fibrils are arranged in delicate bundles, in the meshes
4
50 TISSUES
of which are the functionating cells of the glands.
The cells of this variety are mostly stellate.
5. The Mixed or Areolar Tissue. This contains
both white and elastic tissue. It shows a net-work
of fine white fibrils, with elastic fibrils scattered
throughout, and they are usually branched. The
cellular elements scattered among these fibrils are
stellate, plasma, and wandering forms. Areolar tissue
is very fine, delicate, loose in texture, and binds the
skin to the underlying fasciae, and lies between muscles.
6. Adipose or Fatty Tissue. This is white fibrous
tissue, in which fat cells are deposited. In the living
body it is liquid at the temperature of the body. It
can only be seen in the tissues under the microscope
after special preparation. It is essential to know, how-
ever, that it is found and can be seen as a yellowish
layer beneath the skin (postmortem), surrounding
organs, etc., which act as a covering or protection to
them; it has a wide distribution and is never found in
the ear, eyelid, or genitalia (male), and is always found
back of the eye-ball and in the kidney, no matter how
poorly nourished an individual may be, even to the
extent of starvation.
7. Lymphoid Tissue. This is made up of a net-work
of reticulum, holding among its fibers the white blood-
cells or leukocytes. The cells seen are mostly small
lymphocytes, and some large lymphocytes and poly-
nuclear cells. (See blood, page 221.) There are three
varieties of lymphoid tissue: (a) diffuse; (b) solitary
follicles; (c) Peyer's patches; and lymph nodes.
(a) The diffuse variety is found in the tunica propria
of the mucous membrane of the alimentary and respir-
atory tracts, the medulla of the thymus body, and
the greater portion of the tonsil and spleen. (6)
Solitary follicles are found in the alimentary and
respiratory tracts, spleen, and tonsils. (c) Peyer's
patches consist of a collection of solitary follicles clearly
outlined from the surrounding tissue. They are found
CONNECTIVE TISSUES 51
in the wall of the ileum (the terminal portion of small
intestines which opens into the cecum) . Lymph nodes
(glands). (See Lymphatic System.)
8. Cartilage. Cartilage is not as compact or strong
as bone. It is more yielding; thus it will be found in
different parts of the body when this firm yet pliable
property is essential to the function of an organ. We
see it in the cartilages of the larynx, where one may
readily understand how its structure must be more or
less elastic owing to the constant action of the muscles
upon the cartilages and their change in relationship
during talking, singing, etc., and its value can be
appreciated when placed between bones, as a shock
absorber; demonstrated by the intervertebral disks
between each vertebra.
In studying the structures of cartilage it is con-
sidered under perichondrium, cells, and intercellular
substance. The perichondrium is a fibrous sheath
which surrounds cartilage and corresponds to the
periosteum of bone. It is divided into an outer fibrous
layer containing few cells, and an inner portion or
chondrogenetic layer, consisting of flattened and elon-
gated or spindle-shaped cells. These are the chondro-
blasts or cartilage cells. The latter cells are seen just
beneath the perichondrium, where they appear as flat
cells, then as the centre of the cartilage is reached
they become more oval or even round. Each cell is
rich in protoplasm and contains one or more vacuoles.
The cell is surrounded by a capsule, and a small space
intervenes, between the cell and the capsule called
a lacuna. The intercellular substance consists of a
homogeneous mass in the hyaline cartilage, and of
white fibrous and yellow elastic fibers, in the white
fibrocartilage and yellow fibrocartilage respectively.
There are three varieties of cartilage: Hyaline,
white fibrocartilage, and yellow fibro or elastic.
The hyaline cartilage is pearl blue in color, is elastic,
and cuts with a knife. It is found in the body covering
52 TISSUES
articular surfaces of bones, which line joint-cavities;
in costal cartilages as found between the ribs and
breast bone or sternum; in cartilages surrounding the
trachea (windpipe); and in most of the laryngeal
cartilages. It may ossify in old age.
The white fibrocartilage is not very plentiful and acts
as a structure to deepen joint-cavities, as interarticular
fibrocartilages and intervertebral disks.
Yellow fibrocartilage is found wherever elasticity is
required, as in the epiglottis, Eustachian tube, ear, and
smaller laryngeal cartilages. It never ossifies.
Cartilages are very poorly nourished, as they do not
contain many bloodvessels, except in the perichon-
drium; and except when the cartilage is developing.
No lymph channels are present.
NOTE. Muscle, osseous, and nerve tissues are de-
scribed under the chapters on Muscles, Bones, and
Nerves respectively.
QUESTIONS
1. What do you understand by the term maturation? Fertiliza-
tion?
2. What three layers of cells are developed from the ovum after
maturation and fertilization are completed?
3. What are the tissues of the body divided into?
4. Name the functions of epithelial tissue.
5. In what cavities of the body are epithelial cells found?
6. Give the classification of epithelial cells.
7. How do ciliated cells differ from other cells?
8. What is characteristic of stratified cells?
9. In which direction do the motion possessed by ciliated cells
point?
10. What layers of tissues enter into the formation of a normal
mucous membrane?
11. Which layer contains bloodvessels, lymphatic spaces, nerves,
glands, and lymphoid tissue in certain organs?
12. Which layer contains involuntary non-striated muscle tissue?
13. Give the subdivisions of glands.
14. What are the three varieties of secretions from glands?
15. How do serous membranes differ from mucous membranes?
16. What name is given to the type of cells covering the serous
membranes?
17. Where are serous membranes found throughout the body?
QUESTIONS 53
18. Wht is the function of connective tissue?
19. Give the classification of connective tissues?
20. Where is yellow elastic tissue found?
21. What tissue enters into the frame-work of glands and gland-
like organs?
22. Is adipose tissue liquid at the temperature of the body?
23. What structures of the body are always free from fat?
24. Name the three varieties of lymphoid tissue.
25. Is cartilage as strong as bone?
26. What is the essential property of cartilage as found in the
body?
27. Name the varieties of cartilage?
28. Describe hyaline cartilage and where is it found? Does it
ossify?
29. Where do you find white fibro cartilage? Yellow fibrocartilage?
30. What is the function of mixed or areolar tissue?
CHAPTER V
OSTEOLOGY THE DESCRIPTION OF BONES
AND BONE TISSUE
THE bones entering into the supportive structure
of the body are held in close relation with each other
by means of ligaments and muscles. Thus the skeleton
consists of a strong, firm frame-work, possessing all
manner of movements due to the action of the attached
muscles and the leverage of the bones, allowed by the
ligaments holding the bones in relation with one
another. The body skeleton consists of two hundred
and six bones, as follows:
[Vertebral column 26
Axial 1 Skull 22
skeleton ] Hyoid bone 1
[Ribs and sternum 25
74
Appendicular f Upper limb 64
skeleton \Lower limb 62
126
Auditory ossicles (bones of ear) 6
Total 206
The patellae, two in number, are included in this
list, but not the sesamoid bones. The latter are small
bones (shaped like sesame seed) found embedded in
tendons covering the knee, hand, and foot.
Classes of Bones. Bones are divisible into four
classes: long, short, flat, and irregular.
Long Bones. These are found in the limbs, they
support the weight of the trunk and form a system of
CLASSES OF BONES 55
levers which permit the power of locomotion and
prehension. Long bones possess a shaft and an upper
and lower extremity. The shaft or the diaphysis is
cylindrical, containing in the centre a hollow cavity,
the medullary canal, in which during life is the bone-
marrow. Surrounding this is dense compact tissue of
considerable thickness, but not so thick near the
extremities. The extremities or epiphyses are usually
expanded to enable one bone to articulate with another
and to afford attachment of muscles. They are usually
developed from separate centres of ossification called
epiphyses. Examples of long bones are the femur or
thigh bone, the humerus or bone of the arm, the clavicle
or collar bone, the radius and ulna (bones of the fore-
arm), the tibia and fibula (bones of the leg), the meta-
carpal, metatarsal, and phalanges (the small bones of
the hand and foot) respectively.
Short Bones. These are found in that portion of the
body where strength and compactness are required
and the motion of the part is limited, as the bones of
the carpus (wrist) and tarsus (instep). These bones
consist of cancellous tissue covered by compact bone.
They are held firmly together by ligaments. Some
include the patellae and sesamoid bones under this
variety.
Flat Bones. These are found wherever protection
is required, or a broad surface for the attachment
of muscles is essential, as the bones of the skull and
the scapulae (shoulder-blade) . Flat bones are composed
of two thin layers of compact tissue, between which is
a variable amount of cancellous tissue. In the bones
of the skull these layers of compact tissue are termed
the tables of the skull ; the innermost is thin and called
the vitreous table. The cancellous tissue between the
layers is called the diploe.
The flat bones are the occipital, parietal, frontal, nasal,
lacrymal, vomer, scapula, sternum, ribs, and some authors
include the patella.
56 OSTEOLOGY
Irregular Bones. These are of varying shapes which
cannot be classified under any of the preceding groups.
They consist of a layer of compact tissue externally
enclosing cancellous tissue.
The irregular bones are: the vertebrae, sacrum, coccyx,
temporal, sphenoid, ethmoid, malar, maxilla, mandible,
palate, turbinates, and hyoid.
Surfaces of Bones. The examination of a bone
will show numerous depressions and elevations upon
its surface, which for purposes of study have been
classified into the following eminences and depressions :
(1) articular; (2) non-articular. Examples as follows:
Articular.
TT;,, =, /Head of femur.
Eminences Qf humerug>
-j-v . fGlenoid cavity of scapula.
n \Acetabulum of os innominatum.
Non-articular.-
Eminences
Depressions
Tuberosity is a broad, rough, uneven elevation.
Tubercle is a small, rough prominence.
Spine is a sharp, slender, pointed eminence.
A ridge, line, or crest are narrow, rough elevations
along the surface.
Notches.
Fossae.
Grooves.
Furrows.
Fissures.
All are of variable form.
The articular eminences and depressions are the
extremities and cavities of bones which enter into the
formation of joints respectively. The non-articular
eminences are to increase the surface of the bone for
the attachment of muscles and ligaments; the depres-
sions usually receive, hold, or keep in position tendons
or muscles, and transmit bloodvessels and nerves.
COMPOSITION AND STRUCTURE OF BONE 57
Composition and Structure of Bone. Bone in the
fresh state is pale pink in color, when dried it is grayish
white. The constituents of dried bone are 31 per cent,
organic matter and 69 per cent, inorganic matter.
The former is represented by bloodvessels and con-
nective tissue, and proteins, such as collagen, ossein,
elastin; the latter by mineral salts, e. g., tricalcium and
magnesium phosphate, calcium carbonate, and some
soluble salts. These ingredients may vary with the
age of the individual. Thus in the child there is an
increase in the organic matter over the mineral con-
stituents, while the mineral salts predominate in bones
of the adult. This absence of salts in the bones of
children accounts for the elasticity of the bones,
and when fractured they bend rather than break
after an injury. This can be seen when a fractured
limb, exposed to the a>rays, will appear as a twig bent,
but no distinct break is seen (this is termed a green-
stick fracture). On the other hand in extremely old
persons there is a tendency to fracture of the bones,
due to the increase of mineral salts over the organic
constituents, rendering them brittle, and unable to
withstand the slightest strain without fracture. Rick-
ets is another example of this decrease in lime salts
in the bones. It is a disease occurring in children
mostly, characterized by a bending of the long bones,
and deformity of the limbs, as a result of insufficient
and improper nourishment. Bone belongs to the
connective-tissue group, and is derived from the
mesoderm layer of the'tripoblast, the primitive vesicle
of the embryo.
Periosteum. All bones are surrounded by a fibrous
sheath, called the periosteum, enclosing the bone sub-
stance; the latter is composed of cells and intercellular
substance. The periosteum consists of two layers:
an outer fibrous, supporting bloodvessels, an inner
or genetic layer, rich in cells and blood capillaries.
The cells in the latter become the future osteoblasts
58 OSTEOLOGY
that develop the osseous tissue by a process of cell
secretion. The genetic layer gives off bundles of fibers
which pierce the layers of bone at right angles and
bind them together. These are called Sharpey's fibers.
Bone is classified as to its composition into cancellous
or spongy, compact or solid.
Cancellous or Spongy Bone. This consists of spicules
forming a net-work similar to a sponge. These spicules
have a fibular structure, and between them are small
spaces called lacuna? (little lakes), which are filled
in the living state with osteoblasts. The cancellous
bone is found in the head of long bones, the centre
of flat bones, and around the medullary cavity. In
the centre of all long bones is a hollow cavity called
the medulla; it contains marrow. This medullary
cavity is lined with a fibrous layer of tissue called the
endosteum, which covers the net-work of spongy bone
surrounding the medullary canal.
Compact or Solid Bone. This is the stronger of the
two varieties and forms the outer surface of the
long bones. It is arranged in layers called lamella?,
and can only be studied in section after preparation;
and when observed under the microscope it will present
a series of lamellae arranged around a central opening,
called the Haversian canal. These carry bloodvessels
in a longitudinal direction throughout the bone,
and communicate with each other. Between the
Haversian canals are lacunae lined with osteoblasts
they communicate with each other and the Haversian
canals by means of small canals called canaliculi.
Just beneath the periosteum the lamellae of bone are
derived from it. These layers have between them
lacunse with canaliculi connecting each other. The
most external lamella? present depressions termed
Howship's fovese or lacunas; these are filled with large
bone-destroying cells called osteoclasts. Haversian
canals are absent in the external lamellae beneath the
periosteum, but large canals are present, containing
blood from the periosteum Volkmann's canals.
BONES OF THE HEAD 59
The Haversian canals are occupied by bloodvessels,
nerves, and lymphatics, except in the region of the
heads of long bones; owing to their absence this por-
tion of the bone is better enabled to withstand the
pressure imposed upon it. The above arrangement
of canals is termed the Haversian System.
The medullary cavity is a large space within the
centre of the long bones. It is lined by a fibrous layer,
the endosteum, and contains the nutrient marrow.
Marrow is of two varieties, red and yellow. The
former color is seen in healthy, young individuals, the
latter occurs in those beyond the prime of life. The
presence of a great amount of fat causes the latter to
assume its yellow color. The cellular elements are few
or are wanting. In disease it may become red. It is
derived from the endosteum between the compact bone
and the medullary cavity, and consists of a delicate
frame-work of reticulum holding a compact capillary
plexus and cells. These cells are classified as: Marrow
cells or myelocytes, nucleated red blood cells or erythro-
blasts, white blood cells or leukocytes, myeloplaxes. (For
a better knowledge of these cells the reader is referred
to the standard works on histology or hematology.)
The function of red marrow is to produce erythro-
cytes, granular leukocytes, and to store fat. Bones
are nourished by an artery which enters the nutrient
foramen, seen on the surface of bones, and by branch-
ing into smaller vessels, called capillaries, pass into
the Haversian canals;, other vessels enter Volkmann's
canals to nourish the most external lamellae beneath
the periosteum.
BONES OF THE HEAD
The skull is divided into two parts: the cranium
and face; the former lodges and protects the brain
and its membranes, bloodvessels, and nerves; the
60 OSTEOLOGY
bones of the face partially surround the orbital cavity
and form the walls of the nasal and oral cavities.
The cranium has eight bones.
(a) Unpaired: ^6) Paired:
Occipital. Temporal.
Sphenoid. Parietal.
Ethmoid.
Frontal.
The face has fourteen bones:
(a) Unpaired: (6) Paired:
Vomer. Nasals.
Mandible. Maxillae.
Lacrymals.
Malars.
Palates.
Turbinates.
The Bones of the Cranium. The Occipital Bone.
This is situated in the back part and base of the skull,
is flattened, lozenge-shaped, bent on itself, presenting
an internal or cerebral surface, which is concave, and
an external or posterior surface, which is convex; four
borders and four angles. Below and in front the
bone shows a large oval opening, called the foramen
magnum, for the passage of the spinal cord and mem-
branes, spinal accessory nerves, and two vertebral
arteries. On either side of the anterior boundaries
of the foramen magnum are two condyles which
articulate with the atlas (first cervical vertebra).
Anteriorly a rough process of bone (the basilar) artic-
ulates with the body of the sphenoid and temporal,
and the posterior border of the occipital bone articu-
lates with the parietal Bones on either side.
The Parietal Bones. These are paired one on either
side, together forming the median portion of the roof
BONES OF THE HEAD
61
and sides' of the skull. Each is roughly quadrilateral,
and presents two surfaces external and internal, four
borders and four angles. This bone articulates, at
the anterior border, with the frontal bone; posterior
border, with the occipital bone; internal border, with
opposite bone; inferior border, great wing of sphenoid;
squamous portion of temporal, and the mastoid por-
tion of the temporal.
FIG. 26
UGULAR PROCESS
ARROW IN ANTERIOR
CONDYLAR FORAMEN
The occipital bone, viewed from below. (Spalteholz.)
The Frontal Bone. This forms the forehead, and
also enters into the roofs of the orbital and nasal
cavities. Its anterior surface is convex and the con-
vexity is greatest on either side, where the rounded
frontal eminences are to be seen, separated by a slight
depression below from the superciliary ridges. The
latter ridges are just above the orbits and afford pro-
tection to them from injury. In the middle line be-
tween the two ridges is a smooth surface the glabella.
62
OSTEOLOGY
The orbital arch ends in extremities called the internal
and external angular processes. The frontal sinuses
(hollow spaces) which communicate with the nasal
cavities contain air, and are lodged in the frontal
bone just above the orbital arches. The frontal bone
articulates with twelve bones the parietals, the
sphenoid, the malars, the nasals, the superior maxillae,
lacrymals, and ethmoid.
FIG. 27
Left parietal bone, external surface. (After Gray.)
The Temporal Bones. These are paired, assist in
forming the sides and base of the skull, and contain
the organ of hearing. They present three parts
squamous, petromastoid, and tympanic.
BONES OF THE HEAD
63
THE SQUAMOUS PORTION. This is scale-like in form
and very thin. Its external surface is convex, smooth,
and affords attachment to the temporal muscle and
FIG. 28
^Internal External
igular process. anptt j ar proce88t
Nasal spine,
Frontal bone. Outer surface.
(Gray.)
bounds part of the temporal fossa. Proceeding for-
ward from the lower part of this portion of the bone
is a long arched process of bone, the zygoma or zygo-
matic process.
64
OSTEOLOGY
THE PETROMASTOID PORTION. This consists of the
mastoid portion, the thick, conical process of bone
behind the external opening of the ear, and a pyram-
idal portion called the petrous portion, forms part of
the floor of the skull. The mastoid portion contains on
FIG. 29
Glenoid fossa.
% Mastoid
foramen..
DIGASTRIC.
Left temporal bone: outer surface. (Gray.)
section a number of cellular spaces communicating
with one another, called the mastoid cells. The
mastoid cells open into the middle ear, and contain
air. They are lined with a prolongation of mucous
membrane from the tympanum, which extends into
them through an opening, by which they communicate
BONES OF THE HEAD 65
with the, cavity of the tympanum. The petrous por-
tion is a pyramidal process of bone wedged in at the
base of the skull, between the sphenoid and occipital
bones. It has a foramen internal auditory for the
passage of the facial and auditory nerves.
THE TYMPANIC PORTION. This is placed in front
of the anterior surface of the petrous portion. It
bounds the external auditory meatus in front, below
and behind, and lodges the tympanic membrane (ear-
drum) .
The glenoid fossa is a depression formed by the squa-
mous part of the temporal and behind by the tym-
panic portion. It is covered with cartilage (squamous
portion) and articulates with the condyle of the
mandible.
The Sphenoid Bone. This wedge-like bone is placed
across the base of the skull near its middle, and binds
the other cranial bones together. It assists to form
the cavities at the base of the cranium, orbits, and nasal
fossa, and has foramina and fissures for the passage
of six pairs of cranial nerves. It consists of a solid
body of bone, with a thin pair of lesser and greater
wings. It articulates with twelve bones, all those of
the cranium and five of the face; posteriorly, with the
occipital and temporals; anteriorly, with the ethmoid,
palatals, frontal, and malars; laterally, with the tem-
porals, frontal, and parietals ; inferiorly, with the vomer
and palatals. The upper surface of the body of the
sphenoid supports the pituitary body, and the circular
and cavernous sinuses, the latter enclosing the internal
carotid artery.
The Ethmoid Bone (sieve-like). This projects down
between the orbital plates of the frontal, and enters
into the formation of the floor of the anterior cranial
fossa, the orbital, and nasal cavities. It is a very
small, frail bone. Its upper surface lodges the olfactory
bulb and portions of the olfactory tract. The fila-
ments of the olfactory nerve (sense of smell) pass
5
66
OSTEOLOGY
through foramina in the cribriform plate to be dis-
tributed to the mucous membrane of the nasal cavities.
The anterior, middle, and posterior ethmoidal cells are
lodged in this bone; they communicate with the nasal
cavities. It possesses a perpendicular plate, which
forms a portion of the nasal septum between the two
nasal cavities.
Bones of the Face. The Two Nasal Bones. These
form the bridge of the nose. They are very small
but strong considering their size.
Perpendic*
plate of etlt
moid.
Space for
triangular
cartilage
of septum.
Vomer.
FIG. 30
Frontal sinuses.
Sphenoidal sinuses.
Palate process
Lit. ptcri/(i<>i<i
plate.
Vomer in situ.
The Vomer. This is a thin flat bone which joins
with the perpendicular plate of the ethmoid bone, and
BONES OF THE HEAD 67
septal cartilage to complete the septum between the
nasal cavities. It articulates with the sphenoid,
ethmoid, both palates, superior maxillae, and with the
septal cartilage of the nose.
FIG. 31
Nasal bone.
Lacrimal bone.
icx
Tfe; Orbital surface.
Infra-orbital
groove.
ifra-orbital
foramen.
nasal spine.
Alveolar