Module 2 | INTEGUMENTARY Leave the first rating

What is the largest organ of the human body?

skin

How much of the total body mass is skin?

7% of total body weight

What are the functions of the skin?

Protects
Screens
Synthesis of Vitamin D
Insulates/Cushions
Regulates Body Temperature
Excretes
Sense Organs (touch receptors)

What are the 4 distinct cell found in the epidermis?

-Keratinocytes
-Melanocytes
-Merkel Cells
-Langerhan's Cells

What do keratinocytes do?

produce keratin, most abundant (connected by desmosomes), protective properties (tough fibrous protein) produce antibiodicts

What do melanocytes produce?

found in (stratum basale) produce melanin. Melanin is transferred to nearby keratinocytes

What are Merkel cells?

associated w/disc like sensory endings. Receptors for touch.

What are Langerhan's cells?

found in (stratum spinosum) police outer body surface, using receptor mediated endocytosis takeup antigens. Killer T lymphocytes

What are the layers of the epidermis?

5 layers composed

Stratum Basale

Stratum Spinosum

Stratum Granulosum

Stratum Lucidum

Stratum Corneum

Stratum Basale (Basal Layer)

deepest epidermal layer attached to underlying dermis. Consists of single row of cell (mostly smooth cells). Layers rapidly divided via mitosis

Stratum Spinosum (Spiny Layer)

several cell layers thick, mitosis occurs here but less often than basale layer, cells contain thick bundle of intermediate filaments (tonofilaments) "tension filaments

Stratum Granulosum (Granular Layer)

1 to 5 layers of flattened keratinocytes

Keratohyaline Granules - keratin in higher strata

Lamellated Granules-water proofing glycolipids secrete into extracellular space (slows down water loss)

Stratum Lucidum (Clear Layer)

occurs only in thick skim
consists of a few rows of flat dead karatinocytes

Stratum Corneum (Horny Layer)

external part of epidermis, many layers of dead keratinocytes resemble flat sacs fill with keratin, nuclei & organelles disintegrate upon death, protect skin against abrasion & penetration

What are epidermal ridges?

found on palms & soles
dermal papillae lie atop larger mounds
fingerprints, palm prints, & foot prints

What causes stretch marks (striae) with obesity or pregnancy?

extreme stretching of the skin can tear the collagen in the dermis

Is the hypodermis officially part of the skin?

No. It is below the skin.

What do UV rays stimulate the deep dermis for?

stimulate the deep dermis to produce Vitamin D

What layer has the most adipose connective tissue?

the hypodermis

What layer contains melanin/pigment?

the basale layer

What cell polices the body surface using receptor mediated endocytosis?

Lagerhan's cells

Which cell is the most abundant in the epidermis?

keratinocytes

What is keratin?

tough fibrous protein that gives epidermis its protective properties

What happen when Langerhan's cells leave the skin?

they travel to near by lymph nodes where they present antigens to Killer T lymphocytes

What are the 2 plexuses of the dermis?

Cutaneous Plexus (deep): between hypodermis & dermis
-nourishes hypodermis & structure located within deeper portion of the dermis

Subpapillary Plexus (superficial):just below dermal papillae
supplies more superficial dermal structures (dermalpapillae & dermis)

What hold the dermis and epidermis together?

stratum basale

What is sebum

-oily substance that acts a a lubricant to keep skin soft and moist and keep the hair from becoming brittle

collects dirt, prevents water loss, kills bacteria

What is true sweat?

- 99% water
- 1% salts (NaCl) and metabolic wastes (urea, ammonia, uric acid)

What is melanin?

made from amino acid called tyrosine
varieties of yellow, reddish brown & black
made in melanocytes

What is hemoglobin?

crimson color of oxygenated hemoglobin

What is carotene?

yellow/orange pigment
accumulates in stratum corneum & fat in hypodermis
found in veggies like carrots/tomatoes

What is hair made of?

long filaments

How many layers does the hair have? What are they?

3 Centric Layers
Medulla
Cortex
Cuticle

What part of the hair is visible above the skin?

hair shaft

What does the nail rest on?

a bed of epidermis called the nail bed