Animal Tissues
By
Fayez A. Elmabhouh
Department of
Biology

Introduction
 Histology = study of tissues
 Tissue = group of cells with similar structure and
function
 They are classified according to the shape of the cell,
size, intracellular matrix.
 Four types of human tissues:
 Epithelial tissue
 Connective tissue
 Muscular tissue
 Nervous tissue
The organ can may consists of one (heart) or
combination of these tissues (stomach, skeleton, skin)

Four Tissue Types:
1 2 3
4

Epithelial Tissues
Characterized by:
 Their closely connected cells.
 Having very little intracellular substance.
 Resting on a basement membrane.
 Arise from the three germ layers.
 No blood vessels enter between its cell but
nerves do
 Covers body surfaces and forms glands.

Basement membrane

Embryonic Tissues – all adult tissues are
derived from one of three embryonic
tissues
gut
Ectoderm =
“outside skin”
Endoderm =
“inside skin”
Mesoderm =
“middle skin”
Cross section
through embryo
Animal embryo

Classification of Epithelium
1. Covering epithelia.
2. Glandular epithelia.

Covering epithelia
 The primary function of this type of epithelia
is protection.
 Covering epithelia classified according to the
arrangement of the cell into simple epithelia
and stratified epithelia.

Simple epithelia
 These tissues divided into four types
according to the shape of cell and location of
nucleus.
 Consists of a single layer of cells that
are in contact with the basement
membrane.

1. Simple Squamous Epithelium:
 The cells are flat with
smooth edges.
 They appear spindle-
shaped in cross section
 Each cell containing a
nucleus in the widest
area.
 Found in the lining blood
vessels, covering serosa

Blood vessel

Serosa

Simple Squamous Epithelium
Simple Squamous Epithelium Bowman’s capsule

2. Simple Cuboidal Epithelium
 The cells in this
epithelium are
square-shaped in
cross section.
 Have central and
round nucleus.
 Lining the kidney
tubules and Follicles
of thyroid gland

Follicles of thyroid gland

Simple Cuboidal Epithelium
cells
single layer of cube shaped cells; large nuclei

3. Simple Columnar Epithelium
 Built of long pillar-
shaped cells.
 Containing an oval
nucleus.
a. Ciliated: Bronchioles
b. Non Ciliated:
lining the ileum

4. Pseudo-stratified Epithelium
 Single layer of cells which rest on a
basement membrane but do not all reach to
the free surface of the epithelium.
 Their nuclei found at different levels giving
the a false stratified appearance.
 Cells that reach the surface carry cilia at their
free ends.
 Lining the trachea.

 Keratinized: the epithelium is covered with
keratin layer which is formed by the dead
squamous cells (horny layer) Skin.
 Non- keratinized: esophagus

Non- keratinized

Keratinized: Skin
1. Epidermis (Stratified Squamous Epithelium)
2. Dermis

Transitional- stratified
 Found in the urinary tract (urinary bladder)
 Rest on a non clear and non wavy basement
membrane.
 Its superficial cells are cuboidal in shape, and
may contain 2 nuclei.
 The basal cell layer is formed of high
cuboidal cell.
 The intermediate layer are polyhydral cells.
 Empty
 Full, the cell change into to squamous cell

Glandular Epithelium
 The cells are specialized in secretion and
thus form glands.
 Formed from collections of Epithelial cell
 Glands with ducts are termed exocrine
 Glands without ducts are termed endocrine

Exocrine Glands
1. Unicellular: formed of single cell
present in the respiratory tract and
intestinal tract

Multicellular gland
 Made of many cells and each consist of a
secretary portion and duct.
 They are either tubular, alveolar in form and
may be simple or compound.

Simple tubular glands
 In the digestive glands, stomach, Large
intestine

Simple alveolar gland
 Form of a flask with a round secretary portion
and a narrow tubular duct.
 Mucous and sebaceous gland skin

Compound tubular glands

Compound alveolar gland
 Parotid gland