ANATOMY
THE DESIGN OF ORGANISMS
The head is positioned upon the superior portion of the vertebral column, attaching the skull upon C-1 (the first cervical vertebra known as the atlas). The skeletal section of the head and neck forms the superior segment of the axial skeleton and comprises skull, hyoid bone, auditory ossicles, and cervical spine. The skull can be further subdivided into: (a) cranium (8 bones: frontal, 2-parietal, occipital, 2-temporal, sphenoid, ethmoid), and
(b) facial bones (14 bones: 2-zygomatic, 2-maxillary, 2-palatine, 2-nasal, 2-lacrimal, vomer, 2-inferior conchae, mandible). As the fetus develops, the facial bones usually form into pairs, and then fuse together. As the cranium fuses, sutures are formed that resemble stitching between bone plates. In a newborn, the junction of the parietal bones with the frontal and occipital bones. anterior (front) and posterior (back) fontanelle, or soft spots. tion of the
The brachiocephalic artery or trunk is the first and largest artery that branches to form the right common carotid artery and the right subclavian artery. This artery provides blood to the right upper chest, right arm, neck, and head, through a branch called right vertebral artery. The right and left vertebral artery feed into the basilar artery and upward to the Posterior cerebral artery, which provides most of the brain with oxygenated blood. The posterior
cerebral artery and the posterior communicating artery are within the circle of Willis. The left common carotid artery divides to form the: internal carotid artery (ICA) and an external carotid artery (ECA). The ICA supplies the brain. The ECA supplies the neck and face. The left subclavian artery and the right subclavian artery, one on each side of the body form the internal thoracic artery, the vertebral artery.
In human anatomy, the arm is the upper limb of the body, comprising regions between the glenohumeral joint (shoulder joint) and the elbow joint. In common usage the arm extends to the hand. It can be divided into the upper arm (brachium), the forearm (antebrachium), and the hand (manus). Anatomically the shoulder girdle with bones and corresponding muscles is by definition a part of the arm. The Latin term brachium may refer to both the arm as a whole or to the upper arm on its own. The humerus is one of the three long bones of the arm. It joins with the
scapula at the shoulder joint and with the other long bones of the arm, the ulna and radius at the elbow joint. The elbow is the hinge joint between the end of the humerus and the ends of the radius and ulna. The humerus cannot be broken easily. Its strength allows it to handle loading up to 300 pounds (140 kg). The arm is divided by a fascial layer (known as lateral and medial intermuscular septa) separating the muscles into two osteofascial compartments: the anterior and the posterior compartments of the arm. The fascia merges with the periosteum (outer bone layer)
A hand (Latin manus) is a prehensile, multi-fingered organ located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each “hand” and fingerprints remarkably similar to human fingerprints) are often described as having “hands” instead of paws on their front limbs. The raccoon is usually described as having “hands” though opposable thumbs are lacking. Fingers contain some of the densest areas of nerve endings on the body, are the richest source of tactile feedback, and have the greatest positioning capability of the body; thus the sense of touch is intimately associated with hands. Like other paired organs (eyes, feet, legs) each hand is dominantly controlled by the opposing brain hemisphere, so that handedness—the preferred hand choice for single-handed activities such as writing with a
pencil, reflects individual brain functioning. Some evolutionary anatomists use the term hand to refer to the appendage of digits on the forelimb more generally — for example, in the context of whether the three digits of the bird hand involved the same homologous loss of two digits as in the dinosaur hand.[2] The human hand has five fingers and 27 bones, not including the sesamoid bone, the number of which varies between people,[3] 14 of which are the phalanges (proximal, intermediate and distal) of the fingers. The metacarpal bones connect the fingers and the carpal bones of the wrist. Each human hand has five metacarpals[4] and eight carpal bones. Among humans, the hands play an important function in body language and sign language. Many mammals and other animals have grasping appendages similar in form to a hand such as paws.
The genetic information passed from The genetic information passed from parent to offspring is contained in genes parent to offspring is contained in genes carried by chromosomes in the nucleus. carried chromosomes in the offspring nucleus. Sexual by reproduction produces Sexual reproduction produces that resemble their parents, butoffspring are not that resemble their parents, but are not identical to them. identical them. their parents because Offspringtoresemble Offspring resemble parents because they contain genetictheir information passed they genetic information passed on tocontain them by their parents. on to them by their parents. Chromosomes, found in the cell nucleus, Chromosomes, found in the cell contain many genes. A gene is anucleus, section of contain manycarries genes.coding A genefor is aa particular section of DNA, which DNA, which carriesgenes coding for a particular protein. Different control the develprotein. genes control the of developmentDifferent of different characteristics an opment of different characteristics of an organism. Many genes are needed to carry organism. Manyinformation genes are needed to carry all the genetic for a whole all the genetic information for a whole organism. organism. Although individuals of a species look Although individuals of a species look
similar, they are not usually identical: these similar, they are are called not usually identical: these differences variation. differences are called variation. Variation due to genetic causes is inheritVariation dueFor to genetic causes is inherited variation. example, children usually ed variation. For example, children usually look a little like their father, and a little like look little likebut their father, andbe a little like theiramother, they will not identical their mother, but parents. they will This not be identical to either of their is because to either of their parents. This is because they get half of their inherited features they half of their inherited features fromget each parent. from parent. Someeach variation within a species is inheritSome variation within a species inherited, and some variation is due toisthe envied, and some variation is is due toto the environment; some variation due a combironment; nation of some both. variation is due to a combination of both. vary because of a combinaSome features Some because of a combination offeatures geneticvary causes and environmental tion of genetic causes and environmental causes. For example, identical twins inherit causes. identical twins inherit exactly For the example, same genetic information from exactly the same genetic information from their parents. their parents.
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