Anatomy of the Skeletal System

Skeletal system facts 206 bones in an adult (~ 350 cartilaginous bones as a developing baby) Skeleton reaches full maturity by age 25 Supports the body and protects vital organs Manufactures blood cells at a rate of 1.2 million per second Allows body movement by connecting with skeletal muscles

Skeletal system facts Stores excess minerals – primarily calcium and phosphorous Ligaments connect bone to bone Tendons connect bone to muscle 2 broad divisions – axial and appendicular

Axial Skeleton Includes the head (cranial and facial), spine, and thorax 80 bones total Primary function is to support and protect the internal organs

Bones of the Head Cranial Bones Made of 8 bones – parietal (2), temporal (2), frontal, occipital, sphenoid, ethmoid Fit tightly together without moveable joints One purpose is to protect the brain and other organs located in the cranium

Bones of the Head Cranial Bones When born, joints are not fused – instead connected by cartilage called fontanels (makes the “softspot”) Skull growth is not complete until age four Areas where bones join are the sutures Jagged edge of sutures gives added strength

Bones of the Head Facial Bones Made of 14 bones – maxilla (2), zygomatic (2), palatine (2), nasal (2), lacrimal (2), inferial nasal concha (2), mandible, vomer Maxilla and palatine form upper jaw and the roof of the mouth Mandible forms the lower jaw – only moveable bone in the skull

Bones of the Head Auditory Bones Made of 6 bones – malleus (2), incus (2), stapes (2) Also known as the hammer, anvil, and stirrup Smallest bones in the body Necessary for hearing

Bones of the Head Hyoid (1) Only bone that does not articulate with another bone U-shaped A point of articulation for many muscles (ex: tongue, pharynx) Found just above the larynx

Bones of the Spine Vertebral Column (general information) Vertebrae – plural; vertebra – singular Made of 26 vertebrae (originally 34, but 5 sacral bones fuse together and 4-5 coccygeal bones fuse together. Intervertebral disks allow the spine to bend and act as shock absorbers – made of cartilage Have a hollow area for the spinal cord to pass through

Bones of the Spine Cervical Vertebrae First 7 vertebrae – make up the neck (C1-C7) C1 – atlas Point where the head is connected to the spine Allows the head to pivot up and down C2 – axis Located right below the atlas Allows the head to swivel left to right Other cervical vertebrae allow the head to tilt and move in other directions

Bones of the Spine

Bones of the Spine Thoracic Vertebrae Made of 12 vertebrae (T1-T12) Larger than the cervical vertebrae Attachment point for the ribs

Bones of the Spine Lumbar Vertebrae Made of 5 vertebrae (L1-L5) Largest vertebrae Form the lower back Support the weight of the entire upper body

Bones of the Spine Sacral Vertebrae (or Pelvic Vertebrae) Made of 5 vertebrae fused together (in adults) Also called the sacrum Joined to the hips to form the base of the spine

Bones of the Spine Coccyx Made of 4-5 vertebrae fused together (in adults) Also called the tailbone or coccygeal vertebrae Used for muscle attachment and a shock absorber for the spine

Curvature of the Spine Four curves Cervical lordosis Thoracic kyphosis Lumbar lordosis Sacral/coccygeal curve

Curvature of the Spine Provide additional strength and flexibility Can have excess curvature Scoliosis – excessive lateral curvature Kyphosis – excessive thoracic curvature (humpback) Lordosis – excessive lumbar curvature (swayback)

Bones of the Chest Ribs Made of 24 bones (12 pairs) Attaches to the thoracic vertebrae in the back and by cartilage to the sternum in front (the first 7 pairs) Cartilage is flexible so the ribs can expand and contract during breathing

Bones of the Chest 3 types of ribs True ribs- first 7 pairs, attach directly to the sternum False ribs – next 3 pairs, attaches to the lowest true rib by cartilage Floating ribs – last 2 pairs, do not attach to the sternum at all, also considered false ribs

Bones of the chest

Bones of the Chest Sternum Known as the breast bone Contains the manubrium, body, and xiphoid process Last bone to ossify

Appendicular Skeleton General Information Includes the shoulders, hips, arms, and legs 126 bones total Primary function is support and to enable movement

Bones of the Shoulder Consists of 4 bones Also known as the pectoral girdle

Bones of the Shoulder Scapulae (2) Clavicle (2) Singular is scapula Also known as the shoulder blades Contains sockets for the arms Don’t rigidly attach to the axial skeleton Only articulate with the humerus and clavicle Clavicle (2) Also known as the collar bone Articulates with the scapula and the sternum

Bones of the Upper Extremities Consists of 60 bones Only 6 are in the arms with the rest in the wrists, hands, and fingers

Bones of the Upper Extremities Humerus (2) Makes the upper arm Articulates with the scapula, ulna, and radius

Bones of the Upper Extremities Forearm Consists of 4 bones Radius (2) Located on the lateral side of the forearm (thumb side) Rotates over the ulna Ulna (2) Locaed on the medial side of the forearm (little finger side) Does not move when the arm is rotated Has a “hook” to attach to the humerus

Bones of the Upper Extremities Wrist The bones as a group are known as the carpals Consists of 16 bones (8 on each side) – pisiform, lunate, scaphoid, trapezium, trapezoid, capitate, hamate, triquetrium The bones are arranged in two rows of 4 This allows the wrist to bend in various directions

Bones of the upper extremities

Bones of the Upper Extremities Hands and Fingers Consists of 38 bones Metacarpals These make up the palm of the hand There are 10 of these bones (5 per side) The metacarpal that makes up the thumb is held by ligaments that give it great mobility Phalanges 28 phalanges make up the fingers (14 per side) 3 in each finger, 2 for each thumb

Bones of the upper extremities

Bones of the Pelvic Girdle The pelvic girdle is made of a ring of bones: the sacrum makes up the back and the sides are made up of a pair of bones called the coxae Each coxae is really three bones fused together: ilium, ischium, pubis Coxae, coxal bone, and pelvic bone all refer to the same thing

Bones of the pelvic girdle

Bones of the Lower Extremities Similar in basic layout to the upper extremities Bones are thicker and stronger than in the upper extremities Each lower limb has 30 bones – 4 in the leg and 26 in the foot and ankle

Bones of the Lower Extremities Bones of the Leg Femur Makes up the thigh Longest bone in the body Strongest bone in the body Attaches to the pelvic girdle at the hip joint

Bones of the Lower Extremities Tibia One of the bones in the lower leg The main weight bearing bone of the leg Extends from the knee to the ankle Fibula Much thinner than the tibia Found on the lateral side Does not attach to the femur

Bones of the Lower Extremities Patella Kneecap Found on top of the joint between the femur and the tibia Serves as a brace for the patellar tendon to increase leverage on the joint Also helps to protect the joint from injury

Bones of the Lower Extremities Bones of the Ankle and Foot Tarsals Make up the ankle 14 bones (7 per side): talus, calcaneus (heel bone), navicular, cuboid, and 3 cuneiform Thick and strong to support the weight of the body Talus connects with the tibia

Bones of the Lower Extremities Metatarsals Make up the base of the foot Made of 10 bones (5 per side) Forms the framework of the arches of the foot Phalanges Made of 28 bones (14 per side) Makes up the toes Arranged like the phalanges in the fingers: 2 in each big toe, 3 in every other toe

Bones of the lower extremities