4-Skin and urinary system physical therapy 2025 dr. manal

Department Details

  • Department of Histology

  • Faculty of Physical Therapy

  • Sphinx University

  • Instructor: Dr. Manal M. Sayed

Overview of Skin

  • Skin: Largest organ of the body

    • Accounts for 15%-20% of total body weight

  • Composition:I. Epidermis:

    • Superficial layer of stratified squamous keratinized epitheliumII. Dermis:

    • Deep layer of connective tissue

  • Subcutaneous Tissue (Hypodermis):

    • Loose connective tissue layer containing adipocytes (fat cells)

Types of Skin

  • Thick Skin: Found on palms and soles

  • Thin Skin: Found elsewhere on the body

    • Thickness refers to the epidermal layer only

Epidermis

Cell Types of the Epidermis

  • Composed of four types of cells:

    1. Keratinocytes

    2. Melanocytes

    3. Langerhans cells

    4. Merkel cells

Keratinocytes

  • Main Cell Type in the epidermis

  • Responsible for keratin formation

  • Organized in 5 Layers:

    1. Basal Layer

    2. Spinous Layer

    3. Granular Layer

    4. Clear Layer

    5. Cornified Layer

Layers of the Epidermis

  1. Basal Layer:

    • Rests on the basement membrane

    • Single layer of basophilic columnar cells; common mitosis

  2. Spinous Layer:

    • Formed of several layers of polyhedral cells

  3. Granular Layer:

    • Composed of several layers of flattened cells containing basophilic granules

  4. Clear Layer:

    • Present in thick skin; several layers of flattened cells with degenerated nuclei

  5. Cornified Layer:

    • Composed of dead cells filled with keratin

Non-keratinocytes

  1. Melanocytes

    • Produce melanin pigment

  2. Langerhans Cells

    • Antigen-presenting cells

  3. Merkel Cells

    • Sensory receptors

Dermis

  • Connective Tissue beneath the epidermis

  • Layers of Dermis:

    1. Papillary Layer: Thin layer of loose connective tissue forming dermal papillae

    2. Reticular Layer: Thick layer of dense connective tissue

Skin Appendages

  • Epidermal Derivatives:

    1. Sweat Glands:

      • Eccrine and apocrine

    2. Sebaceous Glands

    3. Hairs

    4. Nails

Sweat Glands

Type

Eccrine Sweat Gland

Apocrine Sweat Gland

Site

Present all over the body

Present in axilla

Secretory Part

Small lumen

Larger lumen

Duct

Opens into skin surface

Opens into hair follicle

Nature of Secretion

Watery sweat

Slightly viscous sweat

Onset of Action

Since birth

After puberty

Sebaceous Glands

  • Site: Found in thin skin near hair follicles

  • Duct: Opens into hair follicle

  • Nature of Secretion: Oily secretion (sebum)

  • Mode of Secretion: Holocrine

Structure of Hair

  • Keratinized Filaments: Derived from invagination of basal layer of epidermis into the dermis

  • Parts:a) Root: Deep in the skinb) Shaft: Projects above the surface

Layer Comparison: Thick vs. Thin Skin

Features

Thick Skin

Thin Skin

Site

Palms & soles

Found elsewhere

Epidermis

Thick

Thin

Dermis

Thin

Thick

Eccrine Sweat Glands

Numerous

Less

Apocrine Sweat Glands

Absent

Present

Sebaceous Glands

Absent

Present

Hairs

Absent

Present

Functions of the Skin

  • Covers internal structures

  • Protects from trauma and bacteria

  • Prevents loss of water and electrolytes

  • Senses temperature, pain, touch, pressure

  • Regulates body temperature through sweat production and evaporation

  • Synthesizes Vitamin D

  • Promotes wound repair

  • Provides insulation

Functions of the Kidney

  • Main Function: Urine formation and maintaining homeostasis

  1. Excretion of waste products (urea, uric acid)

  2. Retention of vital substances (glucose, amino acids, bicarbonate, proteins, sodium, chloride)

  3. Hormone Secretion:

    • Erythropoietin (stimulates blood cell formation)

    • Renin (regulates blood pressure)

  4. Activation of Vitamin D

Topics for Review

  1. Structures of Renal Corpuscles:

    • Bowman's capsule

    • Glomerulus

  2. Characteristics of Epithelium in Renal Structures

  3. Functions of Podocytes

  4. Filtration Barrier Components

  5. Differences between Proximal and Distal Convoluted Tubules

  6. Functions of the Kidneys and Skin