Notes, summaries, assignments, exams, and exercises for Biology for University

Structure of the Centriole

In general, all cells have two centrioles located near the nucleus or a notch on the concave side of the Golgi apparatus. The centriole is a cylinder measuring 0.15-0.25 µm wide and 0.3-0.7 µm in length, comprising:

• A peripheral part: 0.04-0.05 µm in thickness, which contains nine groups of three or triplets of microtubules (MT).
• A central part: Usually clear, though it may sometimes contain one or two granules.
• A proximal end: The end closest to the center of the cell.
• A distal end: Directed towards the periphery, which encloses a complex system known as a cartwheel, present only during immature centriole elongation.

Microtubule Triplets and Arrangement

The centriolar wall consists of nine triplets. Each triplet is formed...

Microbiology: The Science of Microorganisms

Microbiology, derived from the Greek words mikros ("small"), bios ("life"), and logos ("study"), is the scientific discipline dedicated to the study of microorganisms. These are living things too small to be seen with the naked eye. Microorganisms, often called germs, were discovered over 300 years ago. Their only common characteristic is their small size.

Microscopy depends on factors such as contrast, resolution, and magnification.

Taxonomy involves the study of nomenclature, classification, and identification of microorganisms.

Factors Influencing Microbial Growth

The number and types of microorganisms in an environment depend on factors like humidity, heat, nutrient availability, aeration, and pH.

• Soil

Nervous System: Definition and Functions

The nervous system is defined by its general duties, including the nervous system of the life of relation, its definition, and functions. This includes the cortex, functions of the cortex, voluntary motility, and sensitivity. It also encompasses sensory systems (olfaction, taste, sight, hearing, and touch), consciousness, dreams, and comas. Additionally, it covers the vegetative or autonomic nervous system, its definition, general duties, anatomy, afferents, efferent pathways, and physiology.

The nervous system (NS) governs relations with the outside world and adjusts and coordinates the activities of organs. This separates two functions that are interrelated but very different from each other. Thus, relations...

Intermaxillary Registration in Dentures

Vertical Dimension

A measurement of the lower third of the face using two arbitrary points: one above the superior lip and one below the inferior lip.

Vertical Dimension at Rest (Postural)

The measurement of the lower third of the face when the levator and depressor muscles of the jaw are in minimum tonic contraction to maintain the jaw position against gravity. In this state, the dental arches are not touching, the lips have a soft contact, and the teeth are separated by an inter-occlusal space (freeway space) typically measuring 2 to 4 mm.

Vertical Dimension in Occlusion

The measurement of the lower third of the face when the teeth are in contact. The lips are in contact, and there is no inter-occlusal space....

Citric Acid Cycle

The citric acid cycle is a series of eight reactions in which an acetyl group is decarboxylated and oxidized, generating:

• 3 molecules of NADH
• 1 molecule of FADH2
• 2 molecules of CO2
• 1 molecule of ATP (or GTP)

For each molecule of glucose entering glycolysis, two molecules of pyruvate are produced. Pyruvate is then converted to two molecules of acetyl CoA, which can enter this cycle.

Oxygen is used indirectly in cellular respiration. Glycolysis breaks down a glucose molecule, generating two molecules of pyruvate. Pyruvate moves into the mitochondrial matrix. Inside the matrix, pyruvate is converted to acetyl CoA, which then enters the citric acid cycle.

Key steps in the cycle include:

• Acetyl CoA reacts with a molecule of oxaloacetate

Class 1 Malocclusion: Issues and Variations

Crossbite Complications

Crossbite (failure of dental arches to occlude correctly in the lateral dimension) can manifest in several ways within Class 1 malocclusion (normocclusion, often with a good relationship between the osseous bases):

• Unilateral Crossbite: Affects one side, from the canine to the last molar.
• Bilateral Crossbite: Affects both sides, from canine to molar. Often associated with maxillary micrognathia (narrow upper jaw) relative to the mandible. May be linked to habits like mouth breathing and finger sucking.
• Dental Crossbite: Normocclusion with a good skeletal base relationship, but involves incorrect inclination of a specific molar or canine due to lack of space, resulting in palatal

Teratogens Affecting Dentofacial Development

Teratogens are agents that can cause developmental abnormalities in the fetus. Specific effects on the developing dentofacial structures include:

• Ethyl Alcohol: Associated with central midfacial deficiency.
• Aminopterin: Linked to anencephaly.
• Aspirin, Dilantin, Valium, and Snuff Smoke: Associated with Cleft Lip and Palate (LPH).
• Toxoplasma: Can cause hydrocephalus, microcephaly, and microphthalmia.
• Hypervitaminosis D: May lead to premature closure of sutures.
• X-Rays: Associated with microcephaly.
• Rubella Virus: Can cause deafness, microphthalmia, and cataracts.

Trauma and Growth Disorders

Trauma, particularly during critical developmental periods, can lead to significant growth disorders in the craniofacial...

Thyroid Hormone Synthesis Pathway

1. Thyroglobulin (TG) Synthesis and Transport

   TG synthesis occurs in the Rough Endoplasmic Reticulum (RER) and Golgi apparatus. The synthesized TG is then transported to the follicular lumen.

2. Iodide Uptake (Iodide Pump)

   Iodide (I-) enters the follicular epithelial cells via the sodium-iodide symporter (NIS) pump. Inhibitors such as perchlorate and thiocyanate block the uptake of iodide into the follicular cells, thereby interfering with thyroid hormone synthesis.

3. Oxidation of Iodide (I- to I2)

   Iodide crosses the apical membrane where it is oxidized to form molecular iodine (I2). The enzyme Thyroid Peroxidase (TPO) catalyzes this oxidation in two steps. Propylthiouracil (PTU) inhibits TPO, blocking hormone synthesis.

The Conducting Portion of the Respiratory System

The conducting portion consists of the nasal passages, nasal pharynx, larynx, trachea, and bronchioles.

The Larynx: Phonation and Protection

The larynx anatomically links the pharynx to the trachea. Its primary functions include phonation, swallowing, and breathing. It prevents different substances from entering the interior and features a cartilaginous structure with stratified squamous epithelium and flat folds. Internally, it is lined with pseudostratified ciliated columnar epithelium, which extends from the larynx through the trachea and into the bronchi.

The Trachea: Structure and Cell Types

The trachea extends from the larynx to the carina. It is composed of 16-20 semilunar cartilaginous rings...

Clinical and Dental Terminology

• Biopsy: Removal and examination of a tissue sample from a living body for diagnostic purposes.
• Bruising: A blue coloring of the skin caused by injury.
• Carcinoma: An invasive malignant tumor that tends to metastasize to other areas of the body.
• CVS: Abbreviation for the cardiovascular system.
• Debris: Unwanted waste material.
• Degenerative disease: A disorder in which the patient's condition slowly worsens and deteriorates.
• Derangement: An abnormality in the usual arrangement.
• Erupted: Visible (specifically regarding teeth).
• Erythematous: Reddening of the skin caused by the dilation and congestion of capillaries.
• Excision biopsy: The complete removal of a lesion for microscopic examination.
• External auditive meatus: The canal