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83-411: The sacrum ( pl. : sacra or sacrums ), in human anatomy , is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1–S5) between ages 18 and 30. The sacrum situates at the upper, back part of the pelvic cavity , between the two wings of the pelvis . It forms joints with four other bones. The two projections at the sides of the sacrum are called

166-519: A cell . Here, parts of DNA are copied and sent to the body of the cell via RNA . The RNA is then used to create proteins , which form the basis for cells, their activity, and their products. Proteins dictate cell function and gene expression, a cell is able to self-regulate by the amount of proteins produced. However, not all cells have DNA; some cells such as mature red blood cells lose their nucleus as they mature. The body consists of many different types of tissue , defined as cells that act with

249-420: A number of body cavities , separated areas which house different organ systems. The brain and central nervous system reside in an area protected from the rest of the body by the blood brain barrier . The lungs sit in the pleural cavity . The intestines , liver , and spleen sit in the abdominal cavity . Height, weight, shape and other body proportions vary individually and with age and sex. Body shape

332-399: A number of sexually transmitted infections including syphilis , HIV , chlamydia , HPV and genital warts . Cancer can affect most parts of the reproductive system including the penis , testicles , prostate , ovaries , cervix , vagina , fallopian , uterus and vulva . The respiratory system consists of the nose, nasopharynx , trachea , and lungs . It brings oxygen from

415-505: A specialised function. The study of tissues is called histology and is often done with a microscope . The body consists of four main types of tissues. These are lining cells ( epithelia ), connective tissue , nerve tissue and muscle tissue . Cells that line surfaces exposed to the outside world or gastrointestinal tract ( epithelia ) or internal cavities ( endothelium ) come in numerous shapes and forms – from single layers of flat cells , to cells with small beating hair-like cilia in

498-464: A translation of Greek ἱερόν ὀστέον, the term found in the writings of Galen . Prior to the adoption of sacrum , the bone was also called holy bone in English, paralleling German heiliges Bein or Heiligenbein (alongside Kreuzbein ) and Dutch heiligbeen . The origin of Galen's term is unclear. Supposedly the sacrum was the part of an animal offered in sacrifice (since the sacrum is the seat of

581-442: Is swallowed , and moves through the esophagus to the stomach . In the stomach, food is mixed with gastric acids to allow the extraction of nutrients . What is left is called chyme ; this then moves into the small intestine , which absorbs the nutrients and water from the chyme. What remains passes on to the large intestine , where it is dried to form feces ; these are then stored in the rectum until they are expelled through

664-433: Is a common disease in which one or more stones form in the gallbladder or biliary tract . Most people are asymptomatic but if a stone blocks the biliary tract, it causes a gallbladder attack , symptoms may include sudden pain in the upper right abdomen or center of the abdomen. Nausea and vomiting may also occur. Typical treatment is removal of the gallbladder through a procedure called a cholecystectomy . Having gallstones

747-444: Is a risk factor for gallbladder cancer , which although quite uncommon, is rapidly fatal if not diagnosed early. The circulatory system consists of the heart and blood vessels ( arteries , veins and capillaries ). The heart propels the circulation of the blood, which serves as a "transportation system" to transfer oxygen , fuel, nutrients, waste products, immune cells and signaling molecules (i.e. hormones ) from one part of

830-415: Is brought by the ureters from the kidneys down to the bladder . The smooth muscle lining the ureter walls continuously tighten and relax through a process called peristalsis to force urine away from the kidneys and down into the bladder. Small amounts of urine are released into the bladder every 10–15 seconds. The bladder is a hollow balloon shaped organ located in the pelvis . It stores urine until

913-730: Is composed of elements including hydrogen , oxygen , carbon , calcium and phosphorus . These elements reside in trillions of cells and non-cellular components of the body. The adult male body is about 60% total body water content of some 42 litres (9.2 imp gal; 11 US gal). This is made up of about 19 litres (4.2 imp gal; 5.0 US gal) of extracellular fluid including about 3.2 litres (0.70 imp gal; 0.85 US gal) of blood plasma and about 8.4 litres (1.8 imp gal; 2.2 US gal) of interstitial fluid , and about 23 litres (5.1 imp gal; 6.1 US gal) of fluid inside cells. The content, acidity and composition of

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996-419: Is influenced by the distribution of bones, muscle and fat tissue . Human physiology is the study of how the human body functions. This includes the mechanical, physical, bioelectrical , and biochemical functions of humans in good health, from organs to the cells of which they are composed. The human body consists of many interacting systems of organs. These interact to maintain homeostasis , keeping

1079-509: Is mostly responsible for gathering information with sensory neurons and directing body movements with motor neurons . From a functional perspective, the nervous system is again typically divided into two component parts: the somatic nervous system (SNS) and the autonomic nervous system (ANS). The SNS is involved in voluntary functions like speaking and sensory processes . The ANS is involved in involuntary processes, such as digestion and regulating blood pressure . The nervous system

1162-405: Is similar to the circulatory system in terms of both its structure and its most basic function, to carry a body fluid. The musculoskeletal system consists of the human skeleton (which includes bones , ligaments , tendons , joints and cartilage ) and attached muscles . It gives the body basic structure and the ability for movement. In addition to their structural role, the larger bones in

1245-430: Is subject to many different diseases. In epilepsy , abnormal electrical activity in the brain can cause seizures . In multiple sclerosis , the immune system attacks the nerve linings , damaging the nerves' ability to transmit signals. Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig 's disease, is a motor neuron disease which gradually reduces movement in patients. There are also many other diseases of

1328-456: Is that of caudal regression syndrome also known as sacral agenesis . This is characterised by an abnormal underdevelopment in the embryo (occurring by the seventh week) of the lower spine. Sometimes part of the coccyx is absent, or the lower vertebrae can be absent, or on occasion a small part of the spine is missing with no outward sign. Sacral fractures are relatively uncommon; however, they are often associated with neurological deficits. In

1411-426: Is the large triangular orifice of the sacral canal, which is completed by the lamina and spinous process of the first sacral vertebra. The superior articular processes project from it on either side; they are oval, concave, directed backward and medialward, like the superior articular processes of a lumbar vertebra. They are attached to the body of the first sacral vertebra and to each ala, by short thick pedicles; on

1494-425: Is the organ of thought , emotion, memory , and sensory processing ; it serves many aspects of communication and controls various systems and functions. The special senses consist of vision , hearing , taste , and smell . The eyes , ears , tongue , and nose gather information about the body's environment. From a structural perspective, the nervous system is typically subdivided into two component parts:

1577-442: Is the study of the shape and form of the human body. The human body has four limbs (two arms and two legs), a head and a neck , which connect to the torso . The body's shape is determined by a strong skeleton made of bone and cartilage , surrounded by fat ( adipose tissue ), muscle, connective tissue , organs, and other structures. The spine at the back of the skeleton contains the flexible vertebral column , which surrounds

1660-433: Is variable in shape and size. It stores bile before it is released into the small intestine via the common bile duct to help with digestion of fats . It receives bile from the liver via the cystic duct , which connects to the common hepatic duct to form the common bile duct . The gallbladder gets its blood supply from the cystic artery , which in most people, emerges from the right hepatic artery . Gallstones

1743-441: The anus . The endocrine system consists of the principal endocrine glands : the pituitary , thyroid , adrenals , pancreas , parathyroids , and gonads , but nearly all organs and tissues produce specific endocrine hormones as well. The endocrine hormones serve as signals from one body system to another regarding an enormous array of conditions, resulting in variety of changes of function. The immune system consists of

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1826-520: The central nervous system (CNS), composed of the brain and the spinal cord ; and the peripheral nervous system (PNS), composed of the nerves and ganglia outside the brain and spinal cord. The CNS is mostly responsible for organizing motion , processing sensory information , thought, memory, cognition and other such functions. It remains a matter of some debate whether the CNS directly gives rise to consciousness . The peripheral nervous system (PNS)

1909-468: The heart , lungs and liver . Many organs reside within cavities within the body. These cavities include the abdomen (which contains the stomach, for example) and pleura , which contains the lungs. The heart is an organ located in the thoracic cavity between the lungs and slightly to the left. It is surrounded by the pericardium , which holds it in place in the mediastinum and serves to protect it from blunt trauma, infection and help lubricate

1992-441: The kidneys filter the blood through their respective nephrons , removing waste products like urea , creatinine and maintaining the proper balance of electrolytes and turning the waste products into urine by combining them with water from the blood. The kidneys filter about 150 quarts (170 liters) of blood daily, but most of it is returned to the blood stream with only 1-2 quarts (1-2 liters) ending up as urine. The urine

2075-442: The lumbar plexus with the sacral plexus . In the articulated pelvis, the alae are continuous with the iliac fossa . Each ala is slightly concave from side to side, and convex from the back and gives attachment to a few of the fibers of the iliacus muscle . The posterior quarter of the ala represents the transverse process, and its anterior three-quarters the costal process of the first sacral segment. Each ala also serves as part of

2158-411: The multifidus muscle . The floor of the groove is formed by the united laminae of the corresponding vertebrae. The laminae of the fifth sacral vertebra, and sometimes those of the fourth, do not meet at the back, resulting in a fissure known as the sacral hiatus in the posterior wall of the sacral canal . The sacral canal is a continuation of the spinal canal and runs throughout the greater part of

2241-584: The organs of procreation ). Others attribute the adjective ἱερόν to the ancient belief that this specific bone would be indestructible. As the Greek adjective ἱερός may also mean "strong", it has also been suggested that os sacrum is a mistranslation of a term intended to mean "the strong bone". This is supported by the alternative Greek name μέγας σπόνδυλος by the Greeks, translating to "large vertebra", translated into Latin as vertebra magna . In Classical Greek

2324-456: The ovary of a female is penetrated by sperm . The egg then lodges in the uterus , where an embryo and later fetus develop until birth . Growth and development occur after birth, and include both physical and psychological development, influenced by genetic, hormonal, environmental and other factors. Development and growth continue throughout life, through childhood , adolescence , and through adulthood to old age , and are referred to as

2407-644: The public domain from page 106 of the 20th edition of Gray's Anatomy (1918) Human body The human body is the entire structure of a human being . It is composed of many different types of cells that together create tissues and subsequently organs and then organ systems . The external human body consists of a head , hair , neck , torso (which includes the thorax and abdomen ), genitals , arms , hands , legs , and feet . The internal human body includes organs, teeth , bones , muscle , tendons , ligaments , blood vessels and blood , lymphatic vessels and lymph . The study of

2490-407: The sinoatrial node traveling through the atria causing them to pump blood into the ventricles . It then travels to the atrioventricular node , which makes the signal slow down slightly allowing the ventricles to fill with blood before pumping it out and starting the cycle over again. Coronary artery disease is the leading cause of death worldwide , making up 16% of all deaths. It is caused by

2573-400: The spinal cord , which is a collection of nerve fibres connecting the brain to the rest of the body. Nerves connect the spinal cord and brain to the rest of the body. All major bones, muscles, and nerves in the body are named, with the exception of anatomical variations such as sesamoid bones and accessory muscles . Blood vessels carry blood throughout the body, which moves because of

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2656-421: The spleen and bone marrow . The digestive system consists of the mouth including the tongue and teeth , esophagus , stomach , ( gastrointestinal tract , small and large intestines , and rectum ), as well as the liver , pancreas , gallbladder , and salivary glands . It converts food into small, nutritional, non-toxic molecules for distribution and absorption into the body. These molecules take

2739-432: The testicles . The testicle is the gonad , the sex gland that produces the sperm cells . Unlike the egg cells in the female, sperm cells are produced throughout life. Other internal sex organs are the epididymides , vasa deferentia , and some accessory glands . Diseases that affect the reproductive system include polycystic ovary syndrome , a number of disorders of the testicles including testicular torsion , and

2822-427: The uterus , and the cervix . At birth there are about 70,000 immature egg cells that degenerate until at puberty there are around 40,000. No more egg cells are produced. Hormones stimulate the beginning of menstruation, and the ongoing menstrual cycles . The female external sex organs are the vulva ( labia , clitoris , and vestibule ). The male external genitalia include the penis and scrotum that contains

2905-441: The white blood cells , the thymus , lymph nodes and lymph channels, which are also part of the lymphatic system . The immune system provides a mechanism for the body to distinguish its own cells and tissues from outside cells and substances and to neutralize or destroy the latter by using specialized proteins such as antibodies , cytokines , and toll-like receptors , among many others. The integumentary system consists of

2988-534: The S1–S5 vertebrae of a horse will fuse, the S1–S3 of a dog will fuse, and four pelvic vertebrae of a rat will fuse between the lumbar and the caudal vertebrae of its tail. The Stegosaurus dinosaur had a greatly enlarged neural canal in the sacrum, characterized as a " posterior brain case ". The sacrum is a complex structure providing support for the spine and accommodation for the spinal nerves . It also articulates with

3071-436: The ages of 9 and 13 and is characterized by ovulation and menstruation ; the growth of secondary sex characteristics, such as growth of pubic and underarm hair , breast , uterine and vaginal growth, widening hips and increased height and weight, also occur during puberty. Male puberty sees the further development of the penis and testicles . The female inner sex organs are the two ovaries, their fallopian tubes ,

3154-435: The air and excretes carbon dioxide and water back into the air. First, air is pulled through the trachea into the lungs by the diaphragm pushing down, which creates a vacuum . Air is briefly stored inside small sacs known as alveoli (sing.: alveolus) before being expelled from the lungs when the diaphragm contracts again. Each alveolus is surrounded by capillaries carrying deoxygenated blood, which absorbs oxygen out of

3237-420: The air and into the bloodstream . For the respiratory system to function properly, there need to be as few impediments as possible to the movement of air within the lungs. Inflammation of the lungs and excess mucus are common sources of breathing difficulties. In asthma , the respiratory system is persistently inflamed, causing wheezing or shortness of breath . Pneumonia occurs through infection of

3320-468: The alae (wings), and articulate with the ilium at the L-shaped sacroiliac joints . The upper part of the sacrum connects with the last lumbar vertebra (L5), and its lower part with the coccyx (tailbone) via the sacral and coccygeal cornua. The sacrum has three different surfaces which are shaped to accommodate surrounding pelvic structures. Overall, it is concave (curved upon itself). The base of

3403-400: The alveoli, and may be caused by tuberculosis . Emphysema , commonly a result of smoking , is caused by damage to connections between the alveoli. The urinary system consists of the two kidneys , two ureters , bladder , and urethra . It removes waste materials from the blood through urine, which carries a variety of waste molecules and excess ions and water out of the body. First,

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3486-432: The back and middle, and articulate with the facets on the inferior processes of the fifth lumbar vertebra. The tubercles of the inferior articular processes of the fifth sacral vertebra, known as the sacral cornua, are projected downward and are connected to the cornua of the coccyx. At the side of the articular processes are the four posterior sacral foramina ; they are smaller in size and less regular in form than those at

3569-406: The beating of the heart . Venules and veins collect blood low in oxygen from tissues throughout the body. These collect in progressively larger veins until they reach the body's two largest veins, the superior and inferior vena cava , which drain blood into the right side of the heart. From here, the blood is pumped into the lungs where it receives oxygen and drains back into the left side of

3652-402: The bodies of the next bones get progressively smaller, are flattened from the back, and curved to shape themselves to the sacrum, being concave in front and convex behind. At each end of the transverse ridges, are the four anterior sacral foramina , diminishing in size in line with the smaller vertebral bodies. The foramina give exit to the anterior divisions of the sacral nerves and entrance to

3735-427: The body contain bone marrow , the site of production of blood cells. Also, all bones are major storage sites for calcium and phosphate . This system can be split up into the muscular system and the skeletal system . The nervous system consists of the body's neurons and glial cells, which together form the nerves , ganglia and gray matter , which in turn form the brain and related structures. The brain

3818-423: The body in a stable state with safe levels of substances such as sugar and oxygen in the blood. Each system contributes to homeostasis, of itself, other systems, and the entire body. Some combined systems are referred to by joint names. For example, the nervous system and the endocrine system operate together as the neuroendocrine system . The nervous system receives information from the body, and transmits this to

3901-441: The body to another. Paths of blood circulation within the human body can be divided into two circuits: the pulmonary circuit , which pumps blood to the lungs to receive oxygen and leave carbon dioxide , and the systemic circuit, which carries blood from the heart off to the rest of the body. The blood consists of fluid that carries cells in the circulation, including some that move from tissue to blood vessels and back, as well as

3984-481: The bone was known as κλόνις (Latinized clonis ); this term is cognate to Latin clunis "buttock", Sanskrit śróṇis "haunch" and Lithuanian šlaunis "hip, thigh". The Latin word is found in the alternative Latin name of the sacrum, ossa clunium , as it were "bones of the buttocks". Due to the fact that the os sacrum is broad and thick at its upper end, the sacrum is alternatively called os latum , "broad bone". [REDACTED] This article incorporates text in

4067-424: The border of the pelvic brim . The alae also form the base of the lumbosacral triangle. The iliolumbar ligament and lumbosacral ligaments are attached to the ala. In the middle of the base is a large oval articular surface, the upper surface of the body of the first sacral vertebra, which is connected with the under surface of the body of the last lumbar vertebra by an intervertebral fibrocartilage . Behind this

4150-412: The brain signals it to relax the urinary sphincter and release the urine into the urethra starting urination . A normal bladder can hold up to 16 ounces (half a liter) for 3–5 hours comfortably. Numerous diseases affect the urinary system including kidney stones , which are formed when materials in the urine concentrate enough to form a solid mass, urinary tract infections , which are infections of

4233-463: The brain via nerve impulses and neurotransmitters . At the same time, the endocrine system releases hormones, such as to help regulate blood pressure and volume. Together, these systems regulate the internal environment of the body, maintaining blood flow, posture, energy supply, temperature, and acid balance ( pH ). Development of the human body is the process of growth to maturity. The process begins with fertilisation, where an egg released from

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4316-481: The buildup of plaque in the coronary arteries supplying the heart, eventually the arteries may become so narrow that not enough blood is able to reach the myocardium , a condition known as myocardial infarction or heart attack , this can cause heart failure or cardiac arrest and eventually death. Risk factors for coronary artery disease include obesity , smoking , high cholesterol , high blood pressure , lack of exercise and diabetes . Cancer can affect

4399-412: The cell numbers of all the organs of the body and cell types . The skin of the body is also host to billions of commensal organisms as well as immune cells. Not all parts of the body are made from cells. Cells sit in an extracellular matrix that consists of proteins such as collagen , surrounded by extracellular fluids. Cells in the body function because of DNA . DNA sits within the nucleus of

4482-422: The coccyx, and this transmits the anterior division of the fifth sacral nerve. The thin lower half of the lateral surface gives attachment to the sacrotuberous and sacrospinous ligaments , to some fibers of the gluteus maximus at the back and to the coccygeus in the front. The sacrum articulates with four bones: Rotation of the sacrum superiorly and anteriorly whilst the coccyx moves posteriorly relative to

4565-432: The covering of the body (the skin ), including hair and nails as well as other functionally important structures such as the sweat glands and sebaceous glands . The skin provides containment, structure, and protection for other organs, and serves as a major sensory interface with the outside world. The lymphatic system extracts, transports and metabolizes lymph, the fluid found in between cells. The lymphatic system

4648-458: The form of proteins (which are broken down into amino acids ), fats , vitamins and minerals (the last of which are mainly ionic rather than molecular). After being swallowed , food moves through the gastrointestinal tract by means of peristalsis : the systematic expansion and contraction of muscles to push food from one area to the next. Digestion begins in the mouth , which chews food into smaller pieces for easier digestion. Then it

4731-405: The fresh state, are filled by the intervertebral discs . The dorsal surface of the sacrum is convex and narrower than the pelvic surface. In the middle line is the median sacral crest , surmounted by three or four tubercles —the rudimentary spinous processes of the upper three or four sacral vertebrae. On either side of the median sacral crest is a shallow sacral groove, which gives origin to

4814-404: The front, and transmit the posterior divisions of the sacral nerves. On the side of the posterior sacral foramina is a series of tubercles, the transverse processes of the sacral vertebrae, and these form the lateral sacral crest . The transverse tubercles of the first sacral vertebra are large and very distinct; they, together with the transverse tubercles of the second vertebra, give attachment to

4897-403: The heart , though it is exceedingly rare and has usually metastasized from another part of the body such as the lungs or breasts . This is because the heart cells quickly stop dividing and all growth occurs through size increase rather than cell division . The gallbladder is a hollow pear-shaped organ located posterior to the inferior middle part of the right lobe of the liver . It

4980-434: The heart. From here, it is pumped into the body's largest artery , the aorta , and then progressively smaller arteries and arterioles until it reaches tissue. Here, blood passes from small arteries into capillaries , then small veins and the process begins again. Blood carries oxygen , waste products, and hormones from one place in the body to another. Blood is filtered at the kidneys and liver . The body consists of

5063-421: The hip bones. The sacrum has a base, an apex, and three surfaces – a pelvic, dorsal and a lateral surface. The base of the sacrum , which is broad and expanded, is directed upward and forward. On either side of the base is a large projection known as an ala of sacrum and these alae (wings) articulate with the sacroiliac joints . The alae support the psoas major muscles and the lumbosacral trunk which connects

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5146-428: The horizontal parts of the posterior sacroiliac ligaments; those of the third vertebra give attachment to the oblique fasciculi of the posterior sacroiliac ligaments; and those of the fourth and fifth to the sacrotuberous ligaments. The lateral surface of the sacrum is broad above, but narrows into a thin edge below. The upper half presents in front an ear-shaped surface, the auricular surface, covered with cartilage in

5229-405: The horizontal plane that provides a useful marker for a sling implant procedure. The pelvic surface of the sacrum is concave from the top, and curved slightly from side to side. Its middle part is crossed by four transverse ridges, which correspond to the original planes of separation between the five sacral vertebrae. The body of the first segment is large and has the form of a lumbar vertebra;

5312-500: The human body includes anatomy , physiology , histology and embryology . The body varies anatomically in known ways. Physiology focuses on the systems and organs of the human body and their functions. Many systems and mechanisms interact in order to maintain homeostasis , with safe levels of substances such as sugar , iron , and oxygen in the blood. The body is studied by health professionals , physiologists, anatomists, and artists to assist them in their work. The human body

5395-459: The ilium is sometimes called "nutation" (from the Latin term nutatio which means "nodding") and the reverse, postero-inferior motion of the sacrum relative to the ilium whilst the coccyx moves anteriorly, "counter-nutation". In upright vertebrates, the sacrum is capable of slight independent movement along the sagittal plane . On bending backward the top (base) of the sacrum moves forward relative to

5478-419: The ilium; on bending forward the top moves back. The sacrum refers to all of the parts combined. Its parts are called sacral vertebrae when referred individually. In some cases, the sacrum will consist of six pieces or be reduced in number to four. The bodies of the first and second vertebrae may fail to unite. The somites that give rise to the vertebral column begin to develop from head to tail along

5561-411: The immature state, for articulation with the ilium. Behind it is a rough surface, the sacral tuberosity , on which are three deep and uneven impressions, for the attachment of the posterior sacroiliac ligament. The lower half is thin, and ends in a projection called the inferior lateral angle. Medial to this angle is a notch, which is converted into a foramen by the transverse process of the first piece of

5644-439: The lateral sacral arteries. Each part at the sides of the foramina is traversed by four broad, shallow grooves, which lodge the anterior divisions of the sacral nerves. They are separated by prominent ridges of bone which give origin to the piriformis muscle . If a sagittal section be made through the center of the sacrum, the bodies are seen to be united at their circumferences by bone, wide intervals being left centrally, which, in

5727-435: The length of the notochord. At day 20 of embryogenesis , the first four pairs of somites appear in the future occipital bone region. Developing at the rate of three or four a day, the next eight pairs form in the cervical region to develop into the cervical vertebrae; the next twelve pairs will form the thoracic vertebrae; the next five pairs the lumbar vertebrae and by about day 29, the sacral somites will appear to develop into

5810-468: The lumbar and some caudal and thoracic vertebrae to form a single structure called the synsacrum . In the frog , the ilium is elongated and forms a mobile joint with the sacrum that acts as an additional limb to give more power to its leaps. English sacrum was introduced as a technical term in anatomy in the mid-18th century, as a shortening of the Late Latin name os sacrum "sacred bone", itself

5893-421: The lungs, to column-like cells that line the stomach . Endothelial cells are cells that line internal cavities including blood vessels and glands. Lining cells regulate what can and cannot pass through them, protect internal structures, and function as sensory surfaces. Organs , structured collections of cells with a specific function, mostly sit within the body, with the exception of skin . Examples include

5976-415: The movement of the heart via pericardial fluid . The heart works by pumping blood around the body allowing oxygen , nutrients , waste , hormones and white blood cells to be transported. The heart is composed of two atria and two ventricles . The primary purpose of the atria is to allow uninterrupted venous blood flow to the heart during ventricular systole . This allows enough blood to get into

6059-407: The nervous system. The purpose of the reproductive system is to reproduce and nurture the growth of offspring. The functions include the production of germ cells and hormones. The sex organs of the male reproductive system and the female reproductive system develops and mature at puberty . These systems include the internal and external genitalia . Female puberty generally occurs between

6142-419: The presence of neurological signs, they are mostly treated with surgical fixation . The sacrum is one of the main sites for the development of the sarcomas known as chordomas that are derived from the remnants of the embryonic notochord . In dogs , the sacrum is formed by three fused vertebrae. The sacrum in the horse is made up of five fused vertebrae. In birds , the sacral vertebrae are fused with

6225-452: The process of aging . Pelvic inlet Its position and orientation relative to the skeleton of the pelvis is anatomically defined by its edge, the pelvic brim . The pelvic brim is an approximately apple-shaped line passing through the prominence of the sacrum , the arcuate and pectineal lines , and the upper margin of the pubic symphysis . Occasionally, the terms pelvic inlet and pelvic brim are used interchangeably. The edge of

6308-431: The sacral vertebrae; finally on day 30, the last three pairs will form the coccyx. The congenital disorder , spina bifida , occurs as a result of a defective embryonic neural tube , characterised by the incomplete closure of vertebral arch or of the incomplete closure of the surface of the vertebral canal. The most common sites for spina bifida malformations are the lumbar and sacral areas. Another congenital disorder

6391-464: The sacrum , the broadest and uppermost part, is tilted forward as the sacral promontory internally. The central part is curved outward toward the posterior , allowing greater room for the pelvic cavity . In all other quadrupedal vertebrates , the pelvic vertebrae undergo a similar developmental process to form a sacrum in the adult, even while the bony tail (caudal) vertebrae remain unfused. The number of sacral vertebrae varies slightly. For instance,

6474-465: The sacrum. Above the sacral hiatus, it is triangular in form. The canal lodges the sacral nerves , via the anterior and posterior sacral foramina. On the lateral aspect of the sacral groove is a linear series of tubercles produced by the fusion of the articular processes which together form the indistinct medial sacral crest . The articular processes of the first sacral vertebra are large and oval-shaped. Their facets are concave from side to side, face to

6557-400: The two pieces of sacrum. Normally, it is greater than 60 degrees. A sacral angle of lesser degree suggests funneling of the pelvis. The sacral promontory marks part of the border of the pelvic inlet , and comprises the iliopectineal line and the linea terminalis . The sacral promontory articulates with the last lumbar vertebra to form the sacrovertebral angle , an angle of 30 degrees from

6640-418: The upper surface of each pedicle is a vertebral notch, which forms the lower part of the foramen between the last lumbar and first sacral vertebrae. The apex is directed downward and presents an oval facet for articulation with the coccyx . The sacral canal as a continuation of the vertebral canal runs throughout the greater part of the sacrum. The sacral angle is the angle formed by the true conjugate with

6723-405: The urinary tract and can cause pain when urinating, frequent urination and even death if left untreated. Renal failure occurs when the kidneys fail to adequately filter waste from the blood and can lead to death if not treated with dialysis or kidney transplantation . Cancer can affect the bladder , kidneys , urethra and ureters , with the latter two being far more rare. Human anatomy

6806-417: The ventricles during atrial systole . Consequently, the atria allows a cardiac output roughly 75% greater than would be possible without them. The purpose of the ventricles is to pump blood to the lungs through the right ventricle and to the rest of the body through the left ventricle. The heart has an electrical conduction system to control the contraction and relaxation of the muscles. It starts in

6889-401: The water inside and outside cells is carefully maintained. The main electrolytes in body water outside cells are sodium and chloride , whereas within cells it is potassium and other phosphates . The body contains trillions of cells , the fundamental unit of life. At maturity, there are roughly 30 trillion cells, and 38 trillion bacteria in the body, an estimate arrived at by totaling

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