Re: Human Bones Pictures And Names Pdf Download
Emelina Gilpin
The human skeleton of an adult usually consists of around 206 bones, depending on the counting of sternum (which may alternatively be included as the manubrium, body of sternum, and the xiphoid process).[1] It is composed of 270 bones at the time of birth,[2] but later decreases to 206: 80 bones in the axial skeleton and 126 bones in the appendicular skeleton. 172 of 206 bones are part of a pair and the remaining 34 are unpaired.[3] Many small accessory bones, such as sesamoid bones, are not included in this. The precise count of bones can vary among individuals because of natural anatomical variations.
As a person ages, some bones fuse, a process which typically lasts until sometime within the third decade of life. Therefore, the number of bones in an individual may be evaluated differently throughout a lifetime. In addition, the bones of the skull and face are counted as separate bones, despite being fused naturally. Some reliable sesamoid bones such as the pisiform are counted, while others, such as the hallux sesamoids, are not.
Individuals may have more or fewer bones than the average (even accounting for developmental stage) owing to anatomical variations. The most common variations include sutural (wormian) bones, which are located along the sutural lines on the back of the skull, and sesamoid bones which develop within some tendons, mainly in the hands and feet. Some individuals may also have additional (i.e., supernumerary) cervical ribs or lumbar vertebrae. Amputations or other injuries may result in the loss of bones. Complete bone fractures may split one bone into multiple pieces. Other genetic conditions may result in abnormally higher (e.g. polydactyly or conjoined twins) or lower (e.g. oligodactyly) counts of bones.
The axial skeleton, comprising the spine, chest and head, contains 80 bones. The appendicular skeleton, comprising the arms and legs, including the shoulder and pelvic girdles, contains 126 bones, bringing the total for the entire skeleton to 206 bones. Infants are born with about 270 bones[4] with most of it being cartilage, but will later fuse together and decrease over time to 206 bones.
Lucy was found by Donald Johanson and Tom Gray on November 24, 1974, at the site of Hadar in Ethiopia. They had taken a Land Rover out that day to map in another locality. After a long, hot morning of mapping and surveying for fossils, they decided to head back to the vehicle. Johanson suggested taking an alternate route back to the Land Rover, through a nearby gully. Within moments, he spotted a right proximal ulna (forearm bone) and quickly identified it as a hominid. Shortly thereafter, he saw an occipital (skull) bone, then a femur, some ribs, a pelvis, and the lower jaw. Two weeks later, after many hours of excavation, screening, and sorting, several hundred fragments of bone had been recovered, representing 40 percent of a single hominid skeleton.
The term hominid refers to a member of the zoological family Hominidae. Hominidae encompasses all species originating after the human/African ape ancestral split, leading to and including all species of Australopithecus and Homo. While these species differ in many ways, hominids share a suite of characteristics that define them as a group. The most conspicuous of these traits is bipedal locomotion, or walking upright.
Evidence now strongly suggests that the Hadar material, as well as fossils from elsewhere in East Africa from the same time period, belong to a single, sexually dimorphic species known as Australopithecus afarensis. At Hadar, the size difference is very clear, with larger males and smaller females being fairly easy to distinguish. Lucy clearly fits into the smaller group.
Although several hundred fragments of hominid bone were found at the Lucy site, there was no duplication of bones. A single duplication of even the most modest of bone fragments would have disproved the single skeleton claim, but no such duplication is seen in Lucy. The bones all come from an individual of a single species, a single size, and a single developmental age. In life, she would have stood about three-and-a-half feet tall, and weighed about 60 to 65 pounds.
Bone markings are crucial for identifying bones and understanding anatomy. These distinctive features benefit various professionals, including clinicians and forensic scientists. Bone markings are easily overlooked but serve essential functions like facilitating joint movement, locking bones in place, and supporting and protecting soft tissues.
Bone markings arise through a combination of genetic programming, mechanical stimuli, and adaptation to functional demands, resulting in a diverse array of features that serve various anatomical and physiological roles.[1][2] Bone markings hold significant importance in surgery as they serve as crucial landmarks for surgical procedures.[3] Surgeons rely on bone markings to guide incisions, identify anatomical structures, and navigate around critical areas such as nerves and blood vessels. On the other hand, maladaptive bony prominences can impair normal anatomical function and contribute to musculoskeletal dysfunction and pain. Understanding bone markings enables clinicians to evaluate and manage various musculoskeletal conditions.
Common bone markings are distinctive features on bone surfaces that serve various anatomical, functional, and developmental roles. These markings provide essential reference points for understanding skeletal structure, identifying specific bones, and comprehending their interactions within the body (see Image. Labeled Bone Markings). The following are common bone markings:
The upper limb is involved in a wide range of movements essential for daily activities and physical function. Thus, the upper limb's bone markings are particularly relevant for clinical and anatomical study.
The scapula serves as the upper limb's mobile platform. One can think of this bone as a massive construction crane with jacks that anchor the cab to the ground, like how muscles and connective tissues attach the scapula to the body. The crane also has a long, mobile arm, resembling the upper limb. The scapula has medial, lateral, and superior borders. The inferior pole is the junction of the medial and lateral borders.
The acromion (acromial process) lies at the scapular spine's lateral end. The acromial process is one of the deltoid muscle's proximal insertion sites. The deltoid is a triangular muscle named after the capital Greek letter delta. The scapula's medial border is an insertion site for the rhomboid minor and major muscles. The teres minor originates from the scapula's lateral border, while the teres major arises from the inferior scapular angle.
The humeral midshaft's lateral surface exhibits the deltoid tuberosity, the deltoid insertion site. This muscle abducts the arm beyond the first 15 to 20. The deltoid's anterior fibers rotate the arm medially, while the posterior fibers laterally rotate the arm.[10]
The humeral midshaft's posterior aspect demonstrates the radial spiral groove, which ordinarily lies between the triceps brachii's lateral and medial heads. This groove transmits the radial nerve and profunda brachii artery.
The arm bone's inferior aspect contains the lateral and medial epicondyles. The lateral supracondylar ridge, which contains the proximal insertion point of the brachioradialis and extensor carpi radialis longus, flows into the lateral epicondyle. The lateral epicondyle is a bony prominence where the extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris originate.
The olecranon fossa lies on the arm bone's posterior aspect between the lateral and medial epicondyles. This region receives the ulna's olecranon process at the elbow joint. The distal humeral articulating surfaces include the laterally located capitulum (Latin for "little head") and the trochlea (Greek for "pulley").[11]
The head comprises the proximal radial end and articulates with the capitulum, allowing rotation for supination (palm up) and pronation (palm down). This mobility, while beneficial, makes the radius susceptible to dislocation, as in "nursemaid's elbow." The radial tuberosity serves as an insertion site for the biceps brachii. The radial shaft leads to the large styloid process at the distal end, where the brachioradialis muscle inserts. The radius articulates with the scaphoid and lunate at the radiocarpal joint.[12]
The proximal ulnar end contains the coronoid process, which articulates with the humeral trochlea. This articulation is strong, only permitting flexion and extension. The ulnar tuberosity is where the brachialis muscle distally inserts. This muscle is a pure forearm flexor.[13] The distally located ulnar head articulates with the radius.
The 8 carpal bones are divided into proximal and distal rows. The proximal wrist bones articulate with the radius. The proximal row includes the scaphoid, which resembles the prow of a ship and articulates with the trapezium distally. The trapezium then connects to the 1st metacarpal bone that supports the thumb. Moving from lateral to medial, the proximal row continues with the lunate (resembling the moon), triquetrum (which has 3 corners), and the rounded pisiform. The pisiform can be palpated on the hand's anterior aspect. This bone moves with hand motion, confirming its location within the wrist rather than the forearm.
The distal carpal row starts with the laterally located trapezium (which resembles a 4-sided figure with 2 parallel sides), articulating with the thumb and index finger metacarpals. Medial to the trapezium is the trapezoid, shaped similarly to the trapezium, and capitate, the largest wrist bone. The hamate is medially located and features a prominent hook. The Guyon canal is the space between the pisiform and the hamate's hook that transmits the ulnar nerve. A hamate hook fracture can damage this nerve.
The 14 finger bones are known as the phalanges, a term derived from the military formation "phalanx." Each finger has 3 phalanges, except the thumb, which has 2. Finger movements include flexion (forward), extension (backward), abduction (finger separation), and adduction (fingers coming together). Metacarpal bones, 1 for each finger, connect the wrist bones to the fingers. The thumb's carpometacarpal articulation is rotated 90 compared to the other fingers, allowing flexion and extension along the plane of the hand. Abduction leads the thumb away from the palm, while adduction brings it toward the palm.[14]
b1e95dc632