Dental Anatomy. Chapter 8. Test 4 Flashcards
What are the three periods of prenatal periods?
germinal (preimplantation period) - the first 2 weeks, embryonic - beginning of the second week to the end of the eighth week, and fetal - begins with the ninth week and lasts until birth.
Which period of prenatal development is the most critical, and why?
The embryonic period is the most critical time because, during these weeks, development begins in all major structures of the body. Because all the organ systems are formed during the embryonic period, the fetus is less vulnerable than the embryo to malformations caused by radiation, viruses, and drugs.
What are the three primary embryonic layers?
During the third week of development, the cells of the embryo form the three primary embryonic layers: ectoderm (outer layer), mesoderm (middle layer), and endoderm (inner layer).
Which branchial arch forms the bones, muscles, nerves of the face, and lover lip?
first branchial arch (“Meckel’s cartilage” or mandibular arch).
Note: by the end of the fifth embryonic week, four bulges that are on top of each other form the branchial arches.
Which branchial arch forms the side and front of the neck.
second branchial arch (hyoid arch). Also it forms the styloid process, stapes of the ear, stylohyoid ligament, part of the hyoid bone, and more.
What are the three stages of palate formation?
The palate is formed in three consecutive stages:
a) Formation of the primary palate
b) Formation of the secondary palate
c) Fusion of the palate (Fusion begins from the 5th week and is completed within the 12th week). The fusion makes a Y-shaped pattern in the roof of the mouth.
the palate is formed during both the embryonic and fetal periods.
The process of formation of the primary and secondary palate begins in the fifth week of prenatal development.
When does the development of the human face occur?
between the fifth and eight week.
What are the four stages of tooth formation in utero?
Tooth formation (or odontogenesis) begins with the primary teeth approximately at the 5-week embryonic period, and the succedaneous (permanent) teeth around 10 week.
There are 4 stages taking place in-utero (and there are plus the final two stages until eruption):
a. Initiation stage starts with the formation of the dental lamina, which is a thickened band of oral epithelium that follows the curve of each dental arch.
b. Bud stage is the beginning development of each tooth.
c. Cap stage, the cells of the tooth grow and increase in number. This growth causes changes in size and proportion of the tooth, and the tooth bud changes into a hollow, cap-like shape.
d. Bell stage, the cells differentiate and become more specialized.
What are the two major factors that can adversely influence dental development?
a. Genetic factors also referred to as heredity in transmitted from parents to their children through their genes and can play a contributing role in some oral conditions.
b. Congenital factors are those present at birth and caused by a genetic mutation or external source.
The mother’s dental health is also of concern. Toxins from a dental infection may be dangerous to both mother and child (e.g., toxins from periodontal disease in the mother are linked to low birth weight in the infant).
What is the process of adding bone?
Deposition is the process of “lying down” or adding new bone. Osteoblasts are the cells that are responsible for new bone formation.
What is the process of the body removing bone?
Resorption occurs when the body removes bone. Osteoclasts are the cells responsible for this process, in which bone cells are resorbed (taken away) by the body.
What is the name of the process by which teeth move into the oral cavity?
Eruption is the movement of the tooth into its functional position in the oral cavity.
Which teeth are the most affected by ankylosis?
Ankylosed teeth are primary teeth in which the bone has fused to cementum and dentin. This prevents exfoliation of the deciduous tooth and eruption of the underlying permanent tooth. Primary molars are most often affected by ankylosis.
What is the difference between the anatomical crown and the clinical crown?
The anatomical crown is the portion of the tooth that is covered with enamel. The size of the anatomical crown remains constant throughout the life of the tooth, regardless of the position of the gingiva.
The clinical crown is the portion of the tooth that is visible in the mouth. The clinical crown varies in length during the life cycle of the tooth depending on the level of the gingiva.
Where is the CEJ?
CEJ – cementoenamel junction. The CEJ is the external line at the neck or cervix of the tooth where the enamel of the crown and the cementum of the root usually meet.
What is the hardest substance in the human body?
Enamel covers the anatomical crown of the tooth and is the hardest material in the body.
How does dentin transmit sensations of pain?
Dentin is penetrated through its entire thickness by microscopic canals called dentinal tubules. Each dentinal tubule contains a dentinal fiber. These fibers, which terminate in a branching network at the junction with the enamel or cementum, transmit pain stimuli and make dentin an excellent thermal conductor.
What are the three types of dentin?
a. Primary dentin, which is formed before eruption, and form the bulk of the tooth.
b. Secondary dentin begins formation after eruption and continues at a very slow rate throughout the life of the tooth resulting in gradual narrowing of the pulp chamber with age.
c. Tertiary dentin also known as reparative dentin, forms in response to irritation and appears as a localized deposit on the wall of the pulp chamber.
What are the two types of cementum?
Primary cementum is formed outward from the CEJ for the full length of the root, as the root develops.
Secondary cementum continues to form on the apical half of the root, after the tooth has reached functional occlusion.
What type of tissue makes up the pulp?
The pulp of a tooth is primarily made up of connective tissue (that consists of cell, intercellular substance, and tissue fluid). It also contains nerves, and blood vessels.
What cells form the intercellular substance of the pulp?
Fibroblasts, a type of cell present in connective tissue, are responsible for the formation of the intercellular substance of the pulp.
What are the functions of osteoblasts and osteoclasts?
Osteoblasts are cells that are responsible for the formation of the alveolar bone. The alveolar bone (also refereed to as the alveolar process) is a thick ridge of bone that contains the tooth socket that hold the teeth.
Osteoclasts are cells that are responsible for resorption and remodeling of the bone (alveolar bone).
Give the five periodontal fiber subgroups.
a. Alveolar crest fibers. Their primary function to retain the tooth in the socket and to oppose lateral forces.
b. Horizontal fibers – to restrain lateral tooth movement.
c. Oblique fibers – to resist forces placed on the long axis of the tooth.
d. Apical fibers – to prevent the tooth from tipping, resist luxation (twisting), and protect blood, lymph, and nerve supplies.
e. Interradicular fibers (found only in multirooted teeth) – to enhance resistance to tipping and twisting.
List the three types of oral mucosa and provide an example of each.
Lining mucosa. It covers the inside of the cheeks, vestibule, lips, soft palate, and ventral surface (underside) of the tongue. Soft, moist, and ability to stretch. Acting as a cushion for underlying structures.
Masticatory mucosa. It includes the attached gingiva, hard palate, and dorsum (upper surface) of the tongue. Rubbery surface and resiliency.
Specialized mucosa. It present on the top surface (dorsal surface0 of the tongue and present in the form of lingual papillae.
What is Embryology
Embryology is the study of prenatal development in the stages before birth
What is histology?
Histology is the study of the structure and function of the tissues on a microscopic level. This includes the tissues and structures of the oral mucosa, which surrounds the teeth and lines the mouth.
fertilization
Pregnancy begins with conception, also known as fertilization.
Occurs when sperm penetrates and fertilizes ovum.
Birth occurs, on average, 38 weeks after conception (which is assumed to have occurred 2 weeks after the LMP), or 40 weeks after the beginning of the last menstrual period (LMP).
For general descriptive purposes, this is divided into three trimesters of 3 months each.
In embryology, developmental age is based on the date of conception, which is assumed to have occurred 2 weeks after the LMP.
Characteristics of Preimplantation Period
Preimplantation period – 1st week
an ovum (egg) penetrated by a sperm and changes the outer coating of the egg so that no other sperm can enter.
This union forms a fertilized egg, called zygote.
The chromosomes within the sperm and egg will determine the growth and development.
The process of joining of both parents’ chromosomes is called meiosis, which ensures that the embryo will have the correct number of chromosomes.
Lack of chromosomes can lead to developmental disorders.
Characteristics of Embryonic Period
From the 3rd week to 8th week
Cells:
proliferate - increase in number.
differentiate - changes into tissues and organs.
integrate - form systems.
Characteristics of Fetal Period
9th week to birth.
Body systems continue to develop and mature.
The fetus has distinguishable ears, arms, hands, legs, and feet.
Is a period of growth and maturation.
Developmental Disturbances of prenatal periods
Preimplantation Period:
Down Syndrome caused by extra chromosome
Flat, broad face with wide eyes, flat nose, slanted eyes.
Abnormal shaped teeth and periodontal disease.
Embryonic Period:
Rubella virus in measles from mother can cause heart defects and deafness in child.
High level of radiation can cause mental and physical developmental restrictions.
Fetal Alcohol Syndrome (FAS).
Fetal Period:
Tetracycline – permanent staining on child’s primary teeth.
Occurs when mother takes antibiotic tetracycline.
When does the heart begin beating?
It typically starts around the 5th week of pregnancy (or about 22 days after conception).
Structures formed by Embryonic Layers
Ectoderm:
- Skin , brain, spinal cord
- Enamel of teeth
- Lining of oral cavity
Mesoderm:
- Bones and muscles
- Dentin, pulp, and cementum of teeth
- circulatory system
Endoderm:
Lining of lungs and digestive system
Stomodeum
The stomodeum, or primitive mouth is depression in the ectoderm of the oral region of young embryo, which develops into the mouth and oral cavity. Develops on forth week.
