Skeletal System PDF

# SKELETAL SYSTEM - Bone tissues makes up about 18% of the total human body weight. - The skeletal system supports and protects the body while giving it shape and form. - **Osteology:** It is the branch of science that deals with the study of the skeletal system, their structure and functions. ##...

# SKELETAL SYSTEM - Bone tissues makes up about 18% of the total human body weight. - The skeletal system supports and protects the body while giving it shape and form. - **Osteology:** It is the branch of science that deals with the study of the skeletal system, their structure and functions. ## COMPOSED OF: - Bones - Cartilage - Joints - Ligaments # FUNCTIONS OF SKELETAL SYSTEM - **SUPPORT:** Hard framework that supports and anchors the soft organs of the body. - **PROTECTION:** Surrounds organs such as the brain and spinal cord. - **MOVEMENT:** Allows for muscle attachment therefore the bones are used as levers. - **STORAGE:** Minerals and lipids are stored within bone material. - **BLOOD CELL FORMATION:** The bone marrow is responsible for blood cell production. # DIVISIONS OF THE SKELETAL SYSTEM The human skeleton consists of 206 named bones. Bones of the skeleton are grouped into two principal divisions: ## Axial Skeleton - Skull bones, auditory ossicles (ear bones), hyoid bone, ribs, sternum (breastbone), and bones of the vertebral column ## Appendicular skeleton - Consists of the bones of the upper and lower limbs (extremities), plus the bones forming the girdles that connect the limbs to the axial skeleton | DIVISION OF THE SKELETON | STRUCTURE | NUMBER OF BONES | |---|---|---| | **Axial Skeleton** | Skull | 22 | | | Cranium | 8 | | | Face | 14 | | | Auditory ossicles | 6 | | | Vertebral column | 26 | | | Sternum | 1 | | | Thorax | 24 | | | Ribs | 24 | | | Hyoid | 1 | | **Appendicular Skeleton** | Pectoral (shoulder) girdles | 2 | | | Clavicle | 2 | | | Scapula | 2 | | | Upper limbs | 32 | | | Humerus | 2 | | | Ulna | 2 | | | Radius | 2 | | | Carpals | 16 | | | Metacarpals | 10 | | | Phalanges | 28 | | | Pelvic (hip) girdle | 2 | | | Hip, pelvic, or coxal bone | 2 | | | Lower Limbs | 31 | | | Femur | 2 | | | Patella | | | | Fibula | 2 | | | Tibia | 2 | | | Tanals | 14 | | | Metatarsals | 10 | | | Phalanges | 28 | # CLASSIFICATION OF BONE BASED ON SHAPE - Bones can be classified into five types based on shape: - **Long:** Greater length than width and are slightly curved for strength - **Short:** Cube-shaped and are nearly equal in length and width - **Flat:** Thin and composed of two nearly parallel plates of compact bone tissue enclosing a layer of spongy bone tissue - **Irregular:** Complex shapes and cannot be grouped into any of the previous categories - **Sesamoid:** Protect tendons from excessive wear and tear # THE AXIAL SKELETON The axial skeleton consists of: 1. Skull. 2. Vertebral column (spinal column). 3. Thoracic cage. 4. Sternum. ## Skull - The skull is situated on the upper end of vertebral column and its bony structure is divided into 2 parts. - **The cranium** - **The face** ### Cranium - It is formed by flat and irregular bones that provides a bony protection to the brain. - **Frontal Bone** - It forms the forehead. - It forms parts of eye sockets. - The coronal suture joins the frontal and parietal bones. - **Parietal Bones** - It form the sides and roof of the cranial cavity. - It articulates with each other at the sagittal suture. - It joins the frontal bone with coronal suture and occipital bone with lambdoidal suture and the temporal bones at the squamous suture. - **Temporal Bones** - These bones lie one on each side of the head and form immovable joints with the parietal, occipital, sphenoid and zygomatic bones. - The temporal bone articulates with the mendible at the tempo-mandibular joint. - **Occipital Bone** - It forms back of head and most of the base of the skull. - It has immovable joints with the parietal, temporal and sphenoid bones. - **Sphenoid Bone** - It occupies the middle portion of base of skull and it articulates with the occipital, temporal, parietal and frontal bones. - **Ethmoid Bone** - It occupies the anterior part of base of the skull and helps to form the orbital cavity, the nasal septum and the lateral walls of the nasal cavity. - It is very delight bone containing many air sinuses that opens into the nasal cavity. ### The Face (Facial bones) - **Nasal Bones** - Form the bridge of the nose - **Maxillae** - Form the upper jawbone - Form most of the hard palate - Separates the nasal cavity from the oral cavity - **Zygomatic Bones** - commonly called cheekbones, form the prominences of the cheeks - **Lacrimal Bones** - Form a part of the medial wall of each orbit - **Palatine Bones** - Form the posterior portion of the hard palate - **Inferior Nasal Conchae** - Form a part of the inferior lateral wall of the nasal cavity - **Vomer** - Forms the inferior portion of the nasal septum - **Mandible** - Lower jawbone - The largest, strongest facial bone - The only movable skull bone - **Nasal Septum** - Divides the interior of the nasal cavity into right and left sides - "Broken nose," in most cases, refers to septal damage rather than the nasal bones themselves - **Orbits** - Eye socket - **Foramina** - Openings for blood vessels, nerves, or ligaments of the skull ## The Vertebral column - Also called the spine, backbone, or spinal column - **Functions to:** - Protect the spinal cord - Support the head - Serve as a point of attachment for the ribs, pelvic girdle, and musclés - The vertebral column is curved to varying degrees in different locations - Curves increase the column strength - Help maintain balance in the upright position - Absorb shocks during walking, and help protect the vertebrae from fracture - **Composed of a series of bones called vertebrae (Adult=26)** - 7 cervical are in the neck region - 12 thoracic are posterior to the thoracic cavity - 5 lumbar support the lower back - 1 sacrum consists of five fused sacral vertebrae - 1 coccyx consists of four fused coccygeal vertebrae **Intervertebral Discs:** - Found between the bodies of adjacent vertebrae - **Functions to:** - Form strong joints - Permit various movements of the vertebral column - Absorb vertical shock - **Vertebrae typically consist of:** - A Body (weight bearing) - A vertebral arch (surrounds the spinal cord) - Several processes (points of attachment for muscles) ## Thorax: (Thoracic cage) - Thoracic cage is formed by the: - Sternum - Ribs - Costal cartilages - Thoracic vertebrae - **Functions to:** - Enclose and protect the organs in the thoracic and abdominal cavities - Provide support for the bones of the upper limbs - Play a role in breathing - **Sternum** - "Breastbone" located in the center of the thoracic wall - Consists of the manubrium, body, xiphoid process - **Ribs** - Twelve pairs of ribs give structural support to the sides of the thoracic cavity - **Costal cartilages** - Costal cartilages contribute to the elasticity of the thoracic cage # THE APPENDICULAR SKELETON The appendicular skeleton is composed of the bones of the upper and lower limbs, as well as the pectoral and pelvic girdles that connect the limbs to the axial skeleton. ## The Upper Limb The upper limb, or arm, is comprised of the following bones: ### Shoulder Girdle - **Clavicle:** The clavicle, or collarbone, is a long, S-shaped bone that helps to connect the upper limb to the axial skeleton. - **Scapula:** The scapula, or shoulder blade, is a flat triangular bone that provides support for the shoulder joint. ### Arm - **Humerus:** The humerus is the long bone of the upper arm, and connects to the shoulder joint at its proximal end and the elbow joint at its distal end. ### Forearm - **Ulna:** The ulna is one of the two bones of the forearm. Its medial side runs parallel to the humerus and is slightly longer than the radius. - **Radius:** The radius is the lateral forearm bone located on the thumb side. The radius is smaller than the ulna and runs parallel to the humerus. ### Hand The hand is comprised of the following: - **Carpals:** The carpals (wrist bones) are eight small bones arranged in two rows. The carpal bones provide flexibility for the wrist and the hand. - **Metacarpals:** The metacarpals are the five long bones of the palm. They are numbered I to V, with I being the thumb. - **Phalanges:** The phalanges are the fourteen bones of the fingers. Each finger has three phalanges (proximal, middle, and distal), except for the thumb, which has only two. ## The Lower Limb The lower limb is comprised of the following bones: ### Pelvic Girdle - **Pelvis:** The pelvis is a large, bony structure that connects the lower limbs to the axial skeleton. The pelvis is formed by three bones: the ilium, the ischium, and the pubis. ### Thigh - **Femur:** The femur, or thigh bone, is the longest and strongest bone in the human body. It connects the hip joint at its proximal end and the knee joint at its distal end. ### Leg - **Tibia:** The tibia, or shin bone, is the larger, medial bone in the lower leg. It is located on the inside of the leg and is responsible for bearing the majority of the body’s weight. - **Fibula:** The fibula is the smaller bone of the lower leg. The fibula is located on the outside of the leg and provides support for the ankle joint. ### Foot The foot is comprised of the following: - **Tarsals:** The tarsals are seven short bones in the ankle. The tarsals are numbered I to VII, with I being the big toe. - **Metatarsals:** The metatarsals are the five long bones of the foot. - **Phalanges:** The phalanges are the fourteen bones of the toes. Each toe has three phalanges (proximal, middle, and distal), except for the big toe, which has only two. # Thank you.