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Cont…
Objectives
• After completion of this module you will be able to:

 Describe the structure and location of bones in the body

Musculoskeletal System  Describe the structure and location of muscles in the

body

 Define terms related to bone structure, joints, and joint

movements

 Define terms related to structure of muscles

Cont…. Cont….
Function
• The musculoskeletal system is - Give shape and structure to the body
made up of: - provide support
- Bones (the skeleton) - Allow movement
- Cartilage - Protect internal organs
- Tendons - Store calcium and other minerals
- ligaments, - Produce certain blood cells
- Produce heat
- Joints
- Muscles
• subdivided into two broad systems:
- other connective tissues
 Skeletal system
 Muscular system

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Skeletal system Cont….

• is all the bony tissues in the • The skeleton has ~206 bones
body Axial skeleton
• Skull
 Components of the skeletal
Cranium = 8
system Face = 14
- Bones
- Joints • Hyoid =1
• Auditory ossicles = 6
- Cartilages • Vertebral column = 26
- Ligaments
- tendon • Thorax
Sternum =1
Ribs = 24

Subtotal = 80

Cont…. • Pelvic ( hip) girdle Cont….

Appendicular skeleton Hip( plevic bone) =2
• Pectoral (shoulder) girdles
Clavicle = 2 • Lower limbs
Scapula = 2 Femur = 2
Patella = 2
• Upper limbs Fibula = 2
Humerus =2 Tibia =2
Ulna =2 Tarsals = 14
Radius =2 Metatarsals = 10
Carpals = 16 Phalanges = 28
Metacarpals = 10 subtotal = 126
phalanges = 28 • Total in the adult skeleton = Axial skeleton
80 + Appendicular skeleton 126 = 206

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Microscopic Anatomy of Bone Cont….

• Osteon (Haversian System)
- A unit of bone Bone Cells
• Central (Haversian) canal
• Osteocytes
- Opening in the center of an
osteon - Mature bone cells
- Carries blood vessels and - Contained with in the
nerves spaces in the bone matrix
called lacunae
• Perforating (Volkman’s) canal - extends numerous
- Canal perpendicular to the processes into small
central canal tunnels called canaliculi
- Carries blood vessels and
nerves

Cont….

• Osteoclasts
- bone-resorbing cells
present on bone surfaces
- Bone-destroying cells
- Break down bone matrix
for remodeling and Classification of bones
release of calcium.
 Bone remodeling is a
process by both
osteoblasts and
osteoclasts

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According to their Location Pectoral Girdles

• Divided into two: • Shoulder Girdles
I. Axial Skeleton • consist of the clavicles and the
scapulae
II. Appendicular Skeleton
• attach the upper limbs to the axial
skeleton
I. Appendicular Skeleton • provide attachment points for
• is made up of the bones of the muscles that move the upper
limbs and their girdles limbs
• articulates with the axial skeleton
only at the sternoclavicular joint,
 Pectoral girdles attach the upper allowing great mobility.
limbs to the body trunk • supported, stabilized, and moved
 Pelvic girdle secures the lower by axio appendicular muscles
limbs

Bones of the upper limb

• Each upper limb consists Humerus
of 30 bones
- humerus = in the arm • Is the largest bone in
- ulna and radius = in the the upper limb
forearm
- 8 carpals = wrist bones • articulates with the
- 5 metacarpals = palm scapula,
bones
-at glenohumeral joint
- 14 phalanges = finger
bones in the hand - the radius and ulna at
the elbow joint.

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Bones of Forearm Bones of Hand

• are the radius and ulna
• They articulate proximally with the • Skeleton of the hand
humerus and distally with the wrist contains wrist bones
bones
( 8 carpals), bones of
• They also articulate with each the palm
other proximally and distally at
small radioulnar joints
(metacarpals), and
bones of the fingers
• Interosseous membrane connects
the two bones along their entire (phalanges)
length

Cont… Cont…
• Carpal bones are • From lateral to medial,
arranged in proximal
and distal rows of four. the four carpal bones
in the distal row are
• From lateral to medial,
the four carpal bones the:
in the proximal row - Trapezium
are: - Trapezoid
- Scaphoid - Capitate
- Lunate - Hamate
- Triquetrum
- Pisiform

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Pelvic (hip) girdle

• consists of the two hip bones,
also called coxal bones
• hip bones of a newborn is
composed of three parts: the
ilium, the pubis, and the
ischium
• Mature hip bone is formed by
the fusion of these three
primary bones at the end of
the teenage years

Ilium
• forms the largest part
of the hip bone
Structural futures:
- alae, body of the ilium,
anterior superior and
anterior inferior iliac
spines, iliac crest, gluteal
lines, iliac fossa

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• forms the postero- Ischium

inferior part of the hip
bone
• Its ramus joins the
inferior ramus of the
pubis to form the
ischiopubic ramus.
• Posteriorly forms the
inferior margin greater
sciatic notch.
• Structral futures:
ischial spine, lesser
sciatic notch, ischial
tuberosity.

Bones of the lower limb

Pubis
• Each lower limb is
• forms the composed of 30 bones:
anteromedial part of - femur = in the thigh
the hip bone. - patella = kneecap
Structural futures: - tibia and fibula = in the
leg
-body, superior and
- 7 tarsals = ankle bones
inferior rami, pubic
- 5 metatarsals
tubercles, pecten pubis.
- 14 phalanges = toes in the
foot

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Thigh bone Bones of leg

• Femur • Tibia and Fibula
• is the longest and heaviest • The tibia articulates with the
bone in the body. condyles of the femur superiorly
• It transmits body weight and the talus inferiorly.
from the hip bone to the
tibia when a person is • The fibula mainly functions as an
standing. attachment
for muscles,
• consists of a shaft , - but it is also important for the
proximal and distal ends. stability of
• The proximal end of the the ankle joint.
femur consists of a head, • The shafts of the tibia and fibula
neck, and two trochanters are connected
- greater and lesser. by a dense interosseous membrane

Bones of Foot Cont…

• include the tarsus, • The metatarsus
metatarsus, and consists of five
phalanges. metatarsals that are
• There are 7 tarsal numbered from the
bones, 5 metatarsal medial side.
bones, and 14
phalanges.
• The tarsus consists • There are 14
of: talus, calcaneus, phalanges.
cuboid, navicular,
and three
cuneiforms.

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Axial Skeleton
Axial Skeleton • Forms the longitudinal
part of the body
• Divided into three parts
- Skull
- Vertebral column
- Bony thorax

Vertebral Column .
• Consists of 33 vertebrae arranged in five
• The vertebrae in the vertebral column
regions:
are separated by resilient IV discs
- 7 cervical
• Significant motion occurs only b/n the
- 12 thoracic
- 5 lumbar 25 superior vertebrae
- 5 sacral • Each vertebrae is given a name
- 4 coccygeal according to its location
• sacral vertebrae fuse to form sacrum

• coccygeal vertebrae fuse to form coccyx

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Cont…. Cervical Vertebrae

• skeleton of the neck

basic structure of vertebrae • Located b/n the cranium

and thoracic vertebrae
• A typical vertebra consists
of: • oval transverse foramen
is their distinctive feature
- vertebral body
• Vertebrae C3–C7 are
- a vertebral arch
typical cervical vertebrae
- seven processes
• vertebrae C1 and C2 are
atypical

Vertebra C1 (atlas) .
- has neither a body nor a spinous process

- articulations b/n the superior articular surfaces of the lateral

masses of the atlas and the occipital condyles known as
Atlanto-occipital Joints

- These joints permit nodding of the head indicating the “yes”

movement

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Vertebra C2(axis) .

- Is strongest

- The odontoid process is It’s

distinguishing feature

- Atlanto-axial Joints b/n C1

and C2 permits the head to
be turned from side to side
to indicate the “no”
movement

Thoracic Vertebrae
- 12 bones in the region of
Lumbar vertebrae
thorax • Are b/n the thorax
- increase in size from T1 to and sacrum.
T12
- serve as attachment for
• are the largest
the ribs
vertebrae of the
- have extra articular process
for attachment of ribs
column.
- have long spinous
processes that slope • have large bodies,
obliquely downward and thick processes

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Sacral vertebrae
• 5 fused vertebrae
• is located between the
hip bones
• provides sacroiliac
joint

Coccyx Hyoid bone

• Lies in the anterior part of
the neck at the level of the
• called the tail bone
C3 vertebra.
• composed of 4 or 5
fused vertebrae • U-shaped bone suspended
by muscles.

• Does not articulate with

any other bone

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Skull (cranium) Cont….

• is the skeleton of the head • in adults is formed by a
series of eight bones
• Has two parts:
1. Neurocranium
• bony case of:
- Brain
- cranial meninges
- proximal parts of the cranial
nerves
- the vasculature of the brain

Cont….
• Frontal bone : forms
anterior roof of cranium,
nasal cavity & orbit
• Parietal bone: separated
from frontal bone by
coronal suture
• Occipital bone: forms the
back & much of the base
of the skull
• Temporal bone: forms
lower sides of the
cranium

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Cont….
• Sphenoid bone: keystone Human Skull, Superior View
bone (all other bones
articulate with it)
- shaped like bat with
outstretched wings
- completes sides of skull
and contributes to orbits
• Ethmoid bone: lies in
front of sphenoid
- forms orbits and nasal
septum

Cont….
2. Viscerocranium (facial
skeleton)
• consists of 15 irregular
bones

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Unique Features of the Skull

A. Sutures
• immovable joints in most cases
in an adult
• holds skull bones together
I. Coronal suture
- unites the frontal bone and two
parietal bones

II. Sagittal suture

- unites the two parietal bones

Cont…. Cont….
III. Lambdoid suture B. Paranasal sinuses
- unites the parietal bones to the • Paired cavities, near the
occipital bone nasal cavity
• Include frontal sinus,
IV. Squamous sutures : sphenoid sinus, ethmoidal
- unite the parietal bones to the sinuses, and maxillary
temporal bone sinuses
- produce mucus
- serve as resonating chambers
- lighten the weight of the
skull

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Cont…. Auditory Ossicles

C. Fontanels • form a mobile chain of small
• found b/n cranial bones at birth bones across the tympanic
• include anterior fontanel, posterior cavity from the tympanic
fontanel, anterolateral fontanels, and membrane to the oval
posterolateral fontanels window
- enable the fetal skull to be • Three auditory ossicles in the
compressed as it passes through the middle ear of each ear
birth canal - mallus
- permit rapid growth of the brain - incus
during infancy - stapes
• Helps to transmit sound
impulses

Bony Thorax Cont….

Ribs
• Forms a cage to protect
• 12 pairs (connect directly
major organs to thoracic vertebrae in
the back)
• Made-up of three parts • 7 pairs “true ribs”
connect directly to
- Sternum sternum anteriorly
• the remaining 5 pairs are
- Ribs called "false ribs”
• last 2 pairs “floating ribs”
- Thoracic vertebrae
do not attach to sternum
at all

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Cont….
Sternum
• Flat bone located
anteriorly
• Has 3 fused bones:
manubrium, body &
xiphoid process
• On its side, it has costal &
clavicular notches and
superiorly jugular notch
• Sternal angle is palpated
between manubrium &
body

II. According to their Structural Appearances

i. Compact (Dense) Bone

ii. Spongy( trabecular,
cancellous) Bone
- distinguished by the
relative amount of solid
matter
- by the number and size of
the spaces they contain

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Cont…. III. According to their Shapes

 Compact bone  Long Bones
- Have Outer dense layer that - Typically longer than wide
looks smooth and homogenous - Have a shaft with heads at
both ends
to the naked eye.
- Contain mostly compact
- Have medullary cavity. bone
- are tubular
 Spongy Bone Examples: Femur, humerus
- Inner layer composed of small  Short Bones
needle like spicules of bone and - Generally cube-shape
numerous opening having a - Contain mostly spongy
spongy appearance to the bone
naked eye. Examples: Carpals,
tarsals

 Flat Bones Cont…. Cont….

- Thin and flattened  Sesamoid bones
- Usually curved - Develop in certain
- Thin layers of compact bone tendons
around a layer of spongy bone. - found where tendons
Examples: Skull, ribs, cross the ends of long
sternum
bones in the limbs.
 Irregular Bones
- they protect the tendons
- Irregular shape
from excessive wear
- have various shapes other than
long, short, or flat. Examples: the patella or
- Do not fit into other bone knee cap
classification categories.
Example: Vertebrae and hip

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Gross Anatomy of a Long Bone Cont….

• Diaphysis
- Shaft - Made of hyaline cartilage
- Composed of compact bone - Decreases friction at joint
surfaces
• Epiphysis
- Ends of the bone • Medullary cavity
- Composed mostly of spongy bone - Cavity of the shaft
- Contains red marrow (for blood
• Articular cartilage cell formation) in infants
- Covers the external surface of the
epiphyses

Bone Markings Cartilage

• Surface features of bones • connective tissue composed of
• Sites of attachments for chondrocytes and
muscles, tendons, and extracellular matrix
ligaments • Unlike rigid bone, cartilage has
• Passages for nerves and blood the flexibility of firm plastic
vessels
• Categories of bone markings • Three types:
• Projections and processes:  Fibrous cartilage
grow out from the bone - forms at the meniscus and the
surface. inter- vertebral disks
• Depressions or cavities:
indentations

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Cont…. Joints
 Hyaline cartilage • Articulations
- covers articular bone surfaces
(where one or more bones • point of contact:
meet at a joint), connects the
- b/n bones
ribs and sternum, and appears
in the trachea, bronchi, and - b/n cartilage and bones
nasal septum
- b/n teeth and bones
 Elastic cartilage • Classified:
- located in the auditory canal,
external ear ,and epiglottis

Functionally Cont…. Muscular system

• consists of all the muscles
• Synarthroses = immovable joints of the body
• Amphiarthroses = slightly moveable • Constitutes ≈half of
joints body’s weight
• Diarthroses = freely moveable joints • Skeletal muscle about
40% of body weight in
men & 32% in women
Structurally • consists of about 600
• Fibrous joints = Generally immovable muscles
• Cartilaginous joints
- Immovable or slightly moveable
• Synovial joints = Freely moveable

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Cont…. Types of muscle tissue

 Movement • Based on striations
muscles could be:
 Maintaince of posture Striated or Non-striated
• Based on location can be
 Heat production
classified as:
(thermogenesis)
Skeletal, Cardiac &
 Stabilization of joints Smooth muscles
• Based on function:
Voluntary VS Involuntary

Skeletal Muscles Connective Tissue Investment of Muscles

• composed of hundreds to • Endomysium: cover the
thousands of cells, which
individual muscle fibers
are called muscle fibers

a. proximal attachment = • Perimysium: binds groups

origin of a muscle of fibers together into
b. The more movable (that
bundles called fasiculi
moves most) = distal
attachment = insertion
of a muscle
• Epimysium: covers the
entire muscle

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Muscle Architecture Cont….

1. Parallel: 3. Convergent:
- Fascicles parallel to - fan-shaped muscles.
longitudinal axis of E.g. deltoid
muscle; terminate at 4. Pennate:
either end in flat. - feather shaped
- E.g. sartorius - muscles have many
2. Sphincter: fibers per unit area & are
- surround a body strong muscles
opening or orifice. (unipennate, bipennate
- E.g. orbicularis oris & multipennate)

Nerves and Blood vessels Cont….

• muscle tissue of the
• In general, each skeletal muscle is supplied by heart wall
one nerve, one artery &one or more veins • involuntary muscle
• Each muscle fiber in a skeletal muscle is • Contraction pumps blood
contacted by one nerve ending, which signals through the blood vessels
the fiber to contract such a contact is called • striated
neuromuscular junction. • muscle fibers are
branched longitudinally
• A skeletal muscle fiber cannot contract unless it
is stimulated by a nerve impulse

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Cont…. Smooth muscle

• Ends of adjacent cells are
connected through an • Found in the walls of
intercellular junctional visceral organs such as
complex called the the GIT, respiratory tubes,
intercalated disc urinary bladder, uterus
• spindle shaped cell
• contain one or two • one centrally located
centrally located nuclei nucleus
• non-striated
• actively divide and
regenerate

Naming of muscles Cont….

1. according to their 3. according to their shape
function - Deltoid E.g. Deltoid
- Flexor E.g. Flexor - Serratus E.g.Serratus
carpi radialis anterior
- Adductor E.g. Adductor 4. according to orientation
longus of fibers
2. according to their - Rectus E.g. rectus
attachment abdominis
- Scm - Transverse E.g.
- Sternothyroid transverse abdominis

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Cont…. Cont….
5. according to their relative 7. according to relative
size position
- Maximus E.g. gluteus - Medial
maximus
- internal
- Longus E.g flexor
8. Naming with a
digitorum longus
combination of criteria
• flexor carpi radialis longus
6. according to the number of
heads • extensor digiti minimi
- biceps brachi
- triceps brachi
- quadriceps

Functions of muscles Distribution of skeletal muscles

• Muscles serve specific
functions in moving and muscles of the axial skeleton
positioning the body
I. prime mover (agonist) • responsible for facial expression, mastication, eye
- is the main muscle movement, tongue movement, respiration; and
responsible for producing a
specific movement of the those of the abdominal wall and the pelvic outlet.
body muscles of the appendicular skeleton
II. synergist • Includes muscles of the pectoral girdle, arm,
- complements the action of forearm, wrist, hand, pelvic girdle, thigh, leg and
a prime mover
foot
III. antagonist
- is a muscle that opposes the
action of another muscle

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Muscles of the Axial Skeleton Cont….

I. Muscles of Facial
Expression
• social communication.
• their origins are in the
fascia or in the bones of
the skull, with insertions
into the skin
• don’t move the facial
skeleton.
• receive their motor
innervations from the
facial nerve (CN VII)

II. Muscles Of Mastication III. Ocular Muscles

• Two types of muscles are
• Are muscles that move associated with the
the mandible eyeball,
• assist in speech - Extrinsic
• innervated by mandibular - intrinsic
branch of trigeminal • Extrinsic muscles
nerve. originate outside the
eyeball
and are inserted on its
outer surface
- They move the eyeballs in
various directions.

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Cont…. IV. Muscles of the Tongue

- They move the eyeballs in • the intrinsic and
various directions extrinsic muscles

• Intrinsic muscles originate • supplied by hypoglossal

and insert entirely within nerve (CN XII) except
the eyeball the palatoglossus,

- They move structures - which is supplied by the

within the eyeballs, such as pharyngeal branch of
the iris and the lens. vagus nerve (CN X)

Cont…. V. Muscles of the Neck

1. Superficial Neck Muscles
• four intrinsic and extrinsic 2. Muscles of anterior
muscles in each half of cervical region
the tongue are separated by  Suprahyoid muscles
lingual septum  Infrahyoid muscles

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Cont…. VI. Muscles of Respiration

3. Prevertebral muscles • Pectoralis major
• Are the anterior and • Serratus anterior
lateral vertebral muscles • Serratus posterior
• External intercostal
• Internal intercostal
• Innermost intercostal
• Transversus thoracis
• Diaphragm

VIII. Muscles of the Pelvic Outlet

VII. Muscles of the Abdominal Wall • Pelvic outlet supports the
pelvic viscera
• Rectus abdominis • Consists of levator ani &
• Transverse coccygeus muscles
together called pelvic
abdominis diaphragm
• Internal and • Perineal muscles are
• external oblique positioned inferior to the
abdominis pelvic diaphragm
• Innervated by pudendal
• pyramidalis
nerve

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1. Back muscles Cont….

i. Superficial extrinsic back ii. intrinsic back
muscles muscles
• are posterior axio- • splenius muscles
appendicular • erector spinae
• Trapezius muscles
• latissimus dorsi • transversospinalis
muscle group
• levator scapulae
• rhomboids

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iii. Scapulohumeral
Cont….
(intrinsic shoulder)
muscles:
• Deltoid
• teres major
- four rotator cuff
muscles
• Supraspinatus
• Infraspinatus
• teres minor,
• subscapularis

iv. anterior axio -

Cont…. 2. Arm muscles
appendicular muscles i. Anterior compartment
• move the pectoral girdle - biceps brachii
• Pectoralis major - Brachialis
• pectoralis minor - Coracobrachialis
• Subclavius
• serratus anterior ii. posterior compartment
- triceps brachii

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3. Muscles of Forearm Cont….

1. flexor/pronator muscles
A. superficial layer
- pronator teres 2. Extensor muscles
- flexor carpi radialis - extensor carpi radialis
- palmaris longus longus
- flexor carpi ulnaris
- extensor carpi
B. intermediate layer radialis brevis
- flexor digitorum superficialis - extensor carpi ulnaris

C. deep layer
- flexor digitorum profundus
- flexor pollicis longus
- pronator quadratus

4. Muscles of Hand
• Thenar muscles in the thenar compartment:
- abductor pollicis brevis, flexor pollicis brevis, and opponens
pollicis

• Adductor pollicis in the adductor compartment

• Hypothenar muscles in the hypothenar compartment:

- abductor digiti minimi, flexor digiti minimi brevis, and
opponens digiti minimi

• Short muscles of the hand, the lumbricals, in the central

compartment with the long flexor tendons.

• The interossei in separate interosseous compartments

between the metacarpals

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Muscles of the thigh Anterior Thigh Muscles

• flexors of the hip and
• Originated from the pelvic girdle & inserted to different sites on extensors of the knee
the femur
• Stabilize a highly movable hip joint
• include the :
• Provide support for the body during bipedal stand and
locomotion  Pectineus
• The muscles are divided in to  Iliopsoas
 Anterior  Sartorius
 posterior
 quadriceps femoris
 and medial groups

• Generally innervated by
the femoral nerve

Medial thigh muscles

• Comprise the adductor
group

• consisting of the:
 adductor longus
 adductor brevis
 adductor magnus
 Gracilis
 Obturator externus

• All except the “hamstring

part” of the adductor
magnus and part of the
pectineus are supplied by
the obturator nerve

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Muscles of the gluteal region

• are organized into two
layers
I. superficial layer of muscles
of the gluteal region
• consists of
 Gluteus maximus
 Gluteus medius
 Gluteus minimus
 Tensor fasciaelatae

Cont….
II. deep layer of muscles of
the gluteal region
• consists of:
 Piriformis
 obturator internus
 Superior and inferior
gemelli,
 quadratus femoris

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Posterior thigh muscles

• Are extensors of hip
and flexors of knee
• Include:
 Semitendinosus
 Semimembranosus
 Biceps femoris
• Generally
innervated by the
tibial portion of the
sciatic nerve

Muscles of the leg

Muscles of anterior
compartment of leg
• Are the
 tibialis anterior
 extensor digitorum
longus
 extensor hallucis longus
 fibularis tertius
• Innervated by deep
fibular nerve

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Cont…. Cont….
Muscles in lateral Muscles in posterior
compartment of leg compartment of the leg
• contains the: • divided into superfi cial and
deep subcompartments/
 fibularis longus
muscle groups
 brevis muscles • Innervated by the tibial
• Innervated by the nerve
superficial fibular nerve I. Superficial muscle group in
posterior leg compartment
• includes the :
 Gastrocnemius
 Soleus
 plantaris

Cont….
II. Deep muscle group in
posterior compartment
• Include:
 Popliteus
 flexor digitorum longus
 flexor hallucis longus
 tibialis posterior

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Muscles of Foot
• Muscles on the dorsum of
foot
• Include:
 Extensor digitorum brevis
 Extensor hallucis brevis
• Innervated by deep
fibular nerve

Cont…. Cont….
• muscles on the foot the 3rd layer
sole  Flexor hallucis brevis
1st layer  Adductor hallucis
 Abductor hallucis  Flexor digit minimi brevis
 Flexor digitorum brevis
 Abductor digiti minimi 4th layer
 Plantar interossei
2nd layer  Dorsal interossei
 Quadratus plantae
 Lumbricals

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The integumentary system

• Include the skin and its

derivatives
- sweat glands
- sebaceous glands
- Hairs
- nails

Functions of the integumentary system

- Protection

- temperature homeostasis

- Receives stimuli

- Excretion

- Synthesis of Vitamin D

- Reservoir for Blood

- nonverbal communication

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Skin Cont…. Cont….

I. Epidermis
• is the largest single organ of • Outermost superficial region
the body
• account 15–20% of total body • Composed of epithelial cells
weight • Avascular
• Consists of: • Composed of keratinized
I. Epidermis stratified squamous epithelium,
II. Dermis consisting of 4 distinct cell types
and 4 or 5 layers
 Hypodermis
- beneath the dermis which
attaches the dermis to the • Cell types include: keratinocytes,
underlying structures melanocytes, Merkel cells, and
- not part of the skin but has
close association with it Langerhans’ cells

• Keratinocytes: most cells in epidermis Cont….

synthesize keratin
• Melanocytes: in the deepest layer
synthesize pigment melanin
• Merkel cells: touch receptors, attached
to nerve cell
• dentritic cells(Langerhans cells): are
macrophages that stand guard against
toxins, microbes and other pathogens
that penetrate the skin

- if detected they alert immune system

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Layers of the Epidermis Cont….

1. basal layer (stratum basale)
• Deepest layer firmly
attached to the Dermis
• Consists of a single row of basophilic
columnar or cuboidal cells
• Characterized by intense mitotic
activity
• Responsible for constant production
of epidermal cells in conjunction
with the initial portion of the next
layer

• Melanocytes and Merkel cells are Cont…. Cont….

• Melanin granules and Langerhans’
present cells are abundant in this layer
2. Spinous layer (stratum spinosum) 3. The granular layer (stratum
granulosum)
• thickest epidermal layer • consists of 3–5 layers of
flattened polygonal cells
• Mitosis is less frequent than in the undergoing terminal
stratum basale differentiation

• Just above the basal layer some cells may

• as cells move up from s. basale they
still divide and this, die & get flatter,
- combined zone is called the stratum - and Keratinization begins in this
layer
germinativum

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4. Stratum lucidum Cont…. Cont….

- only seen in thick skin • Thick skin is found on the
- translucent layer of extremely palm, fingertips, and soles of
flattened eosinophilic cells the feet.
5. Stratum corneum
• consists of 15–20 layers of • Thin skin is found on the
flattened, nonnucleated rest of the body where the,
keratinized cells • - stratum lucidum is absent
• The cells are continuously shed and and the other 4 layers are
replaced by cells that move up thinner.
from the lower layers
• protects the lower layers of the
epidermis from water loss and
chemical, physical and biological
damage

Dermis
• located below the basement membrane
• binds to the hypodermis
• has a rich supply of blood vessels, nerve
fibers, sense receptors and lymphatic
vessels
• Thickness varies according to the
region of the body, and reaches its
maximum of 4 mm on the back
• Hair follicles, sebaceous glands, and
sweat glands are found in the dermis, but
they are produced by cells from the
epidermis
• composed ofthe papillary and reticular
layers

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Hypodermis Hair
• Deepest region / subcutaneous • Present on all skin surfaces except
the palms, soles, lips, nipples and
• Also called the superficial facia
parts of external reproductive
(superficial to the facia of the skeletal
organs
muscles)
• Extend from skin surface into the
• Consists mostly of connective tissue
dermis and contain the hair root
• Anchors the skin to the underlying • Hair is composed of dead
muscle but loosely enough that epidermal cells
the skin can slide freely
• contains fat cells that vary in number • Arrector pili muscle (bundle
in different regions of the body and of smooth muscle cells)
vary in size according to nutritional attaches to each hair follicle
state • Hairs grow discontinuously,
with periods of growth
followed by periods of rest

Structure of nail
• Scale like modification of the epidernmis on ther distal,
dorsal surface of the fingers and toes

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Glands of the skin • Found over entire surface of Cont….

 Sebaceous Glands body except on the nipple and
• oil glands parts of the external genitalia
• located all over the body except • Two types:
on the palms of hands and soles
of the feet - eccrine
• usually associated with hair - apocrine
follicles, but some open through
pores in the epidermis of the skin
• secrete an oily substance called A. Eccrine sweat glands
sebum
• Sebum functions in moisturizing (Merocrine)
hair, softening and lubricating the • Found in palms, soles of the feet,
skin,
and forehead as well as over
- preventing water loss from most of the body
evaporation, and in destroying
bacteria

Cont…. Cont….
• Coiled, tubular gland • Regulate by the sympathetic
• Secretory part is coiled in autonomic nervous system
dermis • Role is to cool the body
• Duct opens as a funnel-shaped (thermoregulation)
pore at the skin surface
• Secretes sweat, • Sweat is 99% H2O and
- a hypotonic filtrate of the blood contains NaCl, vitamin
that passes through the C, antibodies, urea,
secretory cells of the sweat uric acid, ammonia,
glands pH4-6
- released by exocytosis

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Cont…. Cont…
B. Apocrine sweat glands
Ceruminous glands
• Found in axillary and anogenital areas
- modified apocrine glands located in the external
• Larger than eccrine glands ear canal below the sebaceous gland
• Ducts empty into hair follicles - open through pores in the epidermis or into the
• Contains same components as sebaceous ducts
true sweat as well as proteins - The combined secretions of the sebaceous glands
and fatty substances making it and the ceruminous glands is called cerumen
viscous
• When its organic molecules are
degraded by bacteria on the skin, it
gives a musky smell (body odor)
• Begin functioning at puberty

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