Classification

Epitheliums can be classified on appearance or on function

Classification based on appearance

- Simple - one layer of cells

- Pseudostratified - looks like more than one layer but is not

- Stratified - more than one layer of cells

Simple epitheliums

Simple squamous epithelium

 Cells are flat with bulging or flat nuclei.  Lines the insides of lung alveoli and certain ducts in the kidney

 Forms serous membranes called mesothelium that line cavities like: pericardial ,  peritoneal,  plural

 Lines blood vessels - known as endothelium

Simple cuboidal epithelium

It appears square in cross section,  Found in: - Ducts of salivary glands,  Follicles of the thyroid gland,  Pigment layer in the eye,  Collecting ducts of the kidney, In the middle ear is ciliated type.

Simple columnar

• Lines the gastrointestinal tract from the stomach to the anal canal,  Some columnar cells have a  secretory function – stomach, peg cells in the oviduct,  Some columnar cells have microvilli on their free border (striated border) – gall bladder, duodenum
• Microvilli increase the surface area for absorption
• Some columnar cells have cilia – oviduct, smaller bronchi
• Cilia transport particles

Pseudostratified

Appears as stratified epithelium but all cells are in contact with the basement membrane.  Has a thick basement membrane. Different cell types make up this epithelium,  Cells that can be found in this type of epithelium are:

• Columnar cells with cilia or microvilli.
• Basal cells that do not reach the surface.
• Goblet cells that secrete mucous.
• Found in the trachea, epididymus, ductus deferens and female urethra

Stratified epithelium

Classified according to the shape of the surface cells

Stratified squamous epithelium

Has a basal layer that varies from cuboidal to columnar cells that divide to form new cells. Two types are found:

Keratinized:  Mostly forms a dry covering, The middle layers consists of cells that are forming- and filling up with keratin. The superficial cells form a tough non living layer of keratin,  Keratin is a type of protein,  The skin is of this type has  thick skin - found on the hand palms and soles of the feet,  thin skin - found on the rest of the body

Non-keratinized:  Top layer of cells are living cells with nuclei  Forms a wet covering,  The middle layers are polyhedral,  The surface layer consists of flat squamous cells

• Is found in:  mouth,  oesophagus,  vagina

Stratified cuboidal epithelium

Found: - in the ducts of sweat glands

Stratified columnar epithelium

Found at the back of the eyelid (conjunctiva)

Transitional epithelium

- Sometimes the surface cells are squamous, sometimes cuboidal and sometimes columnar

- The superficial cells are called umbrella cells because they can open and close like umbrellas, when the epithelium stretch and shrink

- Umbrella cells can have 2 nuclei

- Found in the bladder and ureter

• This is the second cranial nerve (CN II) and is the nerve of sight.

• Articulations

  Classified according to their structure, composition,and movability
  •    Fibrous joints-surfaces of bones almost in direct contact with limited movement
      o    Syndesmosis-two bones united by interosseous ligaments
      o    Sutures-serrated margins of bones united by a thin layer of fibrous tissue
      o    Gomphosis-insertion of a cone-shaped process into a socket

  •    Cartilaginous joints-no joint cavity and contiguous bones united by cartilage
      o    Synchondrosis-ends of two bones approximated by hyaline cartilage
      o    Symphyses-approximating bone surfaces connected by fibrocartilage

  •    Synovial joints-approximating bone surfaces covered with cartilage; may be separated by a disk; attached by ligaments 
      o    Hinge-permits motion in one plane only
      o    Pivot-permits rotary movement in which a ring rotates around a central axis
      o    Saddle-opposing surfaces are convexconcave. allowing great freedom of motion
      o    Ball and socket - capable of movement in an infinite number of axes; rounded head of one bone moves in a cuplike cavity of the approximating bone

  Bursae
  •    Sacs filled with synovial fluid that are present where tendons rub against bone or where skjn rubs across bone
  •    Some bursae communicate with a joint cavity 
  •    Prominent bursae found at the elbow. hip, and knee'

  Movements
  •    Gliding
      o    Simplest kind of motion in a joint
      o    Movement on a joint that does not involve any angular or rotary motions
  •    Flexion-decreases the angle formed by the union of two bones
  •    Extension-increases the angle formed by the union of two bones
  •    Abduction-occurs by moving part of the appendicular skeleton away from the median plane of the body
  •    Adduction-occurs by moving part of the appendicular skeleton toward the median plane of the body
  •    Circumduction
      o    Occurs in ball-and-socket joints
      o    Circumscribes the conic space of one bone by the other bone
  •    Rotation-turning on an axis without being displaced from that axis
   

->The two parietal bones (L. paries, wall) form large parts of the walls of the calvaria.
->On the outside of these smooth convex bones, there are slight elevations near the centre called parietal eminences.
->The middle of the lateral surfaces of the parietal bones is crossed by two curved lines, the superior and inferior temporal lines.
->The superior temporal line indicates an attachment of the temporal fascia; the inferior temporal line marks the superior limit of the temporalis muscle.
->The parietal bones articulate with each other in the median plane at the sagittal suture. The medial plane of the body passes through the sagittal suture.
->The inverted V-shaped suture between the parietal bones and the occipital bones is called the lambdoid suture because of its resemblance to the letter lambda in the Greek alphabet.
->The point where the parietal and occipital bones join is a useful reference point called the lambda. It can be felt as a depression in some people.
->In addition to articulation with each other and the frontal and occipital bones, the parietal bones articulate with the temporal bones and the greater wings of the sphenoid bone.
->In foetal and infant skulls, the bones of the calvaria are separated by dense connective tissue membranes at sutures.
->The large fibrous area where several sutures meet are called fonticuli or fontanelles.
->The softness of these bones and looseness of their connections at these sutures enable the calvaria to undergo changes of shape during birth called molding. Within a day or so after birth, the shape of the infant’s calvaria returns to normal.
->The loose construction of the new-born calvaria also allows the skull to enlarge and undergo remodelling during infancy and childhood.

->Relationships between the various bones are constantly changing during the active growth period.
->The increase in the size of the cranium is greatest during the first 2 years, the period of most rapid postnatal growth of the brain.
->The cranium normally increases in capacity until about 15 or 16 years of age; thereafter the cranium usually increases only slightly in size as its bones thicken for 3 to 4 years.

•     Part of the axial skeleton; strong, flexible rod
      Supports the head
      Gives base to the ribs
      Encloses the spinal cord
      
  o    Vertebrae
      Consists of 34 bones composing the spinal column
  •    Cervical-7 bones
  •    Thoracic-12 bones
  •    Lumbar-5 bones
  •    Sacral- 5 bones.
  •    Coccygeal-4 to 5 bones

      In the adult the vertebrae of the sacral and coccygeal regions are united into two bones, the sacrum and me coccyx
      
  o    Curvatures-from a lateraI view there are four curves, alternately convex and concave ventrally
      Two convex curves are the cervical and lumbar
      Two concave curves are the thoracic and sacral

  o    Vertebra morphology

      Each vertebra differs in size and shape hut has similar components
      Body-central mass of bone
  •    Weight bearing
  •    Fonns anterior part of the vertebra
  •    Encloses the vertebral foramen
      Pedicles of the arch-two thick columns that extend backward from the body to meet with the laminae of the neural arch 

•     Process (7)
  •    One spinous, two transverse, two superior articular, and two inferior articular
  o    Spinous process extends backward from the point of the union of thetwo laminae
  o    Transverse processes project laterally at either side from the junction of the lamina and the pedicle
  o    Articular processes arise near the junction of the pedicle and the lamina- superior processes project upward:inferior processes project downward
  •    Surfaces of the processes are smooth

  o    Inferior articular processes of the vertebra fit into the superior articular processes below
  o    Form true joints, but the contacts established serve to restrict movement

  Distinguishing features

  Cervical region- triangular shape

  •    All have foramina in the transverse process upper six transmit the vertebral artery
  •    Spinous processes are short
      o    C3 to C5 are bifurcated
      o    C7 is long-prominence felt at the back of the neck
  •    Have small bodies (except for C1 vertebra)
  •    C1 vertebra (atlas)
  o    No body
  o    Anterior and posterior arch and two lateral masses
  o    Superiorarticular processes articulate with the condyles of the occipital bone
  •    C2 vertebra (axis)-process on the upper surface of the body (dens) forms a pivot about which the axis rotates

  Thoracic region

  •    Presence of facets for articulation with the ribs (distinguishing feature)
  •    Processes are larger and heavier than those of the cervical region
  •    Spinous process is directed downward at a sharp angle
  •    Circular vertebral foramen

   Lumbar region
   
  •    Large and heavy bodies
  •    Four transverse lines separate the bodies of the vertebrae on the pelvic surface
  •    Triangular shape-fitted between the  halves of the pelvis
  •    Four pairs of dorsal sacral foramina communicate with four pairs of pelvic sacral foramina

  Sacral vertebrae 
  •    Five (sometimes six) vertebrae are fused in the adult to form the sacrum
  •    The sacrum articulates above with L5, laterally with the hip bones, and inferiorly with the coccyx.
  •    It has a roughly triangular appearance with a pelvic and dorsal surface, a lateral mass on each side, and a base and apex.
  •    An anesthetic for the spinal nerves may be injected extradurally through the sacral hiatus (caudal analgesia)
  •    The sacral canal (which contains the dura, cauda equina, and filum terminale) extends from the base to the sacral hiatus. 
  •    The apex of the sacrum may be fused with the coccyx.

  
  Coccygeal vertebrae

  •    Four to five modular pieces fused together
  •    Triangular shape with the base above and the apex below

  F Defects

  •    Lordosis-exaggerated lumbar concavity
  •    Scoliosis-lateral curvature of any region
  •    Kyphosis-exaggerated convexity in the thoracic region

The Arteries of the Face

• The superficial arteries are derived from the external carotid arteries.

The Facial Artery

• This is the chief artery of the face.
• It arises from the external carotid artery and winds its way to the inferior border of the mandible, just anterior to the masseter muscle.
• It hooks around the inferior border of the mandible and grooves the bone. Here the artery is superficial, just beneath the platysma and its pulsation can be felt.

• In its course over the face to the medial angle of the eye, the facial artery crosses the mandible, buccinator muscle, and maxilla.
• It lies deep to the zygomaticus major.

• The facial artery ends by sending branches to the lip and side of the nose.
• The part of the artery that runs along the side of the nose to supply the eyelids is called the angular artery.

The Superficial Temporal Artery

• This artery is the smaller of the two terminal branches of the external carotid artery (the other is the maxillary artery).
• It begins deep to the parotid gland, posterior to the neck of the mandible, and ascends superficial to the posterior end of the zygomatic process of the temporal bone. It then enters the temporal fossa.

• The superficial temporal artery ends in the scalp by dividing into the frontal and parietal branches.

• Pulsation of this artery can be felt by compressing the root of the zygomatic process of the temporal bone.

The Transverse Facial Artery

• This small artery arises from the superficial temporal artery before it emerges from the parotid gland.
• It crosses the face superficial to the masseter muscle, about a fingerbreadth inferior to the zygomatic arch.
• It divides into numerous branches that supply the parotid gland and duct, the masseter muscle, and the skin of the face.

• It anastomoses with branches of the facial artery.