V

Integumentary system

Introduction

  • Discussion about hip replacements and their failure rates.

    • Exploration of the reasons behind failure serving as a key motivator for further investigation.

Hip Replacement Overview

  • Definition: A surgical procedure where the hip joint is replaced with prosthetic components.

  • Conditions Leading to Replacement:

    • Inflammation in the hip joint (often due to arthritis).

    • Osteoporosis can contribute to joint deterioration.

Surgical Procedure Details

  • Total Hip Replacement: Removal of the head of the femur (the ball part) and the acetabulum (the socket part of the pelvis).

    • Components of Procedure:

    • Removal of the ball of the femur.

    • Placement of a metal ball in place of the original femoral head.

    • Insertion of a metal socket or cup into the acetabulum.

  • Partial Hip Replacement: Only the head of the femur may be replaced, leaving part of the pelvis intact.

Materials Used in the Replacement

  • Materials:

    • Traditionally, metal-on-metal connections have been used, although not ideal due to wear and tear.

    • Current practice involves lining metal components with plastic or other lining materials to prevent direct metal-metal contact.

Reasons for Hip Replacement Failure

  • Mechanism of Failure:

    • Complications arise from metal and plastic shavings that accumulate due to friction during joint movement.

    • These shavings induce inflammation in the surrounding tissues.

  • Immune Response:

    • The body reacts to the presence of foreign materials by triggering an immune response.

    • This response leads to inflammation which causes additional weakening of the surrounding bone structures.

    • As the bone weakens, the prosthetic parts can become loose, leading to complications.

General Observations on Joint Replacements

  • Differentiation from Other Replacements:

    • Other joint replacements (e.g., knee) fail due to varied reasons unlike hip replacements.

    • The primary failure mechanism in knee and other joint replacements can vary and often revolves around design or surgical technique issues.

Transition to Skin and Bone Discussion

  • Discussion was shifted back to skin and bone, emphasizing the importance of understanding skin layers.

Skin Structure

  • Discussion of skin layers commenced, focusing on:

    • Dermis: Located under the epidermis, primarily made of connective tissue.

  • Epidermal Layers:

    • Five main layers were previously discussed.

Friction Ridges and Fingerprints

  • Definition and Explanation:

    • Friction ridges are patterns found on the skin's surface, most notably on fingertips – these patterns contribute to our unique fingerprints.

    • These ridges arise from the arrangement of capillary loops in the papillary layer of the dermis.

  • Importance of Friction Ridges:

    • Enhances tactile sensitivity: The ridges increase the ability to feel different textures and vibrations.

    • Theories on Friction Ridge Function:

    • Improves grip on surfaces.

    • Aids in moisture management when gripping wet objects.

Clarifying Misconceptions

  • Clarified the differences between microscopic and macroscopic features in skin structure.

  • Microscopic Wavy Lines: Demarcation between the epidermis and dermis, too small to be seen without a microscope.

  • Macroscopic Friction Ridges: These can be seen with the naked eye, arising from the arrangement of collagen fibers in the dermis.

Dermal Layers Breakdown

  • Papillary Layer: Comprised of areolar loose connective tissue facilitating epidermal-nutrient transfer.

  • Reticular Layer: Denser regular connective tissue that provides strength and elasticity to the skin.

    • Cleavage Lines:

    • Invisible lines formed by collagen fiber orientation in the reticular layer; significant for surgical incisions and scar formation.

  • Flexure Lines: Visible lines on areas prone to movement, aiding in skin attachment during flexing motions.

Hypodermis

  • Definition: Also known as the subcutaneous layer, consists primarily of adipose tissue and areolar connective tissue.

  • Function: Acts as insulation and cushioning for bones and muscles.

Melanin and Skin Pigmentation

  • Melanin: The only pigment produced within the skin, created in melanocytes and distributed to keratinocytes.

    • Increased UV exposure leads to higher melanin production.

    • Freckles and moles are potential signs of localized melanin increase.

  • Purpose of Melanin: Primarily to protect against UV-induced DNA damage which can lead to mutations or skin cancer.

Bruises vs. Blisters

  • Bruises:

    • Result from capillary rupture and blood leakage under skin, leading to discoloration.

  • Blisters:

    • Formed from friction or burns separating the epidermis from the dermis, leading to fluid accumulation.

Calluses vs. Blisters

  • Calluses form through repeated friction where the epidermis thickens, while blisters form from acute trauma where fluid accumulates.

Hair and Its Function

  • Hair’s Role: Serves both tactile and protective purposes against UV radiation and physical impacts.

    • Although it contains keratin (hard keratin), it's structurally different from that found in the skin (soft keratin).

  • Hair Anatomy:

    • Composed of a shaft (visible part) and root (below the skin).

  • Matrix: The area within the hair follicle where new cells are produced, akin to the stratum basale in skin.

Nails Overview

  • Nails: Comprised of mostly keratinized cells, also beginning their life in a matrix similar to that in hair follicles.

  • Functions: Offer protection to the fingertips, providing scraping and gripping abilities.

Glands Associated with the Skin

  • Types of Sweat Glands:

    • Eccrine (common and produce sweat for thermoregulation), Apocrine (larger glands associated with body odor), and Sebaceous (producing oil for hair and skin).

Skin Functionality Summary

  1. Protection: Acts as the first barrier against environmental factors.

  2. Homeostasis: Regulates body temperature through sweat production.

  3. Sensation: Houses sensory receptors for touch, pain, and temperature variations.

  4. Metabolic Functions: Contributes to vitamin D synthesis and waste excretion.

Skin Cancer Types

  • Basal Cell Carcinoma: Most common and typically benign, originating from the stratum basale.

  • Squamous Cell Carcinoma: Arises from the stratum spinosum, can metastasize but is often more treatable.

  • Melanoma: The most dangerous type of skin cancer, highly metastatic and resistant to treatment.

Conclusion

  • Final remarks on the importance of skin and hair physiology in understanding broader health and medical topics, accompanied by reviews and connections to the upcoming exams.

  • Emphasis on proactive learning and retention for assessments.