Lawyers of skin

The "lawyers of skin" are dermatologists - physicians who specialize in diagnosing and treating conditions of the skin, hair, and nails. The nickname plays on the idea that dermatologists "defend" and care for the body's largest organ.

However, if you're asking about something more specific, let me know! For example:

Langerhans cells - the immune "sentinels" of the skin, acting as its defense lawyers against pathogens
The layers of skin (epidermis, dermis, hypodermis) - if this is a wordplay/riddle
A specific medical or pop culture reference

What did you have in mind?

Explain the layers of skin

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Here is a thorough breakdown of the layers of skin, drawn from Junqueira's Basic Histology and Histology: A Text and Atlas (Pawlina).

The Three Major Layers of Skin

The skin (integument) is the largest single organ of the body, accounting for 15-20% of total body weight and presenting about 1.5-2 m² of surface area. It is divided into three primary layers:

Diagrammatic overview of skin layers, appendages, and vasculature

1. Epidermis (Outermost Layer)

The epidermis is a keratinized stratified squamous epithelium derived from ectoderm. It lacks blood vessels - nutrients reach it by diffusion from the dermis. It contains mainly keratinocytes, plus three non-keratinocyte cell types:

Melanocytes - produce melanin pigment (UV protection)
Langerhans cells - antigen-presenting immune cells
Merkel cells - tactile/sensory epithelial cells

The epidermis is divided into 4 layers (5 in thick skin):

Histological section and diagram of epidermal layers in thick skin

From deep to superficial:

Layer	Key Features
Stratum Basale (basal layer)	Single layer of columnar/cuboidal cells on the basement membrane. High mitotic activity - this is where new keratinocytes are born. Cells attach via hemidesmosomes to the basal lamina.
Stratum Spinosum (spinous/prickle cell layer)	Several layers of polyhedral cells linked by prominent desmosomes. Keratin filaments bundle into tonofibrils. The "spiny" appearance comes from cell shrinkage around desmosomal connections. Source of squamous cell carcinoma.
Stratum Granulosum (granular layer)	3-5 layers of flattened cells packed with keratohyalin granules (filaggrin + keratins) and lamellar granules. Lamellar granules secrete lipids into the extracellular space, forming the water barrier.
Stratum Lucidum (thick skin only)	Thin, clear, refractile layer of dead keratinocytes. Nuclei and organelles are gone. Found only in palms and soles.
Stratum Corneum (cornified layer)	The outermost layer. Dead, flat "squames" composed almost entirely of keratin. Cells are shed (desquamated) from the surface in a pH-dependent process regulated by kallikrein proteases. The entire epidermis renews every 15-30 days.

Thick vs. Thin Skin:

Thick skin (palms, soles): all 5 layers present, epidermis 400-600 µm thick, hairless
Thin skin (everywhere else): 4 layers (no stratum lucidum), epidermis 75-150 µm thick, contains hair follicles

2. Dermis (Middle Layer)

The dermis is dense irregular connective tissue derived from mesoderm. It supports and nourishes the epidermis. It has two sub-layers:

Sub-layer	Features
Papillary layer	Superficial, thin. Contains dermal papillae that interdigitate with epidermal ridges (forming fingerprints). More cellular, thinner collagen fibers. Rich capillary network for epidermal nutrition.
Reticular layer	Deep, thick. Coarse bundles of collagen and elastic fibers providing strength and elasticity. Contains hair follicles, sweat glands, sebaceous glands, and sensory receptors.

Sensory receptors in the dermis include:

Meissner's corpuscles - fine touch (in papillary layer)
Pacinian corpuscles - deep pressure/vibration (in reticular layer)
Ruffini endings - stretch
Krause end bulbs - cold

3. Hypodermis / Subcutaneous Layer (Deepest Layer)

The hypodermis (also called subcutaneous tissue or superficial fascia) lies beneath the dermis. It is not technically part of the skin but is functionally connected to it.

Composed mainly of lobules of adipocytes separated by connective tissue septa
Also contains larger blood vessels, lymphatics, and nerve trunks
Functions in thermoregulation, energy storage, and cushioning
Thickness varies greatly with nutritional status and body region

Summary Table

Layer	Sub-layers	Origin	Main Contents	Function
Epidermis	4-5 strata	Ectoderm	Keratinocytes, melanocytes, Langerhans cells, Merkel cells	Barrier, UV protection, immune defense
Dermis	Papillary + Reticular	Mesoderm	Collagen, blood vessels, nerves, glands, hair follicles	Strength, sensation, nutrition
Hypodermis	-	Mesoderm	Adipocytes, vessels, nerves	Insulation, energy storage, cushioning

Sources: Junqueira's Basic Histology, Text and Atlas 17e, pp. 900-906; Histology: A Text and Atlas with Correlated Cell and Molecular Biology (Pawlina), pp. 1279-1293

Tell me about lungs

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I now have comprehensive material from Gray's Anatomy for Students to put together a thorough, well-illustrated answer. Here it is:

The Lungs

The lungs are the primary organs of respiration. There are two - one on either side of the mediastinum, each enclosed in its own pleural cavity. Their job is to bring air into close contact with blood so that oxygen is absorbed and carbon dioxide is expelled.

Anatomy of the right and left lungs showing surfaces, borders, and hilum

General Shape and Surfaces

Each lung has a half-cone shape with:

Apex - projects above rib I into the root of the neck
Base - sits on the diaphragm (diaphragmatic surface)
Costal surface - lies against the ribs and intercostal spaces
Mediastinal surface - faces the mediastinum and vertebral column; contains the hilum (the doorway where structures enter/leave the lung)
Three borders: inferior (sharp), anterior (sharp), and posterior (smooth and rounded)

The right lung is slightly larger than the left because the heart bulges more to the left.

Lobes and Fissures

Right lung showing superior, middle, and inferior lobes separated by the horizontal and oblique fissures, with key adjacent structures

Lung	Lobes	Fissures
Right	Superior, Middle, Inferior (3 lobes)	Oblique fissure + Horizontal fissure
Left	Superior, Inferior (2 lobes)	Oblique fissure only

The oblique fissure (both lungs) separates the inferior lobe from the superior and middle lobes
The horizontal fissure (right lung only) separates the superior from the middle lobe
The left lung has a tongue-like projection called the lingula that extends over the cardiac notch

The Hilum and Root

The root of the lung is a short tubular bundle of structures connecting the lung to the mediastinum. At the hilum, the following structures enter or exit:

1 pulmonary artery (superior)
2 pulmonary veins (inferior)
1 main bronchus (posterior)
Bronchial vessels, nerves, and lymphatics

The vagus nerve passes posterior to the root; the phrenic nerve passes anterior to it.

The Bronchial Tree

Bronchial tree from trachea to segmental bronchi and bronchopulmonary segments

The airway divides progressively:

Trachea (CVI to TIV/V) - held open by C-shaped cartilage rings; bifurcates at the carina
Main (primary) bronchi - right and left; the right is wider and more vertical, so inhaled foreign bodies lodge more often on the right
Lobar (secondary) bronchi - one per lobe (3 right, 2 left)
Segmental (tertiary) bronchi - supply bronchopulmonary segments
Bronchioles - no cartilage in their walls; further subdivide to supply alveoli

Bronchopulmonary segments: There are 10 segments per lung (some fuse in the left). Each is an independently functioning, cone-shaped unit of lung tissue supplied by a single segmental bronchus + pulmonary artery branch. They are the smallest surgically resectable unit of lung.

Blood Supply

Vessel	Carries	Direction
Pulmonary arteries	Deoxygenated blood	Right ventricle → lungs
Pulmonary veins	Oxygenated blood	Lungs → left atrium
Bronchial arteries	Oxygenated (nutritive) blood	Thoracic aorta → lung tissue itself

The pulmonary circulation is for gas exchange. The bronchial circulation nourishes the bronchial walls, large vessels, and visceral pleura.

Gas Exchange - The Alveoli

At the microscopic level, the terminal bronchioles open into alveolar ducts and then clusters of alveoli - tiny air sacs with extremely thin walls where gas exchange happens. The alveolar wall contains:

Type I pneumocytes - flat, thin cells forming ~95% of the alveolar surface; site of O₂/CO₂ exchange
Type II pneumocytes - secrete surfactant, which reduces surface tension and prevents alveolar collapse
Alveolar macrophages ("dust cells") - patrol the air spaces and phagocytose debris and pathogens

The blood-air barrier across which gas exchange occurs is only ~0.5 µm thick, consisting of: alveolar epithelium + basement membrane + capillary endothelium.

Key Functions of the Lungs

Function	Detail
Gas exchange	O₂ absorbed, CO₂ expelled at alveoli
Acid-base balance	Adjusting CO₂ levels regulates blood pH
Filtration	Removes small blood clots and emboli
Metabolism	Converts angiotensin I → angiotensin II (ACE in lung endothelium)
Immune defense	Alveolar macrophages, IgA secretion, mucociliary clearance
Vocalization	Provides air flow for speech

Clinical Relevance

Right lung is the more common site for inhaled foreign bodies and aspiration pneumonia (due to the wider, more vertical right main bronchus)
Bronchopulmonary segments guide surgeons in resecting diseased tissue while preserving healthy lung
Loss of surfactant (e.g., in premature infants) causes Respiratory Distress Syndrome (RDS)
The pleura (visceral + parietal layers) allows frictionless lung movement during breathing; breach causes pneumothorax

Sources: Gray's Anatomy for Students, pp. 205-211; Junqueira's Basic Histology 17e, pp. 901-903; Robbins & Kumar Basic Pathology

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