Integumentary System and Appendicular Skeleton: Key Structures and Features

Integumentary System

Overview of the Integumentary System

The integumentary system is composed of the skin and its associated structures, including glands, hair, and nails. It serves as the body's first line of defense, provides sensory information, and helps regulate temperature.

• Epidermis: The outermost layer of the skin, composed of stratified squamous epithelium.

• Dermis: The deeper layer of the skin, containing connective tissue, blood vessels, nerves, and appendages.

• Hypodermis (Subcutaneous layer): Not always considered part of the skin, but lies beneath the dermis and contains adipose tissue.

Key Structures to Identify on Models and Slides

• Epidermis

• Dermis

• Papillary layer/Dermal papillae: The upper layer of the dermis, characterized by projections that interlock with the epidermis.

• Reticular layer: The deeper, thicker part of the dermis.

• Hair shaft: The visible part of the hair above the skin surface.

• Hair root: The portion of the hair below the skin surface.

• Hair follicle: The structure in the dermis from which hair grows.

• Tactile (Meissner's) corpuscle: Sensory receptor for light touch.

• Lamellar (Pacinian) corpuscle: Sensory receptor for deep pressure and vibration.

• Eccrine sweat gland: Produces watery sweat for thermoregulation.

• Apocrine sweat gland: Found in specific areas (e.g., axilla), produces thicker secretion.

• Sebaceous gland: Secretes sebum (oil) into hair follicles.

• Arrector pili muscle: Smooth muscle that causes hair to stand up (goosebumps).

Layers of the Epidermis (from superficial to deep)

The epidermis consists of several distinct layers, especially prominent in thick skin (palms and soles):

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

• Stratum lucidum (L): Thin, clear layer found only in thick skin.

• Stratum granulosum (G): Layer where keratinization begins.

• Stratum spinosum (S): Several layers of keratinocytes, provides strength and flexibility.

• Stratum basale (B): Deepest layer, site of cell division and melanocyte location.

Mnemonic: "Come, Let's Get Sun Burned" (Corneum, Lucidum, Granulosum, Spinosum, Basale)

Table: Layers of the Epidermis

Layer	Abbreviation	Key Features
Stratum corneum	C	Dead, keratinized cells; barrier function
Stratum lucidum	L	Clear layer; only in thick skin
Stratum granulosum	G	Keratinization begins; granules visible
Stratum spinosum	S	Several layers; desmosomes give spiny appearance
Stratum basale	B	Mitotically active; melanocytes present

Example: Application to Scalp Slides

• On slides of the scalp, identify the above layers and structures such as hair follicles, sebaceous glands, and sweat glands.

• Recognize differences between thick and thin skin based on the presence or absence of certain layers (e.g., stratum lucidum).

Appendicular Skeleton

Overview of the Appendicular Skeleton

The appendicular skeleton includes the bones of the limbs and the girdles that attach them to the axial skeleton. It is essential for movement and manipulation of the environment.

Key Bones and Features to Identify

Bone	Identify L/R	Key Features
Clavicle	No	No required markings to identify
Scapula	Yes	Acromion, coracoid process, glenoid cavity, borders (superior, medial, lateral), angles (superior, inferior), spine, supraspinous/infraspinous/subscapular fossae
Humerus	Yes	Head, greater/lesser tubercle, intertubercular sulcus, deltoid tuberosity, epicondyles, capitulum, trochlea
Radius	Yes	Head, radial tuberosity, styloid process, ulnar notch
Ulna	Yes	Olecranon, trochlear notch, coronoid process, radial notch, styloid process
Bones of the hand	No	Phalanges (proximal, middle, distal), metacarpals I-V, carpals (individual bones not required)
Ilium	See below	Iliac crest, anterior/posterior superior/inferior iliac spines, greater sciatic notch, iliac fossa, acetabulum
Ischium	See below	Ischial tuberosity, ischial spine, obturator foramen, ischial ramus
Pubis	See below	Superior/inferior pubic ramus, pubic crest, pubic symphysis
Femur	Yes	Head, neck, greater/lesser trochanter, intertrochanteric line/crest, gluteal tuberosity, linea aspera, condyles, epicondyles, patellar surface
Tibia	Yes	Intercondylar eminence, condyles, tuberosity, medial malleolus, fibular notch
Fibula	Yes	Head, lateral malleolus
Bones of the foot	No	Phalanges (proximal, middle, distal), metatarsals I-V, tarsals (identify talus and calcaneus specifically)

Definitions and Key Terms

• Phalanges: Bones of the fingers and toes, classified as proximal, middle, and distal.

• Metacarpals/Metatarsals: Bones of the hand/foot between the phalanges and the carpal/tarsal bones.

• Tarsals/Carpals: Bones forming the wrist (carpals) and ankle (tarsals).

• Acetabulum: The socket in the pelvis that receives the head of the femur.

• Glenoid cavity: The socket in the scapula for the head of the humerus.

Example: Application in Lab

• Be able to identify bones and their features on models or real specimens.

• Distinguish left from right for bones where required (e.g., humerus, femur, scapula).

• Use anatomical landmarks (e.g., tuberosities, condyles, notches) to aid identification.

Additional info:

• Mnemonic devices are helpful for memorizing the order of epidermal layers.

• Understanding the function of each bone feature (e.g., muscle attachment, articulation) aids in identification and application.