Quiz and Crossword Combo #2: Body Parts

Answer: Spine

There are thirty-three vertebrae in a human's vertebral column. The upper twenty-four articulate and each have inter-vertebral discs between these bones, but the lower nine are fused in adults (five in the sacrum and four in the coccyx).

The spine is divided into regions called the cervical spine, thoracic spine, lumbar spine, sacrum and coccyx. There are seven cervical vertebrae, twelve thoracic vertebrae and five lumbar vertebrae. The number of these in the cervical region is only rarely different in mammals, with the exceptions being the two sloth genera and the manatee genus. All other mammals have seven cervical vertebrae, even the giraffe but those seven vertebrae are very tall - up to 25cm.

In other vertebrates, the number of cervical vertebrae can range from one cervical vertebra in amphibians, to 25 in swans.

With lower articulating vertebrae, those attached to the ribs are called thoracic vertebrae, while those without ribs attached, are called lumbar vertebrae.

Answer: Arm

The arm is a complex anatomical structure consisting of three long bones, the humerus in the upper arm, and the ulna and radius (lower arm), which attach to the humerus via tendons. The ulna and radius attach to the bones of the wrist. By definition the shoulder girdle, with bones and corresponding muscles, are considered part of the arm. With a rotating joint at the shoulder and a hinge joint at the elbow the arm is one of the most complex and flexible parts of the body.

The so-called funny bone does not exist and is actually the ulnar nerve, a nerve that runs from the neck to the hand, where it innervates muscles in the hand and forearm. At the elbow it is unprotected which is why it hurts so much when you knock it. There are two theories regarding why it is called the funny bone: One theory is that it is an anatomical pun, because the nerve runs along the humerus, which sounds like "humorous." The other theory claims that the nerve got its nickname because of the funny (as in weird) feeling you feel after hitting it.

Answer: Elbow

The elbow is the middle part of the arm and contains the olecranon, the elbow pit, the lateral and medial epicondyles, and the elbow joint.
The elbow is a complex series of levers and is found only in primates and humans. Some other species, such as dogs, may have so-called elbows but this is an incorrectly applied term.

The olecranon is the large, thickened, curved preeminence of the ulna, one of the two long bones in the forearm that extend into the elbow. This is the pointy portion of the elbow and is opposite to the elbow pit (cubital fossa). The olecranon is a lever for the extensor muscles that straighten the elbow joint. Epicondyles are bony protuberance on the humerus which serve as a site for ligament attachment. The joint itself is a hinge joint but it is also a synovial joint, which is a closed system containing synovial fluid for easier movement of the joint.

Answer: Thumb

The thumb, or pollex, is a finger (you have five fingers on one hand). They are all phalanges with hinge joints, a nail on one side and fingerprints on the other. However the thumb is a specialised finger and has some distinct differences:

- Is opposable to the other four fingers (you can touch your thumb to the other four fingers).
- There are two phalanges rather than three, that is, only one joint.
- It has greater width in the distal phalanx than in the proximal phalanx (ie it is stronger than fingers).
- The thumb is attached, unlike the other fingers, to a metacarpus which moves which in turn produces most of the opposability.

Much has been made about the opposable thumb with claims that this feature separates us from other mammals and is why humans have been able to create tools. However, other primates have opposable thumbs but do not have the functionality of the human thumb. This is thought to be due to grips needed by different species. A crude analogy is that other primates need to swing through trees where an opposable thumb would hinder movement. Some primates use a prehensile tail to pick up objects, so a thumb is not as necessary as to those species without a prehensile tail.

The big toe has a similar sounding name and is called the hallux.

Answer: Heart

The chest boundaries are the shoulder bones above and the diaphragm below. The heart and lungs and attendant structures cram themselves into the chest. It also contains the oesophagus, which is essentially a tube carrying the food to a lower place where digestion can continue. The left lung only has two lobes, compared to the right lung which has three. This is to accommodate the heart which is the size of a fist and is located just left of the mid-line.

In the chest, (or thorax), and abdomen, the ribs surround vital organs and protect them. All ribs extend from the axial vertebral column but only the top seven pairs (true ribs) attach to the sternum (via costal cartilage), the bony plate in front of the chest. The bottom four pairs, the false ribs, do not attach, but rib pairs eight and nine meet the seventh pair of ribs via costal cartilage. The bottom two pairs of false ribs are called floating ribs as they are only attached to the thoracic vertebrae. The sternum is called the breastbone.

Answer: Wrist

The wrist is a complex series of bones and tissues that connect the five metacarpal bones of the hand with the long bones of the forearm, the radius and ulna. There are eight carpal bones in the wrist divided into two groups:

Proximal: scaphoid, lunate, triquetrum, pisiform
Distal: trapezium, trapezoid, capitate, hamate

The five metacarpals make a total of 13 bones in the wrist altogether.
There are two joints on the proximal side: the proximal radioulnar joint and the distal radioulnar joint, which permit pronation and supination. There is also another joint on the proximal side: radiocarpal joint.

Answer: Thigh

The thigh is quite possibly the most under-estimated body part of the human body. It contains a single bone called the femur - the longest and strongest in the human body - but it has two complex joints at either end, the ball and socket hip and the synovial joint of the knee. The ability of the human to walk on two legs centres around these two joints and the powerful musculature between the two.

The thigh comprises three separate compartments, divided by fascia (fibrous sheets), each containing many muscles which use the femur as an axis. Each
fasciated compartment contains a different group of muscles which in turn are responsible for the three types of movement associated with the thigh: abduction/adduction (movement away from/towards the mid-line), flexion and extension.

Answer: Eye

The two bony recesses in the skull that house the eyes are the orbits. Of the 22 bones of the skull, there are seven that comprise the orbit: sphenoid; frontal, zygomatic; ethmoid; lacrimal; maxilla; and palatine.

Eyes themselves are a remarkable marker of evolutionary progress. While the appearance of single cells bacteria that had photo-receptor cells to distinguish light from dark appeared 500 million years ago, there is now substantial evidence that the evolution from these to vision as we now know it took less than half a million years. This is a remarkable evolutionary achievement.

Answer: Uvula

The mouth is complex. The hinged lower jaw is the mandible. In the upper part of the mouth, there are actually two palatine bones fused in the centre of the skull. They, along with the two maxilla bones, form the base of the nasal cavity and the roof of the mouth. This is the hard palate. The soft palate is behind that above the throat.

The uvula is the "hanging-downy-thing" at the back of the mouth often mistaken for the tonsils. It is actually at the back of the soft palate and has two major functions: it moves when food is ingested to stop the food entering the nasal cavity, and it has a role in speech, helping to make certain sounds. Among these is the trill in the "R" sound, (not so much in English but in Arabic, for example) which is caused by the uvula vibrating. The uvula also produces saliva to help lubricate the throat.

Answer: Liver

The liver is a wedge shaped organ tucked up under the right side of the diaphragm and surrounded by the lumbar ribs. The liver occupies almost the entire right upper quadrant of the abdomen. The liver is the factory of the body filtering waste and toxins from foods and metabolising food into usable smaller molecules.

It also regulates glycogen storage, it decomposes red blood cells and produces hormones and bile. Bile is used for the digestion of fats and is stored in the gall bladder which is tucked under the liver.