Anatomy for Medical Coder- Skeleton
Skeletal System for CPC Fresher
Skeletal System
The skeletal system is the body's framework, made up of bones, cartilage, joints, and ligaments. It provides support, gives shape to the body, protects vital organs, and helps in movement.
An adult human body has total 206 bones and a few cartilages.
The skeletal system is divided into two main parts:
Axial Skeleton – Consists of 80 bones located along the central axis of the body. It includes the skull, vertebral column (spine), ribs, and sternum (breastbone).
Appendicular Skeleton – Consists of 126 bones and includes the upper limbs, lower limbs, shoulder girdle, and pelvic girdle.
Skull
The skull is a bony structure that protects the brain and forms the framework of the face. It is made up of 22 bones, which are divided into two groups:
1. Cranial Bones (8 Bones)
These 8 bones form the cranium, a hard protective covering around the brain.
2. Facial Bones (14 Bones)
These 14 bones form the front part of the skull, including the bones of the face, nose, cheeks, and jaws.
Hyoid Bone
The hyoid bone is a U-shaped bone located at the base of the tongue (above the larynx).
It is unique because it does not articulate with any other bone.
It supports the tongue and helps in swallowing and speech.
Ear Ossicles
Each middle ear contains three tiny bones, collectively called the ear ossicles:
Malleus (Hammer)
Incus (Anvil)
Stapes (Stirrup)
These are the smallest bones in the human body and help transmit sound vibrations from the eardrum to the inner ear.
Smallest bone in the body = Stapes
Skull Articulation
The skull is connected to the first cervical vertebra (atlas) by two occipital condyles. This type of attachment is called a dicondylic skull, allowing the head to nod up and down.
Vertebral Column (Spine)
The vertebral column, also called the spine or backbone, is the main supporting structure of the body. It extends from the base of the skull to the pelvis and forms the central framework of the trunk.
The adult vertebral column consists of 26 bones (vertebrae). Each vertebra has a central opening called the vertebral foramen (neural canal), through which the spinal cord passes.
The first cervical vertebra is called the Atlas (C1). It articulates with the occipital condyles of the skull, allowing the head to nod ("Yes" movement).
The vertebral column is divided into five regions:
Region | Number of Vertebrae | Description |
Cervical | 7 | Neck region (C1–C7) |
Thoracic | 12 | Upper back; attached to ribs (T1–T12) |
Lumbar | 5 | Lower back (L1–L5) |
Sacrum | 5 fused vertebrae (1 bone) | Forms the back part of the pelvis |
Coccyx | 4 fused vertebrae (1 bone) | Tailbone |
Total Vertebrae
Before fusion: 33 vertebrae
After fusion (Adult): 26 bones
Vertebral Column = Spine = Backbone
Adult bones = 26
Original vertebrae = 33
Atlas = C1 (supports the skull)
Axis = C2 (allows head rotation or "No" movement)
Thoracic vertebrae articulate with the ribs
Spinal cord passes through the vertebral canal (neural canal)
Sternum and Ribs (Rib Cage)
The sternum, also called the breastbone, is a flat bone located in the center of the chest (thorax).
Humans have 12 pairs of ribs (24 ribs). Each rib is a thin, curved, flat bone that connects:
Posteriorly (back) to the thoracic vertebrae
Anteriorly (front) to the sternum, either directly or indirectly
Each rib has two articulation surfaces at its posterior end, so it is called a bicephalic rib.
The thoracic vertebrae, ribs, and sternum together form the rib cage.
Types of Ribs
1. True Ribs (1st–7th Pairs)
Total: 7 pairs (14 ribs)
Directly attached to the sternum through hyaline (costal) cartilage.
Also attached to the thoracic vertebrae posteriorly.
2. False Ribs (8th–10th Pairs)
Total: 3 pairs (6 ribs)
Do not attach directly to the sternum.
They connect to the 7th rib through costal cartilage.
3. Floating Ribs (11th–12th Pairs)
Total: 2 pairs (4 ribs)
Attached only to the thoracic vertebrae.
They do not attach to the sternum at the front.
Functions of the Rib Cage
Protects the heart, lungs, and major blood vessels.
Supports the upper body.
Helps in breathing (respiration).
Provides attachment for chest and back muscles.
CPC Exam Tip
Total Axial Bones = 80
Skull Bones = 22 (8 Cranial + 14 Facial)
Smallest Bone = Stapes
Only Movable Skull Bone = Mandible
Largest Facial Bone = Mandible
Strongest Facial Bone = Mandible
Forehead Bone = Frontal
Cheek Bone = Zygomatic
Upper Jaw = Maxilla
Lower Jaw = Mandible
Collar Bone is NOT part of the axial skeleton (it's part of the appendicular skeleton)
Vertebral Column = 26 bones in adults (33 vertebrae before fusion)
Category | Bone Name | Quantity |
Cranial Bones (8) | Frontal | 1 |
Parietal | 2 | |
Temporal | 2 | |
Occipital | 1 | |
Sphenoid | 1 | |
Ethmoid | 1 | |
Total Cranial Bones | 8 | |
Facial Bones (14) | Maxilla | 2 |
Zygomatic | 2 | |
Nasal | 2 | |
Lacrimal | 2 | |
Palatine | 2 | |
Inferior Nasal Concha | 2 | |
Vomer | 1 | |
Mandible | 1 | |
Total Facial Bones | 14 | |
Ear Ossicles (6) | Malleus | 2 |
Incus | 2 | |
Stapes | 2 | |
Total Ear Ossicles | 6 | |
Hyoid Bone (1) | Hyoid | 1 |
Vertebral Column (26) | Cervical Vertebrae (C1–C7) | 7 |
Thoracic Vertebrae (T1–T12) | 12 | |
Lumbar Vertebrae (L1–L5) | 5 | |
Sacrum (5 fused vertebrae) | 1 | |
Coccyx (4 fused vertebrae) | 1 | |
Total Vertebral Column | 26 | |
Thoracic Cage | Sternum | 1 |
Ribs (12 pairs) | 24 | |
Total Thoracic Cage | 25 | |
Total Axial Bone | Total Axial Bone | 80 |
Appendicular Skeleton
The appendicular skeleton consists of the bones of the upper limbs (arms), lower limbs (legs), and their girdles (shoulder and pelvic girdles). It is mainly responsible for movement and locomotion.
The appendicular skeleton contains 126 bones, including:
Upper limbs: 60 bones (30 in each arm)
Lower limbs: 60 bones (30 in each leg)
Pectoral (Shoulder) girdle: 4 bones
Pelvic girdle: 2 hip bones
Bones of the Upper Limb (30 Bones)
Each upper limb consists of 30 bones:
Bone | Number |
Humerus (Upper arm) | 1 |
Radius (Forearm - Thumb side) | 1 |
Ulna (Forearm - Little finger side) | 1 |
Carpals (Wrist bones) | 8 |
Metacarpals (Palm bones) | 5 |
Phalanges (Finger bones) | 14 |
Total | 30 |
Bones of the Lower Limb (30 Bones)
Each lower limb consists of 30 bones:
Bone | Number |
Femur (Thigh bone) | 1 |
Patella (Kneecap) | 1 |
Tibia (Shin bone) | 1 |
Fibula (Outer leg bone) | 1 |
Tarsals (Ankle bones) | 7 |
Metatarsals (Foot bones) | 5 |
Phalanges (Toe bones) | 14 |
Total | 30 |
Tarsal Bones
The tarsal bones are the seven bones that form the ankle and the back part of the foot. They connect the tibia and fibula to the metatarsal bones, providing stability, support, and allowing foot movement during walking and running.
The 7 tarsal bones are:
Talus
Calcaneus
Navicular
Cuboid
Medial Cuneiform
Intermediate Cuneiform
Lateral Cuneiform
CPC Exam Tip
Number of Tarsal Bones = 7
Largest tarsal bone = Calcaneus (Heel bone)
Talus articulates with the tibia and fibula to form the ankle joint.
CPC Exam Tip
Femur is the longest and strongest bone in the human body.
Patella (Kneecap) is the largest sesamoid bone and protects the knee joint.
Radius is located on the thumb side of the forearm.
Ulna is located on the little finger side of the forearm.
Tibia is the weight-bearing bone of the lower leg.
Fibula provides support and muscle attachment but bears very little body weight.
Pectoral (Shoulder) Girdle
The pectoral girdle connects the upper limbs to the axial skeleton.
It consists of:
Clavicle (Collar bone)
Scapula (Shoulder blade)
Scapula (Shoulder Blade)
The scapula is a large, flat, triangular bone located on the back (posterior side) of the chest between the 2nd and 7th ribs.
Important Parts of the Scapula
1. Spine of Scapula
A raised ridge on the back of the scapula.
Divides the scapula into two parts.
2. Acromion Process
A broad projection extending from the spine.
Articulates with the clavicle to form the Acromioclavicular (AC) joint.
3. Glenoid Cavity (Glenoid Fossa)
A shallow socket on the lateral side of the scapula.
Articulates with the head of the humerus to form the shoulder (glenohumeral) joint.
Pelvic Girdle
The pelvic girdle connects the lower limbs to the axial skeleton.
It consists of two hip bones, each formed by the fusion of:
Ilium
Ischium
Pubis
The pelvis supports body weight and protects pelvic organs such as the bladder and reproductive organs.
Acetabulum
The point where the ilium, ischium, and pubis fuse forms a deep socket called the acetabulum.
The head of the femur (thigh bone) fits into the acetabulum to form the hip joint.
Pubic Symphysis
The left and right hip bones meet in the front at the pubic symphysis.
It is a fibrocartilaginous joint.
It provides stability while allowing a small amount of movement.
It becomes more flexible during childbirth.
Category | Bone Name | Quantity |
Pectoral (Shoulder) Girdle (4) | Clavicle | 2 |
Scapula | 2 | |
Total Pectoral Girdle | 4 | |
Upper Limbs (60) | Humerus | 2 |
Radius | 2 | |
Ulna | 2 | |
Scaphoid | 2 | |
Lunate | 2 | |
Triquetrum | 2 | |
Pisiform | 2 | |
Trapezium | 2 | |
Trapezoid | 2 | |
Capitate | 2 | |
Hamate | 2 | |
Metacarpals | 10 | |
Proximal Phalanges (Hand) | 10 | |
Middle Phalanges (Hand) | 8 | |
Distal Phalanges (Hand) | 10 | |
Total Upper Limbs | 60 | |
Pelvic Girdle (2) | Right Coxal (Hip) Bone | 1 |
Left Coxal (Hip) Bone | 1 | |
Total Pelvic Girdle | 2 | |
Bones Forming Each Coxal Bone (Fused – not counted separately in adult) | Ilium | (1 each side) |
Ischium | (1 each side) | |
Pubis | (1 each side) | |
Lower Limbs (60) | Femur | 2 |
Patella | 2 | |
Tibia | 2 | |
Fibula | 2 | |
Talus | 2 | |
Calcaneus | 2 | |
Navicular | 2 | |
Cuboid | 2 | |
Medial Cuneiform | 2 | |
Intermediate Cuneiform | 2 | |
Lateral Cuneiform | 2 | |
Metatarsals | 10 | |
Proximal Phalanges (Foot) | 10 | |
Middle Phalanges (Foot) | 8 | |
Distal Phalanges (Foot) | 10 | |
Total Lower Limbs | 60 | |
Total Appendicular bone | Total Appendicular bone | 126 |
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