

Appendicular Skeleton  The shoulder blade is called the scapula.  In the front arm of an animal, the large single bone above the joint is called the humerus.  Below the joint contains two bones: the ulna(smaller) and the radius(heavy bone.  The front foot bones are known as the carpals and metacarpals, while the rear foot bones are known as the tarsus and metatarsus.  The rear leg of the animal has a structure similar to the front leg.  The large, single leg bone is called the femur, and the two smaller leg bones below the knee joint are the tibia(heavy bone) and fibula(smaller).

Appendicular Skeleton  The pelvis is made of two halves, then each half then is divided into a region: Ilium Ischium pubis

Bone Growth and Remondeling  Ossification: cartilage is replaced by bone tissue. Happens as the growth plate in young animals grows. For proper development, the rate of limb growth must match! Bassett Hounds = premature closing of distal growth plate in the ulna Subluxates = partially dislocate

Bone Growth and Remodeling  Radiographs (the actual picture) are produced when a stream of x-rays are passed through a body part. Dense structures allow a small amount of x- rays to pass through and show up as light on a radiograph. Lead prevents x-rays  The 5 stages of density: (least to most) 1. air (lungs) = darkest 2. fat (adipose) 3. soft tissue or muscle 4. bone 5. mineral = lightest or white on a radiograph

Relation of Bones, Muscles and Movement  Muscles are included in this chapter b/c the work with bones to allow animals to move.  Muscles are described by the point of their attachment: Origin: the fixed attachment point(more distal) Insertion: the moveable point(  They are also described based on their type of motion they cause: Extensors: cause bone to move into straighter alignment or open the joint Flexors: bend the joint(close the angle)

Relation of Bones, Muscles and Movement  Muscles are included in this chapter b/c the work with bones to allow animals to move.  Muscles are described by the point of their attachment: Origin: the fixed attachment point(more distal) Insertion: the moveable point(  They are also described based on their type of motion they cause: Extensors: cause bone to move into straighter alignment or open the joint Flexors: bend the joint(close the angle)

Clinical Practice  Fractures: occur when the physical force exerted on the bone is stronger than the bone itself. are common; the average person has two during a lifetime. Your risk of fracture depends, in part, on your age.

Clinical Practice  Simple Fracture: bone is broken into two, clean pieces.  Comminuted Fracture: results in many fragments of bone.  Compound (open) Fracture: when one of the ends of the bone ends punctures thought the skin.

Clinical Practice  In order for a fracture to heal, the bone ends must be put back in alignment and held without movement. Bone plate Intramedullary pin

Clinical Practice  Hip Dysplasia: the ball and socket joint of the hip becomes diseased. Socket becomes shallow More common in large dogs Genetics ?? Nutrition ??  Degenerative Joint Disease: cartilage lining becomes worn down. Pain, lameness, have trouble getting around

Review  What is the skeletal system, and what are its functions?  What are bone components? What are the three cell types found in bones? How are bones classified?  What is the difference between a moveable and an immoveable joint?

Review  What is the chemical process in the formation of bones and calcification?  What are the names of bones commonly found in livestock and companion animals?