Download MBBS Integumentary System Skin Lecture PPT

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? Skin and its derivatives (hair and nail).
Skin is outer covering of body.
Largest organ of body (16% of body weight).
? Consists of epidermis and dermis
? Epidermis is covered by keratinized stratified

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squamous epithelium

? Dermis consists of irregular connective tissue
? Beneath the dermis is hypodermis or a subcutaneous

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layer of connective tissue and adipose tissue that

forms the superficial fascia.

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FUNCTION OF SKIN

? Protection- from injury.
? It provides a barrier to water.
? Thermoregulation-- sweating

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? Sensory perception- like pain, touch,

temperature and pressure.

? Helps in production of vit.D.

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? Excretions through sweat of water, sodium

salts, and nitrogenous waste.
? TYPES OF SKIN--
? Thick skin--Skin on the surface of palm and sole.

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? Epidermis is thicker than elsewhere.
? Thick skin is hairless.
? Thin skin--present other places of body except

palm and sole.

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? Thin and hairy.
? MICROSCOPIC STRUCTURE OF SKIN--
? Skin consist of two layers-
? Epidermis

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? Dermis
? EPIDERMIS--
? It consist of stratified squamous epithelium.
? Five layers in thick skin from deep to superficial.
i)Stratum basale

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ii)Stratum spinosum
iii)Stratum granulosum
iv)Stratum lucidum
v)Stratum corneum

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? Stratum Basale (Germinativum)--
- Deepest layer of epidermis
-Single layer of cuboidal cells that rests on the

basement membrane.

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- Cells attached by desmosomes and by

hemidesmosomes to basement membrane.

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-The newly produced cells move towards

superficial layer

? Stratum spinosum--

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? Consist of several layers of polygonal cells.

? During histological preparation, cells shrink

and intercellular spaces appear as spines

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? This layer well developed in friction and

pressure area of skin.
? Stratum granulosum--

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? Consists of 3-5 layers of flattened fusiform cells.
? These cells are filled with keratohyalin granules.

? Stratum lucidum--
? Seen only in thick skin.

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? Cells are flattened, translucent.
? These cells are filled with protein called keratin

and eleidin.
? Stratum corneum--

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? Most superficial layer of epidermis.
? Composed of dehydrated dead cells.
? Cells are filled with keratin.
? Thickness is much more in thick skin.
? This layer is continuously sloughed off, this

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process takes 20-30 days.
? DERMIS--
? Made up of collagen bundles.
? It also contains elastic fibres, nerves, lymphatics

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and blood vessels.

? It is divided into two layers.
? Papillary layer

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? Reticular layer

? Papillary layer--
? Narrow band of loose connective tissue in

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contact with basement membrane of st. basale.

? Shows finger-like processes (dermal papilla)

projecting into under surface of epidermis.

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? Papilla contain type III collagen, elastic fibres,

nerves, blood vessels and connective tissue cells.
? Reticular layer--

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? It contains bundles of type I collagen, thick

elastic fibres, nerves, blood vessels and few

connective tissue cells

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CELLS OF EPIDERMIS

? Keratinocytes--
? Most abundant cell (90%).
? Produces keratin

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? Keratinocytes migrates from stratum basale

towards surface.
? Melanocytes--
? Derived from neural crest cells.

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? Located between st. basale and st. Spinosum.
? Produce melanin pigments (responsible for skin

colour).

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? Melanin darkens skin colour and protect it from

ultraviolet radiation.

? In white people melanin is degraded by

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lysosomes.

? In black people this pigment is more stable.

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? Langerhans Cells--
--Found in st. spinosum; part of immune system of

body

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--Are antigen-presenting cells of the skin.

? Merkel's Cells--
--Sensory cells present in the st. Basale .
--Derived from neural crest.

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--Function as mechanoreceptors.
--Abundant in fingertips, oral mucosa and hair follicle
DIFFERENCE BETWEEN THIN AND THICK SKIN

THIN SKIN

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THICK SKIN

LAYERS OF EPIDERMIS ST. LUCIDUM ABSENT PRESENT

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THICKNESS OF

0.10-0.15 mm

0.6-4.5 mm

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EPIDERMIS
HAIR FOLLICLES

PRESENT

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ABSENT

SWEAT GLAND

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FEW

MANY

SENSORY RECEPTOR

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LESS

MORE

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DISTRIBUTION

COVERS ALL THE

PALM AND SOLE

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PARTS OF THE BODY

EXCEPT PALM AND

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SOLE


THIN SKIN

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THICK SKIN


GLANDS OF SKIN

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? Sebaceous Gland
? Present in the dermis of skin.
? Simple acinar gland whose

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duct opens into the hair

follicle.

? It secretes oily substance

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called sebum.

? Sebum keeps the skin smooth

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to prevent it from drying

? Mode of secretion is

holocrine.

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? Sweat Gland
? Present in the deeper part of

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dermis and is widely distributed.

? Simple coiled, tubular gland

whose duct opens on the

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epidermal surface.

? watery secretion helps in

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maintaining body temperature.
? Two types of sweat glands

? Eccrine:
Widely distributed throughout skin.

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Densely in the palms and soles.
Watery secretion.

? Apocrine:
Found in axilla, groin areola of breast.

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Thick viscous secretion


RESPIRATOTY SYSTEM
INTRODUCTION

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? Consists of nose, pharynx, larynx, trachea and

lungs.

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? Functions:--
? Perception of smell
? Filtration of inhaled air
? Phonation
? Respiration

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? Maintenance of blood pH
? Functionally respiratory system consists of two

parts.

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? Conducting part--
? Nasal cavity
? Pharynx
? Larynx
? Trachea

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? Bronchi
? Bronchioles & terminal bronchioles.
? Respiratory part--
? Respiratory bronchioles
? Alveolar duct

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? Alveolar sac & alveoli.
Conducting part

? General structure of the conducting part
? Respiratory tract made of four coats--

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1.Mucosa--epitehelial lining and underlying lamina

propria.

Epithelium is usually pseudostratified ciliated

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columnar with goblet cells.

2.Submucosa--layer of loose connective tissue

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containing mixed gland.

3.cartilage layer--mostly hyaline cartilage and

smooth muscle.

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4.Adventitia--fibroelastic connective tissue.
? Epiglottis--
? Consists of a plate of elastic cartilage.
? On the both sides of cartilage there is

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presence of lamina propria.

? Lamina propria contains seromucous gland.
? Anterior surface & upper part of posterior

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surface lined by stratified squamous

epithelium.

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? Posterior surface lined by pseudostratified

ciliated columnar epithelium with goblet cells.

? Trachea--

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? The wall of the trachea consists of mucosa,

submucosa, hyaline cartilage, and adventitia.

? Trachea is kept patent (open) by 16-20 C-

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shaped hyaline cartilage rings.

? The gap between the posterior ends of the

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hyaline cartilage is filled by the smooth

trachealis muscle.

? The lumen of the trachea is lined by

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pseudostratified ciliated columnar epithelium

with goblet cells.

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Respiratory part

? Respiratory bronchioles--

? Transition from conducting part to respiratory part.

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? Less than 0.5mm diameter.
? Lining epithelium is simple cuboidal with cilia.
? Alveoli--

? Thin walled polyhedral sacs about 200 um in

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diameter.

? Alveoli are closlely packed, so the alveolar wall is a

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partition or septum between two alveoli.

? Interalveolar septa contains network of capillaries.
? There may be opening in septa called as pores.
? Lined by simple squamous epithelium.

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? Blood-air barrier--
? The air in alveolus is separated from blood in

capillary by three structures.

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? Endothelium of capillary
? Lining epithelium of alveolus
? Fused basal lamina of endothelium and

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epithelium.

? This is thin (1.5-2 um) and facilitates the

diffusion of oxygen and carbon dioxide.

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? Cells of alveolar wall--
? Type I alveolar cells (pneumocyte I)
? Very thin squamous cells
? Cover 95% of alveolar surface

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? Type II alveolar cells (pneumocyte II)
? Large rounded cells contains microvilli
? Secretory in nature and secretes pulmonary

surfactant, which lower surface tension and

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prevents alveoli from collapsing during expiration

? Type II alveolar cells also gives type I alveolar cells
? It also produces surfactant protein A, B, C and D

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? Brush cells--
? These cells found occasiniolly in alveolar epithelium.
? Serve as receptor to monitor the quality of air

entering in lung.

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? Alveolar macrophage--
? Found in connective tissue of interalveolar septa
? First line defence against pulmonary infection.
? They phagocytes dust particles so called as dust cells.

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? In patients of heart failure the erythrocytes

accumulate in alveoli which is phagocytosed by

macrophage and acquire brick red colour so called as

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heart failure cells.
Difference between Bronchus & Bronchiole

BRONCHUS

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BRONCHIOLE

DIAMETER > 1 MM

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DIAMETER< 1 MM

PSEUDOSTRATIFIED CILIATED SIMPLE COLUMNAR OR

COLUMNAR

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SIMPLE CUBOIDAL

SMOOTH MUSCLE

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SMOOTH MUSCLE & ELASTIC

FIBRES

CARTILAGE PRESENT

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CARTILAGE ABSENT

GLANDS PRESENT

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NO GLANDS