Oral histology

• Enamel is the hard outer layer of teeth that provides protection and aids in grinding food.
• Chromosomes are thread-like structures composed of DNA and other proteins, found in human cells normally have 46 chromosomes which can be arranged in 23 pairs.
• 22 chromosomes are alike in male and female, they are called autosomes.
• The 23rd pair of chromosomes are the sex chromosomes, which are not the same in males and females, they are called sex chromosomes.
• Gametes are produced in the ovary for females and in the testes for males, they are homogametic as they contain only the X sex chromosomes.
• Fertilization is the fusion of male and female germ cells, forming a zygote which commences the formation of a new individual.
• The germinal phase of prenatal development begins at fertilization and spans the first 4 weeks of development, involving cellular proliferation and migration with some differentiation of cell populations.
• The embryonic phase of prenatal development involves cell differentiation.
• The fetal phase of prenatal development begins at the eighth week of pregnancy.
• The morula is a solid mass of blastomeres, formed during the germinal phase of prenatal development, it is an egg cell mass and has a short duration only (3 - 4 days post fertilization).
• The blastula is a circular, hollow, cluster of cells produced at the same time as an embryo is developing, formed during the germinal phase of prenatal development.
• The embryonic phase of prenatal development begins at the third week of development, involving cell differentiation.
• Gastrulation is a period during the third week of development where the germ layers form, cells in the blastula rearrange themselves spatially to form three layers of cells: Ectoderm, Mesoderm, Endoderm.
• The Ectoderm layer of the embryo is responsible for the skin and the nervous system.
• The Mesoderm layer of the embryo is responsible for bone, muscle, and connective tissue.
• The Endoderm layer of the embryo is responsible for the linings of the digestive and respiratory system, and forms organs such as the liver and pancreas.
• Neural Crest Cells are multipotent cells that form a band of neuroectodermal cells that lie dorsolateral to the developing spinal cord, where they separate into a cluster of cells.
• Ectomesenchyme consists of neural crest cells and mesodermal cells.
• The Stomodeum is an ectoderm-lined invagination in between the maxillary and mandibular processes of the first branchial arch.
• Rathke’s pouch is a diverticulum that arises from the roof of the stomodeum and grows toward the brain, eventually forming the portion of the pituitary gland known as the adenohypophysis.
• Branchial Arches are a series of 5 bar-like ridges that appear on the ventrolateral surface of the head and neck region as the result of the proliferative activity of neural crest cells.
• The ectoderm between the arches forms clefts (grooves) called Branchial Clefts (pharyngeal grooves).
• In each arch, a skeletal element, artery, muscles supplied by the nerve of that arch is formed.
• Dermoid Cyst contains hair, sebaceous and sweat glands and is common in the floor of the mouth.
• Lack of fusion of the distal tongue buds is a condition where the distal tongue buds do not fuse.
• Nasolabial Cyst is a developmental cyst of soft tissue of the anterior mucobuccal fold.
• Lymphoepithelial Cyst is most commonly seen in the floor of the mouth and on the lateral aspect of the neck.
• Stafne Bone Cyst is an asymptomatic radiolucency near the angle of the mandible below the mandibular canal.
• Persistence of the tuberculum impar is a condition where the tuberculum impar remains after the fusion of the distal tongue buds.
• Nasopalatine Duct Cyst is an intraosseous developmental cyst of the midline of the anterior palate.
• Bifid tongue is a condition where the uvula is split into two parts.
• Asymptomatic means no treatment is necessary for a condition.
• Meckel’s cartilage is characterized by being a model for the mandible but not participating in the formation of any part of the mandible.
• Human Facial Development involves the formation of facial prominences such as the Frontonasal which forms the forehead and nose, and the Maxillary which forms the upper cheek regions and most of the upper lip.
• Human Facial Development also involves the formation of the Tongue Tuberculum Impair, a rounded swelling; median tongue bud, resulting from the fusion of tuberculum impar, the lingual swellings (first arch), and cranial part of the hypobranchial eminence (third and fourth arches).
• The primary palate is formed by the premaxilla of the frontonasal process.
• Treacher Collins’ Syndrome, also known as mandibulofacial dysostosis, is an inherited disorder that results from the action of a dominant gene and may be almost as common as hemifacial microsomia.
• The tongue develops a copula from the second arch and hypobranchial eminence from the 3 rd arch in the posterior 1/3 of the tongue.
• The tongue develops two distal tongue buds (lateral lingual swellings) on each side of the median tongue bud in the anterior 2/3 of the tongue.
• Hemifacial microsomia is used to describe malformations involving underdevelopment and other abnormalities of the temporomandibular joint, the external and middle ear, and other structures in this region, such as the parotid gland and muscles of mastication.