The animal kingdom
Voyages on a Vespa. Environmental Toxicology and Pharmacology 6: Other back to top. With the exception of the singular sacrum and coccyx, each vertebra is named for the first letter of its region and its position along the superior-inferior axis. There are very low levels of Y-chromosome variability,   but a great deal of genetic variation in mitochondrial DNA.
A definition of animals
Among all the health benefits of calcium, the most important ones are that it aids in maintaining bone and dental health, as well as helps in the prevention of colon cancer and the reduction of obesity. Finally, when we get older, our bones tend to get porous and weak, thereby requiring ample calcium intake. With so many fancy diets around us, we often tend to avoid calcium-rich foods like whole food groups, including dairy products.
Reports say that calcium deficiency conditions are continuously rising, particularly in women who are on low-calorie diets to get slim and are, therefore, confronted with the threat of osteoporosis. Thus, it is extremely important to consume enough calcium, vitamin D , magnesium , and K2 throughout your life.
It has some very obvious symptoms, including the following:. Thus, a regular supply of calcium is very important in growing children and teenagers as it can substantially reduce the risks of osteoporosis in old age.
Osteoarthritis is a common ailment in one out of every three women and in one man in every 12, above 50 years of age. It is also worth noting that semi-skimmed and whole milk have very similar calcium contents. Calcium strengthens the backbone, helps alleviate the presence of back pain , and keeps the bones in their proper shape.
Calcium efficiently helps in maintaining optimal body weight in both males and females. This maintains the balance. On the other side, the parathyroid hormone also stimulates the production of fat and prevents its break down, which can subsequently make you obese.
Basically, make sure that you are taking the right amount of calcium so that obesity does not creep in. It protects your heart muscles. If there is a calcium drop, a hormone called calcitriol is released, which contracts the smooth muscles of the arteries, thereby increasing the blood pressure. Cardiac muscles need extracellular calcium ions for contraction. When the intracellular concentration of calcium increases, the ions gather together on the protein troponin.
The malleus, incus, and stapes—known collectively as the auditory ossicles —are the smallest bones in the body. Found in a small cavity inside of the temporal bone, they serve to transmit and amplify sound from the eardrum to the inner ear. Twenty-six vertebrae form the vertebral column of the human body. They are named by region:. With the exception of the singular sacrum and coccyx, each vertebra is named for the first letter of its region and its position along the superior-inferior axis.
For example, the most superior thoracic vertebra is called T1 and the most inferior is called T The sternum, or breastbone, is a thin, knife-shaped bone located along the midline of the anterior side of the thoracic region of the skeleton. The sternum connects to the ribs by thin bands of cartilage called the costal cartilage. There are 12 pairs of ribs that together with the sternum form the ribcage of the thoracic region. The pectoral girdle connects the upper limb arm bones to the axial skeleton and consists of the left and right clavicles and left and right scapulae.
The humerus is the bone of the upper arm. It forms the ball and socket joint of the shoulder with the scapula and forms the elbow joint with the lower arm bones. The radius and ulna are the two bones of the forearm. The ulna is on the medial side of the forearm and forms a hinge joint with the humerus at the elbow.
The radius allows the forearm and hand to turn over at the wrist joint. The lower arm bones form the wrist joint with the carpals, a group of eight small bones that give added flexibility to the wrist. The carpals are connected to the five metacarpals that form the bones of the hand and connect to each of the fingers. Each finger has three bones known as phalanges, except for the thumb, which only has two phalanges. Formed by the left and right hip bones, the pelvic girdle connects the lower limb leg bones to the axial skeleton.
The femur is the largest bone in the body and the only bone of the thigh femoral region. The femur forms the ball and socket hip joint with the hip bone and forms the knee joint with the tibia and patella. Commonly called the kneecap, the patella is special because it is one of the few bones that are not present at birth. The patella forms in early childhood to support the knee for walking and crawling. The tibia and fibula are the bones of the lower leg.
The fibula is mainly a muscle attachment point and is used to help maintain balance. The tibia and fibula form the ankle joint with the talus, one of the seven tarsal bones in the foot. The tarsals are a group of seven small bones that form the posterior end of the foot and heel.
The tarsals form joints with the five long metatarsals of the foot. Then each of the metatarsals forms a joint with one of the set of phalanges in the toes. Each toe has three phalanges, except for the big toe, which only has two phalanges. Living bone cells are found on the edges of bones and in small cavities inside of the bone matrix. Although these cells make up very little of the total bone mass, they have several very important roles in the functions of the skeletal system.
The bone cells allow bones to:. All of the bones of the body can be broken down into five types: The long bones of the body contain many distinct regions due to the way in which they develop. At birth, each long bone is made of three individual bones separated by hyaline cartilage. The epiphyses and diaphysis grow towards one another and eventually fuse into one bone.
Once the long bone parts have fused together, the only hyaline cartilage left in the bone is found as articular cartilage on the ends of the bone that form joints with other bones. The articular cartilage acts as a shock absorber and gliding surface between the bones to facilitate movement at the joint.
Looking at a bone in cross section, there are several distinct layered regions that make up a bone. The outside of a bone is covered in a thin layer of dense irregular connective tissue called the periosteum.
The periosteum contains many strong collagen fibers that are used to firmly anchor tendons and muscles to the bone for movement. Stem cells and osteoblast cells in the periosteum are involved in the growth and repair of the outside of the bone due to stress and injury. Blood vessels present in the periosteum provide energy to the cells on the surface of the bone and penetrate into the bone itself to nourish the cells inside of the bone.
The periosteum also contains nervous tissue and many nerve endings to give bone its sensitivity to pain when injured. Deep to the periosteum is the compact bone that makes up the hard, mineralized portion of the bone. Compact bone is made of a matrix of hard mineral salts reinforced with tough collagen fibers. Many tiny cells called osteocytes live in small spaces in the matrix and help to maintain the strength and integrity of the compact bone.
Deep to the compact bone layer is a region of spongy bone where the bone tissue grows in thin columns called trabeculae with spaces for red bone marrow in between. The trabeculae grow in a specific pattern to resist outside stresses with the least amount of mass possible, keeping bones light but strong.
Long bones have a spongy bone on their ends but have a hollow medullary cavity in the middle of the diaphysis. The medullary cavity contains red bone marrow during childhood, eventually turning into yellow bone marrow after puberty. An articulation, or joint, is a point of contact between bones, between a bone and cartilage, or between a bone and a tooth. Synovial joints are the most common type of articulation and feature a small gap between the bones.
This gap allows a free range of motion and space for synovial fluid to lubricate the joint. Fibrous joints exist where bones are very tightly joined and offer little to no movement between the bones.