SENSORY ORGANS

Sensory organs are specialized organs that detect stimuli (touch, light, sound, smell, taste) and transmit signals to the central nervous system via sensory receptors.

FUNCTIONS OF SENSORY ORGANS

1. Detect environmental changes

2. Maintain body homeostasis

3. Protect body from danger

4. Help communication

5. Coordinate body functions

6. Maintain balance & posture

1. SKIN (Organ of Touch)

Structure of Skin

Skin is the largest organ of the body.

Surface area = 1.5–2 m²

Layers of Skin

1. Epidermis

Outer protective layer.

Cells:

• Keratinocytes

• Melanocytes

• Langerhans cells

Layers of epidermis:

1. Stratum corneum

2. Stratum lucidum (only palms & soles)

3. Stratum granulosum

4. Stratum spinosum

5. Stratum basale

Function:

• Protection

• Prevents water loss

• Melanin formation

2. Dermis

Contains:

• Blood vessels

• Nerve endings

• Hair follicles

• Sweat glands

• Sebaceous glands

Layers:

• Papillary layer

• Reticular layer

Function:

• Sensation

• Nourishment of epidermis

• Temperature regulation

3. Hypodermis (Subcutaneous tissue)

Contains:

• Fat

• Connective tissue

Function:

• Insulation

• Energy storage

• Shock absorption

Skin Appendages

1. Hair

2. Nails

3. Sweat glands

4. Sebaceous glands

Functions of Skin

• Protection

• Sensation

• Temperature regulation

• Excretion of waste

• Vitamin D synthesis

• Immune defense

Nursing Implications – Skin

• Prevent pressure ulcers

• Skin assessment (color, moisture)

• Wound dressing

• Burn management

• Infection prevention

• IV cannula site monitoring

• Maintain hygiene

• Patient turning schedule

2. EYE (Organ of Vision)

Structure of Eye

Diameter = 2.5 cm

Layers of Eyeball

1. Fibrous layer

• Sclera

• Cornea

2. Vascular layer (Uvea)

• Choroid

• Ciliary body

• Iris

3. Retina (nervous layer)

Contains photoreceptors:

• Rod cells – night vision

• Cone cells – color vision

Parts of Eye

Part	Function
Cornea	refracts light
Iris	controls pupil size
Pupil	regulates light entry
Lens	focuses image
Retina	image formation
Macula	central vision
Optic nerve	carries impulses
Aqueous humor	maintains pressure
Vitreous humor	maintains shape

Functions of Eye

• Vision

• Light perception

• Color detection

• Depth perception

Nursing Implications – Eye

• Visual acuity assessment

• Eye drop administration

• Prevent infection

• Cataract patient care

• Glaucoma monitoring

• Eye irrigation procedure

• Postoperative care

3. EAR (Organ of Hearing and Balance)

Structure of Ear

1. External ear

• Pinna

• External auditory canal

Function : Collects sound waves

2. Middle ear

Contains ossicles:

• Malleus

• Incus

• Stapes

Function : Amplifies sound vibrations

3. Inner ear

• Cochlea → hearing

• Vestibule → balance

• Semicircular canals → equilibrium

Functions of Ear

• Hearing

• Balance

• Position sense

Nursing Implications – Ear

• Hearing assessment

• Ear irrigation

• Ear drop administration

• Prevent infection

• Care for vertigo patients

• Post ear surgery care

4. NOSE (Organ of Smell)

Structure of Nose

Parts:

• External nose

• Nasal cavity

• Nasal septum

• Nasal conchae

• Olfactory receptors

• Olfactory nerve

Functions of Nose

• Smell sensation

• Filters dust particles

• Humidifies air

• Warms inspired air

Nursing Implications – Nose

• Oxygen therapy administration

• NG tube insertion

• Nasal suctioning

• Allergy care

• Epistaxis management

• Infection prevention

5. TONGUE (Organ of Taste)

Structure of Tongue

Muscular organ present in oral cavity.

Contains papillae:

1. Filiform papillae

2. Fungiform papillae

3. Circumvallate papillae

4. Foliate papillae

Taste Sensations

• Sweet

• Sour

• Salty

• Bitter

• Umami

Functions of Tongue

• Taste sensation

• Speech

• Swallowing

• Chewing assistance

Nursing Implications – Tongue

• Oral hygiene care

• Nutritional assessment

• Detect dehydration

• Identify vitamin deficiency

• Assist feeding patient

• Detect oral infection

• Monitor tongue color changes

SUMMARY TABLE

Organ	Structure importance	Nursing importance
Skin	protective layers	wound care
Eye	retina & lens	vision care
Ear	cochlea	hearing care
Nose	olfactory cells	oxygen therapy
Tongue	taste buds	oral care