Bio cards 10/9/2026

Integumentary

What percentage of total body weight does the integumentary system account for, and what is its surface area?

16% of total body weight and 1.5–2 m² in area.

What are the two major components of the integumentary system?

1. Cutaneous membrane (skin)

2. Accessory structures (hair, nails, exocrine glands)

Cutaneous membrane

Skin

Name the two layers of the cutaneous membrane and the layer immediately beneath it.

1. Epidermis (superficial epithelium)

2. Dermis (underlying connective tissue)
   Subcutaneous: Hypodermis (not part of the integument)

What are the two layers of the dermis, and what tissue types compose them?

1. Papillary layer: Areolar connective tissue

2. Reticular layer: Dense irregular connective tissue

What type of tissue makes up the epidermis?

Stratified squamous epithelium.

Papillary layer:

Areolar connective tissue

Reticular layer:

Dense irregular connective tissue

What type of tissue dominates the hypodermis, and what is its main function?

Adipose (fat) tissue. It stabilizes the skin relative to deeper structures while allowing independent movement.

What is the most abundant cell type in the epidermis?

Keratinocytes (continuously produced in deep layers and shed at the surface).

What structures lock the epidermis and dermis together?

Epidermal ridges of the epidermis interlock with dermal papillae of the dermis

What mnemonic helps remember the layers of the epidermis from superficial to deep, and what are the layers?

"Come, Let's Get Sun Burned"Corneum

1. Corneum

2. Lucidum (absent in thin skin)

3. Granulosum

4. Spinosum

5. Basale

Which epidermal layer contains immune cells, and what are those cells called?

Stratum spinosum; it houses dendritic cells to defend against pathogens and superficial cancers.

Which epidermal layer undergoes active cell division (mitosis)?

Stratum basale (contains basal stem cells).

From what amino acid is melanin synthesized, and what vesicles package it?

Synthesized from tyrosine and packaged into melanosomes.

Is skin pigmentation determined by the number of melanocytes?

No. It is determined by the synthetic activity of the cells, not the total number of melanocytes.

What is cyanosis, and what causes it?

A blue skin coloration visible in thin skin areas (lips, nails). It is caused by dark red, low-oxygen blood.

Contrast Basal Cell Carcinoma and Malignant Melanoma in terms of danger.

• Basal Cell Carcinoma: Most common, originates in stratum basale, virtually no metastasis, highly survivable.

• Malignant Melanoma: Cancer of melanocytes, highly metastatic (via lymphatics), 5-year survival drops from 99% to 14% if not caught early.

Basal Cell Carcinoma:

Most common, originates in stratum basale, virtually no metastasis, highly survivable.

Malignant Melanoma:

• Cancer of melanocytes, highly metastatic (via lymphatics), 5-year survival drops from 99% to 14% if not caught early.

What are lines of cleavage, and why are they clinically significant?

Structural patterns of collagen and elastin fibers. Incisions parallel to them heal better with less scarring; perpendicular cuts pull open and scar severely.

Why are severe burns an immediate threat to life?

They break the skin barrier, causing catastrophic fluid/electrolyte loss (up to 5x normal rate), disrupting thermoregulation, and risking fatal widespread infection (sepsis).

Describe the damage and symptoms of a Second-Degree Burn.

Damages the entire epidermis and parts of the dermis. Causes blistering, pain, and swelling. Heals in 1–2 weeks; accessory structures remain intact.

Why are Third-Degree Burns often less painful than second-degree burns?

Because sensory nerves are completely destroyed by the full-thickness damage.

How do clinicians quickly evaluate burn depth and burned surface area?

• Depth: Pin prick test (no sensation = third-degree).

• Surface Area: The Rule of Nines (modified for children).

Differentiate between an Autograft, Allograft, and Xenograft.

• Autograft: Patient's own undamaged skin (best choice; no immune rejection).

• Allograft: Frozen skin from a human cadaver.

• Xenograft: Skin from an animal.

Autograft

• Patient's own undamaged skin (best choice; no immune rejection).

Allograft

Frozen skin from a human cadaver.

Xenograft

• Skin from an animal.

Differentiate between Terminal Hairs and Vellus Hairs.

• Terminal: Large, coarse, darkly pigmented (scalp, armpits).

• Vellus: Smaller, shorter, delicate hairs covering the general body surface.

What nerve network and smooth muscle are associated with hair follicles?

• Root hair plexus: Sensory nerves tracking follicle touch.

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

Terminal hairs

• Large, coarse, darkly pigmented (scalp, armpits).

Vellus hair

Smaller, shorter, delicate hairs covering the general body surface.

Root hair plexus

Sensory nerves tracking follicle touch.

Arrector pili muscle:

• Smooth muscle that makes hair stand up (goosebumps).