Lecture 7: Integumentary System

Stratum Structures of the Epidermis

The epidermis is composed of several layers, each with distinct functions and cell types. Understanding the structure is essential for grasping skin physiology and pathology.

• Stratum basale: Deepest layer, site of cell division.

• Stratum spinosum: Provides strength and flexibility.

• Stratum granulosum: Cells begin to die and keratinize.

• Stratum lucidum: Present only in thick skin (palms, soles).

• Stratum corneum: Outermost layer, composed of dead, keratinized cells.

Keratinization is the process by which keratinocytes mature and fill with keratin, eventually dying and forming the protective outer layer.

Melanocyte Functions

• Melanocytes produce melanin, the pigment responsible for skin color.

• Melanin protects underlying tissues from UV radiation.

Sebaceous Glands

• Sebaceous glands secrete sebum, an oily substance that lubricates skin and hair.

• Found throughout the skin except on palms and soles.

Inflammatory Response

• The skin initiates an inflammatory response to injury or infection, involving immune cells and chemical mediators.

Sample Question Example

• Epidermal cells with the highest metabolic demands are found furthest from the basal lamina because diffusion distance is at its greatest.

• Sebaceous glands are found over almost the entire skin surface except: Palms of hands, soles of feet, forehead.

Lecture 8: Bone Tissue and Homeostasis

Bone Cell Types

Bones contain several specialized cell types, each with unique functions in bone formation and maintenance.

• Osteocytes: Mature bone cells that maintain bone tissue.

• Osteoblasts: Cells responsible for bone formation.

• Osteoprogenitor cells: Stem cells that differentiate into osteoblasts.

• Osteoclasts: Cells that break down bone tissue.

Spongy Bone Characteristics

• Spongy bone is composed of trabeculae and contains red bone marrow.

• Provides structural support and flexibility.

Bone Remodeling

• Bone remodeling is a continuous process involving resorption by osteoclasts and formation by osteoblasts.

Hormonal Regulation

• Calcitonin: Lowers blood calcium levels.

• Parathyroid hormone (PTH): Raises blood calcium levels.

Homeostasis in Bone

• Bones help maintain mineral homeostasis, especially calcium and phosphate.

• Openings in bone (foramina) allow nerves and blood vessels to pass through, supporting bone health.

Sample Question Example

• Foramina are used for the delivery of nutrients and removal of waste.

• Homeostasis in bone is maintained by: Hormonal regulation, mineral exchange, and cellular activity.

Lecture 9: Joints and Movement

Joint Classifications

Joints are classified based on their structure and the degree of movement they allow.

• Synarthrosis: Immovable joints (e.g., sutures in the skull).

• Amphiarthrosis: Slightly movable joints (e.g., intervertebral discs).

• Diarthrosis: Freely movable joints (e.g., synovial joints).

Types of Movements

• Flexion: Decreases the angle between bones.

• Extension: Increases the angle between bones.

• Abduction: Movement away from the midline.

• Adduction: Movement toward the midline.

Sample Question Example

• Extension of synovial joints: Increases the angle between elements.

Lecture 10: Muscle Tissue and Contraction

Muscle Fiber Structure

Muscle fibers contain specialized structures for contraction and force generation.

• Epimysium, Perimysium, Endomysium: Connective tissue layers surrounding muscle.

• Sarcomere: The functional unit of muscle contraction, composed of actin and myosin filaments.

Sliding Filament Theory

• Describes how actin and myosin filaments slide past each other to produce muscle contraction.

• ATP is required for myosin head movement and detachment.

Components of a Sarcomere

• Z line: Defines the boundaries of a sarcomere.

• M line: Center of the sarcomere.

• H band: Region containing only myosin filaments.

Role of Ions and Neurotransmitters

• Calcium: Triggers contraction by binding to troponin.

• Sodium: Involved in action potential propagation.

• Acetylcholine: Neurotransmitter that initiates muscle contraction at the neuromuscular junction.

Sample Question Example

• Why do muscle cramps and rigor mortis occur? Due to lack of ATP, preventing detachment of myosin heads from actin.

Lecture 11: Muscle Physiology and Metabolism

All-or-None Principle

The all-or-none principle states that a muscle fiber contracts completely or not at all in response to a stimulus above threshold.

ATP Production in Muscle

• Muscle cells produce ATP via aerobic metabolism (using oxygen) and anaerobic glycolysis (without oxygen).

Drugs Affecting the Neuromuscular Junction (NMJ)

• Certain drugs and toxins (e.g., Clostridium botulinum) can interfere with acetylcholine release, affecting muscle contraction.

Table: Bone Cell Types and Functions

Key Equations

• ATP Production (Aerobic):

• ATP Production (Anaerobic Glycolysis):

Additional info: Academic context and definitions have been expanded for clarity and completeness.