Skeletal System

Bones of the Head and Neck

The skeletal system of the head and neck plays an important role in protecting the brain and all of its attachments that get sent throughout the rest of the body. The head and neck make up the top portion of the axial skeleton. The skull is the bony section of the head and consists of cranium and facial bones. The skull encases and protects the brain, houses the brain senses, provides attachments for muscles of the head and neck, and helps to form the first portions of the respiratory and digestive tracts. The skull rests on the first vertebra, which is called the atlas. At birth, the skull is large in comparison to the rest of the body, and a baby's skull is compressible. The soft spots in a baby's head harden and grow together until the bones meet and mesh like a jigsaw puzzle.

Bones of the Chest and Upper Back

The skeletal system of the upper abdomen surrounds important organs such as the heart, lungs, and others above the diaphragm. The portion of the spine in the upper abdomen is made up of bones called the thoracic vertebrae. These are the twelve vertebrae in the chest area. They have facets on the sides of their bodies that join with the ribs.

Bones of the Pelvis and Lower Back

The skeletal system of the lower abdomen, including the pelvis helps protect the spinal cord, digestive and urogenital systems and other internal organs such as the bladder, rectum, and in women, the uterus.

Bones of the Arm and Hand

The skeletal system of the upper extremities includes the shoulders, arms, hands and fingers. These bones allow for movement in the upper limbs. Out of all of the bones in this region, the clavicle, or collarbone, is the only bone attached to the central skeleton. The two clavicles join the top of the sternum to the scapula, allowing for the support of the rest of the limb. With the help of muscles, these bones keep the limb anchored to the axial skeleton.

Bones of the Leg and Foot

The skeletal system of the lower extremities includes the legs, feet and toes. This subsystem supports the muscles that help with running, walking, standing and more. The weight of the body is transmitted to the legs through the pelvic girdle at sacroiliac joints. These joints, along with the ligaments attached to them, anchor the lower limbs to the axial skeleton.

Nervous System

Nerves of the Abdomen, Lower Back and Pelvis

It is within the nervous system of the lower abdomen that the central nervous system ends and the last vestiges of the spinal cord branch out into the peripheral nervous system. Since the vertebrae continues growing later into a child's development than does the spinal cord, the spinal cord actually ends well up inside the last several vertebrae. The lattermost nerve bundles thus descend through and exit the column vertically, unlike the fairly horizontal passages of the vertebral foramina in the thoracic and cervical vertebrae.

Nerves of the Chest and Upper Back

The nervous system of the upper abdomen (the chest) is a critical part of the nervous system as a whole, as the nerve bundles are second in importance only to the brain itself. Within it, substantial percentages of the body's locomotion, balance, and sensory information are sent and received through motor and sensory nerves to communicate between the central nervous system and peripheral nervous system.

Nerves of Head and Neck

Within the skeletal structures of the head and the neck lie the most significant portions of the human nervous system. The whole of the brain and the largest body of the spinal cord are enclosed in this section of the nervous system, from there commanding and receiving messages from the whole of the body.

Nerves of the Arm and Hand

The nerves of the arm and hand perform a substantial two-fold role: commanding the intricate movements of the arms all the way down to the dexterous fingers, while also receiving the vast sensory information supplied by the sensory nerves of the hands and fingers.

Nerves of the Leg and Foot

The nerves of the leg and foot serve to propel the body through the actions of the legs, feet, and toes while maintaining balance, both while the body is moving and when it is at rest. Sensory nerves are of course present throughout the lower extremities; however, with the exception of the bottom of the foot, they play a lesser role here than in the upper extremities. Primarily, this section of the peripheral nervous system sends and receives signals regarding locomotion of the body.

Endocrine System

Endocrine System of the Head and Neck

The endocrine system of the head and neck contains several major glands and sets of glands. These are responsible for releasing hormones into the bloodstream; from there, the hormones are transported to organs and tissues throughout the entire body. The glands in this part of the endocrine system are the hypothalamus, the pineal gland, the pituitary gland and the thyroid and parathyroid glands.

Endocrine System

The endocrine system of the upper abdomen and chest has only one major set of glands: the thymus. The thymus is a gland that forms part of the immune system; it produces the body's T-lymphocytes, also called T cells. The heart and the adipose tissue within the chest also secrete some important hormones: the heart produces peptides, which help regulate blood pressure, while the adipose tissue secretes hormones which regulate appetite and metabolism.

Hypothalamus

The hypothalamus is a tiny cluster of brain cells, just above the pituitary gland, which transmits messages from the body to the brain. It effectively uses the pituitary gland to link the nervous system to the endocrine system.

Reproductive System

Female Breasts

In the upper abdomen and chest, the female reproductive system is primarily represented by the breasts. The breasts serve a number of functions, mainly after pregnancy: the mammary glands are accessory organs of the female reproductive system which are specialized to secrete milk following pregnancy. A nipple is located near the tip of each breast, and it is surrounded by a circular area of pigmented skin called the areola.

Reproductive Organs of the Lower Torso

The female reproductive system of the lower abdomen and pelvis contains all of the organs necessary for initiating fertilization and bringing the resultant pregnancy to term. Most of these are housed within the abdominal cavity or pelvic area, but the vulva (the opening to the vagina) is made up of several smaller parts which are external. The ovaries produce and release eggs which move along the fallopian tubes to the uterus; the uterus is a hollow, muscular organ in which a fertilized egg is nourished until birth. The vagina is a muscular passage which forms a part of the female sex organs; it connects the neck of the uterus (called the cervix) with the external genitals.

Fertilization and Pregnancy

Fertilization is the first step in pregnancy. The ovaries are a pair of oval or almond-shaped glands that lie on either side of the uterus and just below the opening to the fallopian tubes. These contain the eggs, also known as ova (singular: ovum). The fallopian tubes lie in the pelvic portion of the abdominal cavity and each tube reaches from an ovary to become the upper part of the uterus. This funnel-shaped tube is about three inches in length; it carries eggs and sperm, and is where fertilization of the egg takes place. The larger end of the funnel is divided into feathery, finger-like projections, which lie close to the ovary. These beating projections, along with muscle contractions, force the ovum down the funnel's small end, which opens into the uterus. After sexual intercourse, sperm swim up this funnel from the uterus. The lining of the tube and its secretions sustain both the egg and the sperm, encouraging fertilization and nourishing the egg until it reaches the uterus.

Birth and Infancy

Birth, also known as childbirth, parturition or partus, is the end point of pregnancy and results in the expulsion of newborn infants from the pregnant woman's uterus. Birth has three stages of labor: the cervix's shortening and dilation, the descent and birth of the infant, and the expulsion of the placenta. Birth can also be done via caesarean section; this is the removal of the newborn through a surgical incision in the abdomen, instead of through the vagina.

Respiratory System

Respiratory System of the Head and Neck

The respiratory system of the head and neck marks the starting point for where oxygen enters the body. The system begins at the nose and mouth where oxygen is inhaled. The areas of the respiratory in the head and neck allow air to flow in and out of the lungs.

Lungs and Resporatory System of the Chest

The respiratory system in the upper abdomen and chest area is where the intake of oxygen from the nose and mouth ends and is processed by the lungs. The human body needs oxygen to provide energy and growth to body cells to keep the cells alive. The respiratory system and the lungs help oxygen to enter the body as well as secrete carbon dioxide, the waste produced after the body has processed the oxygen.