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Questions and Answers
What do the zygomatic bones and temporal bones form?
The sides of the upper lip.
Which of the following structures are a part of the brachial apparatus?
When does the palate begin formation?
In the 5th week.
The primary palate contains the maxillary canines and posterior teeth.
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What is the main function of the cervical loop in root development?
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Which type of mucosa includes the buccal and alveolar mucosa?
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What happens during the initiation stage of tooth development?
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Cementum can continue to be produced after tooth eruption.
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What type of epithelium is found in the lining mucosa?
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What are the primary cells found in the pulp of a tooth?
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What are the functions of the central cells of the dental papilla?
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What is the largest group of cells found in the dental pulp?
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The two types of cementum are ___ and ___ cementum.
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Which cell types are found in alveolar bone?
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What mineral composition makes up calcium hydroxyapatite?
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The periodontal ligament (PDL) is innervated and vascular.
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What are the main types of fiber groups found in the PDL?
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Match the following pulp zones with their descriptions:
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Which of the following are the four basic histological types of tissues?
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What tissue type covers and lines the external and internal body surfaces?
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Epithelial tissue is vascular.
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What is the classification of epithelial tissues based on?
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What are rete ridges?
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The _____ layer of the basement membrane is nearer to the epithelium.
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What is the most common cell type in all types of connective tissue?
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Which type of connective tissue serves as a skeletal tissue in the body?
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What type of cartilage is the most common?
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Match the following types of muscle tissue with their characteristics:
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What is the primary function of nerve tissue?
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Mitosis results in daughter cells that are genetically identical to the parent cell.
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The _____ period of prenatal development begins at the start of pregnancy.
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What happens during the preimplantation period?
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Which layer of the embryo develops into the central nervous system?
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What does the mandibular arch give rise to?
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The frontonasal process gives rise to the upper lip.
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Study Notes
Histology Overview
- Tissues classified into four basic types: Epithelial, Connective, Muscle, Nerve.
Epithelial Tissue
- Covers and lines external and internal body surfaces including vessels and cavities.
- Composed of closely packed polyhedral cells with minimal intercellular substance.
- Cells tightly joined by desmosomes; attach to non-cellular surfaces through hemidesmosomes.
- Avascular, obtaining nutrients by diffusion from adjacent connective tissue; exhibits rapid turnover rates.
Classification of Epithelial Tissues
- Simple epithelium: single layer of cells.
- Stratified epithelium: two or more layers; only the basal layer contacts the basement membrane.
- Stratified squamous epithelium is the most common type.
Rete Ridges
- Extensions of epithelium into connective tissue, known as rete ridges or rete pegs.
Basement Membrane
- Thin acellular layer separating epithelium from connective tissue; consists of two layers:
- Basal lamina (with lamina lucida and lamina densa) and reticular lamina.
- Basal lamina anchors to connective tissue.
Connective Tissue
- Composed of fewer, more dispersed cells with abundant intercellular substance and fibers.
- Generally vascularized, serving functions like support, transport, insulation, and defense.
- Fibroblast is the predominant cell type, with slower turnover compared to epithelial tissue.
Connective Tissue Layers
- Connective tissue proper has loose and dense layers.
- Papillary layer (loose connective tissue) and reticular layer (dense connective tissue) found under epithelium.
Cartilage
- Firm, non-calcified tissue serving as skeletal support; present in embryonic skeleton and joints.
- Avascular and relies on surrounding tissue for nutrition.
- Chondroblasts produce cartilage matrix; chondrocytes maintain it.
- Three types: Hyaline, Elastic, and Fibrocartilage.
Cartilage Growth
- Interstitial growth: from within the tissue.
- Appositional growth: from the outer layers.
Bone
- Rigid connective tissue that forms the skeleton, with periosteum as the outer covering.
- Compact bone: heavy, dense; Cancellous bone: lighter with spaces.
- Bone matrix formed initially as osteoid by osteoblasts; osteocytes maintain it, while osteoclasts resorb bone.
Blood
- Fluid connective tissue transporting nutrients; composed of plasma and cells.
- Key formed elements: red blood cells (RBCs), white blood cells (WBCs), platelets.
- RBCs transport oxygen and carbon dioxide; WBCs play a role in immune response; platelets assist in clotting.
Muscle Tissue
- Muscular system consists of three types: Smooth (involuntary), Cardiac (involuntary), Skeletal (voluntary).
- Skeletal muscle is striated, made up of myofibrils composed of myofilaments.
Nerve Tissue
- Nerves consist of bundles of neural processes; transmit electrical impulses for muscle contraction, gland stimulation, and sensation.
- Neurons are the functional unit, made up of a cell body, axon, and dendrites.
Developmental Processes
- Mitosis results in two genetically identical daughter cells; meiosis reduces chromosomes for reproductive cells.
Prenatal Development
- Begins at conception; consists of preimplantation, embryonic, and fetal periods.
- Preimplantation: zygote formation and initial cell division.
Embryonic Period
- From implantation to the 8th week; includes formation of bilaminar and trilaminar discs with ectoderm, mesoderm, and endoderm.
- Central nervous system development begins; neural crest contributes to face and neck structures.
Fetal Period
- From week 9 to birth; marked by maturation of the embryo into a fetus.
Facial and Palatal Fusion
- Facial fusion: elimination of grooves between swellings; palatal fusion involves merging of structures from different surfaces.
Brachial Apparatus
- Composed of branchial arches, grooves, and pharyngeal pouches, contributing to head and neck structures.
- First branchial groove forms the external auditory meatus; other grooves disappear by seventh week.
Palatal Development
- Begins in the 5th week; intermaxillary segment forms the primary palate which holds maxillary incisors.### Palate Development
- Primary palate separates nasal and oral cavities by the 5th week.
- Secondary palate forms from the maxillary processes during the 6th week, with palatal shelves fusing medially.
- Secondary palate comprises the posterior two-thirds of the hard palate, containing maxillary canines and posterior teeth, along with the soft palate and uvula.
- Complete fusion of the primary and secondary palates occurs from anterior to posterior.
Nasal Cavity and Septum Development
- Nasal cavity development occurs concurrently with palate formation between the 5th and 12th weeks.
- The vertical nasal septum fuses with the final palate by the 9th week, completing by the 12th week.
- This fusion fully separates the nasal and oral cavities.
Tongue Development
- The tongue develops from the 4th to 8th weeks through structures like the tuberculum impar, lateral lingual swellings, copula, and epiglottic swelling.
- By the end of the 8th week, the tongue has completed the fusion of its swellings and moves into the oral cavity.
Tooth Development
- Initiated in the 7th week with 20 primary teeth, continuing into late teens for 32 permanent teeth.
- Stages of tooth development include: bud stage, cap stage, bell stage, apposition stage, and maturation stage.
- Key structures involved: dental lamina, enamel organ, dental papilla, and dental sac.
Bell Stage
- Inner enamel epithelium (IEE) differentiates into ameloblasts forming enamel matrix.
- Dental papilla consists of outer cells for dentin formation (odontoblasts) and central cells that form primordium.
Apposition Stage
- IEE cells differentiate into preameloblasts, which induce odontoblast differentiation from outer dental papilla cells.
- Odontoblasts begin dentinogenesis from the basement membrane, while preameloblasts differentiate into ameloblasts and start amelogenesis.
Root Development
- Occurs post-crown completion; the cervical loop is crucial for root shape and dentin formation.
- The Hertwig's epithelial root sheath (HERS) is formed from the cervical loop, shaping the root and inducing dentin formation.
Cementum Formation
- After HERS disintegration, undifferentiated dental sac cells become cementoblasts, covering root dentin with cementoid.
Oral Mucosa
- Composed of stratified squamous epithelium and lamina propria, permitting flexibility, moisture, and connective tissue support.
- Categories include lining mucosa, masticatory mucosa, and specialized mucosa.
Lining Mucosa
- Characterized by soft texture, moisture, and stretchability; includes the buccal and labial areas.
- Histologically linked to non-keratinized stratified squamous epithelium.
Masticatory Mucosa
- Features rubbery texture and resiliency; includes attached gingiva and hard palate.
- Comprised of keratinized stratified squamous epithelium with pronounced connective tissue papillae.
Specialized Mucosa
- Present on the tongue within lingual papillae, with varied keratinization.
- Taste buds found in certain papillae types, contributing to taste sensation.
Types of Stratified Squamous Epithelium
- Non-keratinized is the most common and has three layers: basal, intermediate, and superficial.
- Ortho-keratinized is the least common and includes a keratin layer.
- Para-keratinized is found in masticatory mucosa with nucleated cells in the keratin layer.
Lamina Propria
- A support structure carrying nerves and blood vessels, consisting of a papillary layer (loose connective tissue) and a reticular layer (dense connective tissue).
Basement Membrane
- A thin, acellular structure between epithelium and connective tissue composed of a basal lamina and reticular lamina.
Specialized Mucosa of the Tongue
- Covered by lingual papillae, with different types including filiform, fungiform, foliate, and circumvallate, each contributing to taste sensation.
Tooth and Support Tissues
- Enamel: Avascular, non-renewable, produced by ameloblasts, with features like lines of Retzius.
- Dentin: Formed by odontoblasts through dentinogenesis.
- Pulp: Contains fibroblasts and odontoblasts, serving nutritive, formative, sensory, and protective functions.
- Cementum: Avascular, renewable tissue adhering the tooth, produced by cementoblasts.
- Alveolar Bone: Supports teeth, with terms such as cribriform plate and lamina dura.
- Periodontal Ligament (PDL): Connects teeth to the alveolar bone, consists of fiber bundles and cells like fibroblasts and osteoblasts.
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Description
This quiz focuses on Chapter 2 of Histology and Embryology, covering the classification and characteristics of basic tissues. It highlights the four histological types: epithelial, connective, muscle, and nerve tissues. Test your knowledge on the structural and functional roles of these essential tissue types.
