The corpora of the urethra is the body of the urethral tube. The urethra passes from the base of the bladder, through the corpus cavernosa of the penis, and terminating in the urethral meatus at the apex of the glans of the penis. The urethra in the male body carries both urine and semen to the exterior of the body. Research Corpora
The penis supports the urethra as it passes from the seminal vesicles, through the corpora cavernosa, to the meatus at the glans of the penis. The corpora cavernosa are made of spongy tissue which fill with blood during sexual arousal. As the blood fills these tissues, the penis begins to expand and become firm, and this condition is known as an erection. The erection facilitates the ejaculational transport of the semen to the female's vagina. Research Corpora Cavernosa
The ear is the organ used for hearing. It converts sound into electrical impulses that are fed to the brain. The external ear is composed of the auricle (the pinna), and the auditory canal (the meatus auditorius externus). The Pinna or auricle surrounds the entrance to the auditory canal. It consists of cartilage covered by skin, with small muscles connecting it to the scalp. At the base of the ear is a fleshy lobe. The meatus auditorius is a canal about three centimeters long in the adult, partly bony and partly cartilaginous, leading from the pinna of the ear to the drum. The lining cells secrete the waxy substance found in the canal. In young children the canal is much shorter. The ear drum (tympanic membrane) is a thin oval-shaped membrane, inserted into a groove around the auditory canal. Normally it is white, glistening and somewhat transparent, so that some of the structures of the middle ear are partly visible when viewed through an auroscope. It separates the auditory canal from the middle ear.
The Tympanum or middle ear is a cavity within the temporal bone. It contains several important structures, including three small bones which connect the drum with the internal ear; they are the malleus or hammer, the incus or anvil, and the stapes or stirrupbone. They transmit the vibrations of sound waves to the inner ear. The Eustachian Tube is a channel of communication between the tympanum and the upper part of the pharynx. It admits air from the throat to the tympanum and so maintains an equal pressure on both sides of the drum. The Labyrinth or internal ear is a series of chambers through the petrous bone, comprising the vestibule, a three-cornered cavity within the tympanum; the semicircular canals communicating with the vestibule; and the cochlea, which makes two and a half turns around an axis called the modiolus. The human ear is capable of detecting sounds in the frequency range 20 hz to 20 khz, approximately. Research Ear
The female reproductive system is responsible for generating the ovum, or egg, for storing the fertilized ovum, and nourishing the gestating embryo and fetus. The chief organs include the ovaries, the uterus, vagina, and the fallopian tubes. External (vulvar) organs include the labia majora, the labia minora, the mons pubis, the clitoris, the vestibule, and the greater vestibular cleft. The ovum, or egg, contains the female's contribution to the genetic make-up of the new child, and is generated in the ovaries. The newly generated ovum is passed through the fimbriated extremity of a fallopian tube, into the fallopian tube and there is fertilized by a spermatozoon (a sperm cell). During sexual arousal, a fluid created by the male's seminal vesicles and the prostate gland combines with the sperm cells to create semen, which is carried through the urethra and out of the opening, or meatus, in the end of the erect penis.
When the semen is deposited in the female vagina, the spermatozoa swims through the uterus to the fallopian tube, where it fertilizes the ovum, or egg. The fertilized egg travels down the fallopian tube within the next three days and becomes attached to the wall of the uterus (womb). There, during pregnancy, the fertilized egg will be nourished and will develop into the embryo and, later, the fetus. Once fully developed (after about 9 months), muscular contractions (labor) will push the fetus out of the womb. Research Female Reproductive System
The glans of the penis is the enlarged tip, or head, of the penis. In its apex is the vertical meatus of the urethra. The glans is covered by a loose fold of skin, called the foreskin or prepuce, which is often removed from infants for religious reasons. Research Glans of the Penis
The male reproductive system is responsible for generating, storing, and transporting the genetic material contained in the sperm cells, or spermatozoa. The chief organs include the testicles (or testes), the epididymides, the vas deferens, the ejaculatory duct, the urethra, and the penis. Auxiliary organs include the bulbourethral (Cowper's) glands, the prostate gland, and the seminal vesicles. Spermatozoa (sperm cells) contain the chromosomes which will combine with those of the ovum, or egg (produced by the female reproductive system), to form the embryo of a new human. These spermatozoa are generated within the testicles and stored within the epididymides. During sexual arousal, a fluid created by the seminal vesicles and the prostate gland combines with the sperm cells to create semen, which is carried through the urethra and out of the opening, or meatus, in the end of the erect penis. When the semen is deposited in the female vagina, the spermatozoa swim through the uterus to the fallopian tube, where one, or more, may fertilize an egg, or ovum. Research Male Reproductive System
The mandible (lower jawbone) is the only movable bone in the skull. It mounts the teeth and provides structure and protective support for the oral cavity. The mandible is articulated in ball-and- socket fashion at the condylar process. The caput of this process fits into the mandibular fossa of the temporal bone, just in front of the external acousticmeatus, and nestled neatly under and slightly to the back of the articular tubercle of the zygomatic process. To the front of this atriculation is the protrusion called the coronoid process, which fits snugly beneath the zygomatic arch when the mouth is closed. A curved depression lies between the caput and the coronoid process on this upper section of the mandible. The mandibular angles are the lower, back corners of the jawbone, while the ramus is the section on each side of the mandible between the caput of the condylar process and the angle. In the front of the mandible are the mental tubercles and protuberances which define the chin. On each side of the chin is an opening
called a mental foramen. Research Mandible
The meatus are groove-like passages between the turbinates (nasal conchae) in the nasal cavity. Of the three passages (inferior meatus, middle meatus, and superior meatus) the inferior meatus is the largest and the superior meatus is the smallest. The passages are lined with mucousmembrane. Nerve endings responsible for the sense of smell are located in the nasal musosa. Research Meatus
The petrosquamous fissure, or suture, denotes the margins of the petrous part of the temporal bone and the squamous part. The squamous part is the anterior section, which comprises most of the glenoid fossa. The petrous part is the posterior section, which forms the rear portion of the glenoid fossa and the frontal wall of the tympanum and external auditory meatus. Research Petrosquamous Fissure
The skull is one of the principle groups of bones in the human anatomy. The skull consists of twenty-six bones: eight bones form the skull, which houses the brain and ear ossicles, plus fourteen facial bones, which form the front of the face, jaw, nose, orbits, and the roof of the mouth, three more bones make up the inner ear ossicles, and one more, the hyoid bone, is in the neck and is attached to the temporal bone by ligaments and anchors the tongue. The skull also contains a dental arcade of teeth, which are technically not bones, though they do share some of the compositional characteristics of bonetissue. Children may grow twenty deciduousteeth, which will eventually fall out and be replaced by the permanent teeth.
The bones of the skull include the frontal bone, the occipital bone, two parietal bones, and two temporal bones. The lower rearmost part of each temporal bone is called the mastoid process, but because it is separated from the temporal bone, proper, by a suture, it is often considered a separate bone. The sphenoid bone forms the central base of the skull and spans the skull from side to side, the greater wings forming side plates of the skull. The sections of the ethmoid bone are positioned between the orbits, forming the walls and roof of the nasal cavity, while the three middle ear ossicles (stapes, malleus, and incus) are located within the temporal bones on each side of the skull. The U-shaped hyoid bone is found in the neck, and is attached by ligaments to the temporal bones. In the face, the two maxillary bones form much of the orbits, nose, upper jaw and roof of the mouth, while the zygomatic bones form the cheeks. The lachrymal bones are located on the inner sides of the orbits and are attached to the ethmoid bone and maxillary bones. Within the nasal cavity, the vomer is located in the low center and forms the thin flat bone of the nasalseptum, while two inferior urbinates form the lower sides of the cavity and two palate bones form the floor of the nasal cavity as well as the roof of the mouth.
The mandible is the only movable part of the skull, forming the lower jaw and mounting the teeth. The bones of the skull, with the exception of the mandible, are held together by very thin sutures, or seams, in which the periosteum of the individual bones interweave with each other, and are cemented by a fibrous, connective tissue. In the newborn, these sutures are not yet developed, with the bones being attached by cartilage which ossifies over time as the bones of the skull fuse together. The most evident external sutures of the skull include the coronal suture, joining the frontal bone and parietal bone, the sagittal suture, joining the parietal bones to each other, the lambdoid suture, joining the occipital and parietal bones, the squamous suture, joining the temporal and sphenoid bones to the parietal bone on each side of the skull.
The pterion is the short segment of the suture joining the squamous and parietal bones. The bones of the skull also feature a number of sinuses and foramina. Four pairs of sinuses flank the nasal cavity. Two are found in the maxillary bone, and are called maxillary sinuses. The sphenoid bone forms two paranasal sinuses called the sphenoids, and the ethmoid bone forms the two paranasal sinuses called ethmoids. Additionally, the frontal sinuses are located in the frontal bone just behind the roof of each orbit. The foramen magnum is a large, round opening in the base of the skull which admits the spinal cord, while at the base of each temporal bone is the external auditory meatus, which serve as the auditory canals. Just above each orbit in the frontal bone is a small notch or hole, called a supraorbital foramen, and just below each orbit, in the maxillary bone, is an infraorbital foramen. Two more openings, one on each side of the skull, can be found in the frontal processes of the zygomatic bones, and are called zygomatofacial foramina.
On each side of the mandible, just below the lower canines, are the mental foramina. These facial foramina serve to admit blood vessels and nerves through and into the bone. The teeth are mounted in the maxillary bone and the mandible, and are brought together for chewing by the hinge-like motion of the mandible. An average adult will have thirty-two teeth, evenly arrayed on the maxilla and mandible. Research Skull
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Corpora
