Skeletal and Muscular Systems Module 2 PDF

**MODULE 2** **Intended Learning Outcomes (ILO)** At the end of this module, you will be able to: 1\. Classify bones according to gross appearance 2\. Describe the functions of bones 3\. Classify muscles according to locations 4\. Describe the functions of muscles **Content Focus** **The Ske...

**MODULE 2** **Intended Learning Outcomes (ILO)** At the end of this module, you will be able to: 1\. Classify bones according to gross appearance 2\. Describe the functions of bones 3\. Classify muscles according to locations 4\. Describe the functions of muscles **Content Focus** **The Skeletal System** In this module you will study the basics of **anatomy** and **physiology** of the bones and meat of domestic animals. You will identify the different structures of the bones and muscles in the body. The skeletal system serves as the framework where the muscles are attached into. It's the skeletal system that determines the degree of muscling that the animal may have. The bigger the framework, the bigger the body of the animal is. The skeletal system is made up of bones and cartilages. True bones are formed by **oosification**. There are more bones in younger animals than in mature animals due to fusion of some bones as the animal gets older. Long bones continue to grow as the animal grows, with oosification of the cartilages in its epiphysis. The bones of the animals are arranged along the midline/axis (**axial skeleton**) and in the extremities/appendages (**appendicular skeleton**). The pictures used in this module are combinations of animal and human bone structures. Human bone images are used to emphasize the specific locations of the bones, and to facilitate easy learning. **Functions of Bones** 1\. Provides the basis of the external structure and appearance of an animal (framework). 2\. Protects the vital organs of the body nervous system - skull and vertebral column heart and lungs - rib cage urogenital system - pelvis 3\. Acts as levers and supports the muscular activities for locomotion, defense, offense, grasping and others 4\. Serve as dynamic storage area for minerals (calcium and phosphorous) which are deposited and withdrawn as needed by the body. 5\. Provide a site for blood formation (blood cells are formed in the bone marrow) **Classification of Bones** **Long Bones** Long bones are greater in one dimension than any other. Each consists of a relatively cyclindrical shaft (the diaphysis) and two extremities (epiphyses) and metaphysis in between (Fig. 7). **Functions:** Serve as levers and aid in support, locomotion and prehension. **Examples:** Thoracic limbs - humerus, radius, ulna, metacarpals Pelvic limbs - femur, tibia, fibula, metatarsals **Short Bones** Short bones are cuboid or approximately equal in all dimensions. There is no single marrow cavity, but the interior is composed of spongy bone filled with marrow spaces. The exterior is formed by a thin layer of compact bone (Fig. 7). **Functions:** Absorb concussion **Examples:** carpus and tarsus (hock) **Flat Bones** Flat bones are relatively thin and expanded in two dimensions. They consist of two plates of compact bone, the lamina externa and lamina interna, separated by spongy material called diploë (Fig. 7). **Functions:** Protection of vital organs such as the brain (skull), the heart and lungs (scapula and ribs) and the pelvic viscera (pelvis) and attachment of muscles. **Sesamoid bones** Sesamoid bones are so called because of their fancied resemblance to a sesame seed (Fig. 7). **Functions:** To reduce friction, increase leverage, or change the direction of pull. **Example:** Patella (kneecap) **Pneumatic Bones** Pneumatic bones contain air spaces or sinuses that communicate with the atmosphere. **Examples:** Frontal bones and maxillary bones of the skull Avian bones **Irregular Bones** Irregular bones are unpaired bones on the median plane; they include the vertebrae and some of the unpaired bones of the skull. They feature prominent processes (Fig. 7). **Functions:** Protection, support and muscular attachment https://www.visiblebody.com/learn/skeleton/types-of-bones **Fig. 7.** Bone types **Composition of Bones** Bones are living tissues packed with living cells called **osteocytes**. Each osteocyte is housed in its own hole or lacuna and are clustered into **Harvesian system**. In some parts of each bone, there are special cells called **osteoblasts** which make new bone, while in other parts there are **osteoclasts**, that break down old bones. The outer covering of the bone is called **periosteum**. Beneath it is a compact bone where food and oxygen move along blood vessels in the Harvesian canals. Compact bone is reinforced by strong rods called **osteons**. The outer layer of the compact bone is hard and very strong, but the inner layer, the spongy bone is very light due to the presence of many thin structures called **traberculae**. The innermost is a cavity filled with a soft, jelly-like substance called bone marrow. In young animals, the bone marrow is color red, and it becomes yellowish as the animal gets older. The bones are made up of organic and inorganic matter: 1\. **Organic matter** - provides toughness, elasticity and resilience to the bone, but as the animal gets older, the bones become brittle and easily breaks or fractured. 2\. **Inorganic matter** - provides hardness and rigidity. If the bone is deficient in Ca and P, it becomes flexible. **Fig. 8.** Composition of bone **Other Structures Associated with Bones** **Ligaments** are connective tissues that connects bones to bones **Tendons** are connective tissues that connects muscles to bones **Axial Skeleton** The axial skeleton includes bones on or attached to the midline (axis) of the body and comprise the skull, vertebral column, sternum, and ribs. The appendicular skeleton is made up of the bones of the limbs. The bones of the thoracic limb are compared to those of the pelvic limb. The vertebral column is generally made up of vertebrae, an irregular bone which varies slightly in each of the five regions in the body. 1\. **Cervical vertebrae are in the neck region.** The first cervical vertebrae is called "atlas" and this facilitates the nodding movement of the head. The second vertebrae is called "axis" and this facilitates the horizontal movement of the head. 2\. **Thoracic vertebrae are in the chest region.** Cattle and horses have long dorsal processes where hump muscles are attached. 3\. **Lumbar vertebrae are found in the abdominal region.** In most animals, this have wide and flat horizontal transverse processes (protrusions) providing the space for muscles and accommodates riders at the back. 4\. **Sacral vertebrae are found in the pelvic or hip region.** It is a fused bone. 5\. **Coccygeal or caudal vertebrae are the bones forming the tail.** They vary in length from one animal to another. Its size becomes smaller caudally. In poultry, the lumbar and sacral vertebrae are fused, called lumbosacral vertebrae and the coccygeal vertebrae is very short, called the pygostyle. Table 6. Vertebral formula of domestic animals +-----------+-----------+-----------+-----------+-----------+-----------+ | **Animal* | **Cervica | **Thoraci | **Lumbar* | **Sacral* | **Caudal* | | * | l** | c** | * | * | * | +-----------+-----------+-----------+-----------+-----------+-----------+ | Man | 7 | 12 | 5 | 5 | 4 | | | | | | | | | Horse | 7 | 18 | 6 | 5 | 15-20 | | | | | | | | | Cattle | 7 | 13 | 6 | 5 | 18-20 | | | | | | | | | Sheep | 7 | 13 | 6 | 4 | 16-20 | | | | | | | | | Goat | 7 | 13 | 7 | 4 | 12 | | | | | | | | | Pig | 7 | 14-15 | 6 | 4 | 20-23 | | | | | | | | | Dog | 7 | 13 | 7 | 3 | 20-23 | | | | | | | | | Chicken | 14 | 7 | | | Pygostyle | | | | | | | 6 | +-----------+-----------+-----------+-----------+-----------+-----------+ | | | | Lumbosacr | | | | | | | al | | | | | | | 14 | | | +-----------+-----------+-----------+-----------+-----------+-----------+ **Appendicular Skeleton** The appendicular skeleton is composed of the bones of the fore and hind legs attached to the fused bones that form the shoulders and hips (pelvis). Table 7. The bones in the appendicular skeleton of an animal +-----------------------------------+-----------------------------------+ | **Pectoral girdle (shoulder | **Pelvic girdle (hip bone)** | | bone)** | | +-----------------------------------+-----------------------------------+ | Scapula (shoulder blade) | Ilium (pin bone) | | | | | Clavicle (collar bone or wishbone | Ischium | | in poultry) | | | | Publis (pelvis) | | Coracoid | | +-----------------------------------+-----------------------------------+ | **Pectoral limbs (fore limbs)** | **Pelvic limbs (hind limbs)** | +-----------------------------------+-----------------------------------+ | Humerus (arm) | Femur (thigh) | | | | | Radius and ulna (forearms) | Tibia and fibula (legs) | | | | | Carpus (wrist/knee) | Tarsus (hock) | | | | | Metacarpus (cannon bones) | Metatarsus (cannon bones) | | | | | Phalanges (digits) | Phalanges (digits) | +-----------------------------------+-----------------------------------+ In poultry, the pectoral girdle and limbs are modified into wings. Some bones are fused and become vestigial. Dewclaws are structures correspond to the thumb in humans which is found as the first digit in the dogs and cats and as the second and fifth digits in cattle, sheep and goats. The 3rd and 4th digits are the two principal toes in cattle, sheep and goats. This makes up the cloven-footed animals' toes. The 3rd digit is the principal digit used by horses.