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Skeletal system

Overview of Class Topics

This class covered various topics related to skin and skeletal systems, with a focus on cancer, burns, and the structure and function of bones and cartilage.

Cancer

Introduction to Cancer

Cancer is described as a complex biological phenomenon that can be both fascinating and concerning, particularly when it affects individuals personally. The implications of cancer encompass both genetic and environmental factors contributing to the overall risk profile for individuals.

Genetic and Environmental Factors

  • Genetic Factors: Represent the hereditary risk baseline for cancer.

  • Environmental Factors: External influences, such as chemical exposures, that can increase cancer risk.

  • The interaction between these two factors provides an individual's risk profile but lacks precise quantification.

  • There are few absolute certainties in cancer risk, as most cancers arise from a combination of genetic susceptibility and environmental exposure.

Key Carcinogens

  1. Radiation: Recognized as a clear carcinogen that can induce cancer without causing immediate lethality.

  2. Aflatoxin B: A potent carcinogen found in peanuts that leads to high rates of liver cancer in animal models.

  3. Tobacco Smoke: Approximately 30% of all cancers are attributed to tobacco use in its various forms, emphasizing its carcinogenic nature. Despite the known risks, not all smokers will develop cancer.

Tumor Suppressors and Cell Cycle

  • Tumor suppressor genes produce proteins that regulate cell division and prevent uncontrolled growth.

  • Mutations in these genes can increase susceptibility to specific cancers.

  • The cell cycle contains checkpoints that manage the transition from cell maintenance to division, influenced by tumor suppressor and promoter genes.

Mutation and Cancer Development

  • Not all mutations lead to cancer; many do not impact cell function.

  • A mutation can cause cell death, facilitate cancerous growth, or occur in non-crucial areas of DNA.

  • No one is entirely immune to cancer; lifelong exposure to carcinogens is an inevitability, highlighting the importance of awareness and preventive measures.

Burns and Skin

Types of Burns

  • First Degree Burn: Affecting only the outer layer of skin (epidermis).

  • Second Degree Burn: Involving the epidermis and part of the dermis.

  • Third Degree Burn: Extending through the epidermis and dermis, possibly affecting fat, muscle, or bone.

Rule of Nines

  • The body is divided into sections to assess burn severity, with each section representing approximately 9% of total body surface area. This evaluation helps determine treatment and urgency in clinical settings.

Consequences of Burns

  • Significant burns (especially second-degree) can lead to fluid loss, dehydration, and increased risk of infection due to breached skin barriers.

  • Renal failure is often a consequence of severe burns affecting water retention and loss.

Skeletal System

Cartilage and Bone

Types of Cartilage

  1. Hyaline Cartilage: Provides support and flexibility; found in joints, ribs, and parts of the respiratory system.

  2. Fibrocartilage: Contains more fibrous elements; found in intervertebral discs and pubic symphysis.

  3. Elastic Cartilage: Provides strength and elasticity; found in structures like the ear and epiglottis.

Bone Structure and Function

  • Bones provide support, protection, and movement, in addition to serving as a reservoir for minerals and a site for blood cell formation (hematopoiesis).

  • Bone growth occurs via both appositional (widening) and interstitial (lengthening) growth, with cartilage acting as a precursor to bone formation.

Composition of Bone

  • Periosteum: The outer covering of bone, essential for attachment and nourishment.

  • Endosteum: Lining the internal surfaces of bone; involved in bone remodeling and repair.

  • Bone Cells:

    • Osteogenic Cells: Stem cells that divide to form osteoblasts.

    • Osteoblasts: Build bone tissue and are actively mitotic.

    • Osteocytes: Mature bone cells, embedded in the matrix, which do not divide.

Bone Remodeling and Repair

  • Bone continuously undergoes remodeling; osteogenic cells differentiate into osteoblasts that secrete new bone matrix, which eventually becomes hard mineralized bone.

  • Osteoclasts are specialized cells that break down bone tissue, maintaining the balance with osteoblast activity.

Overall, this class provided a comprehensive overview of skin structure, cancer risks, and the intricacies of skeletal systems, setting the stage for deeper exploration in future classes.