BIO 1110

1

Tissues: A group of similar cells, having a similar origin, and functioning together to carry out specialized activities.

Tissues can be solid, semi-solid or liquid. From conception until approximately day 14,

all cells look and function the same (undifferentiated=stem cells).

Around day 15 post conception, cells start to differentiate or take on new characteristics. This is the start of tissue formation.

2

Histology is the study of tissues.There are 4 main types of tissues in the

human body: Epithelial Connective Muscular Nervous

3

Tightly packed cells arranged in continuous single or multi-layered sheets.

Characteristics: Avascular- without blood vessels.

Epithelium gets nutrients from the adjacent connective tissue.

Bottom surface of epithelium is attached to the basement membrane (fibers that act like glue)

Has a nerve supply.

4

This type of tissue is found on the outer covering of the skin and some internal organs as well as lining body cavities and some internal hollow organs.

There are 9 different types of lining/covering epithelium. Epithelial tissue is classified based on the

number of cell layers present and the shape of the cells of the tissue.

Simple-- Single layer of tightly

packed cells

Stratified-- 2 or more layers of

tightly packed cells

7

Pseudostratified Looks like many layers

because not all cells reach the surface and the nuclei lie at different levels

8

SquamousThin, flat and irregularly shaped

Cuboidal Square/cube shaped

Columnar taller than wide

Transitional change shape due to stretching or movement of

body parts

9

A single layer of tightly packed thin, flat, irregularly shaped cells

Location: Lines the blood vessels Forms the peritoneum, pericardium and

pleural linings Found in the air sacs of lungs (alveoli)

Function: Allows for easy diffusion of gases and blood

components

Simple Squamous – Top View – found in the walls of capillaries and alveoli of lungs

A single layer of tightly packed cube shaped cells.

Location: Lines kidney tubules, ducts of glands, and

secreting parts of glands

Function: Secretion (force materials out of the cells)

and absorption (pull materials into the cells)

Simple Cuboidal Epithelial Tissue – this is of ducts of the kidney

A single layer of tightly packed rectangular cells Can be non-ciliated or ciliated (tiny hairs) Non-ciliated have microvilli (finger-like

projections) on the free surface of the cellsNon-ciliated Location:

Lines the gastrointestinal tract (from stomach to anus)Non-ciliated Function:

Secretion and absorption Microvilli increase surface area 200-300 times for

absorption

04/20/23 18

Ciliated Location: Lines tubes of the respiratory tract,

fallopian tubes, and ventricles of the brainCiliated Function:

The cilia beat in unison to move substances outside the cell like mucus and egg cells.

Simple Columnar Non-Ciliated Epithelial Tissue - This is a cross section through the small intestine – for absorption – microvilli on surface of cells

23

A single layer of tightly packed columnar cells that appear to be multi-layered

Location: Ciliated- Lines respiratory tract Non-ciliated- Male urethra

Function: Ciliated- moves materials across the apical

surface of a tissue. Non-ciliated- Absorb and protect

Multiple layers of tightly packed squamous epithelial cells.

Location: Areas that are subject to much “wear

and tear”.▪ Upper layers are designed to be shed and

replaced.

Function: Protection

Two layers of cube shaped epithelial cells

RareLocation:

Lining the ducts of glands found in the esophagus

Function: Moderate protection from the stomach

acid that refluxes

Multiple layers of columnar epithelial cells Rare Only the layer closest to the lumen

(opening in a duct) is columnar in shape. The outer layers are somewhat squashed.

Location: Lining the ducts of glands lining the esophagus

Function: Moderate protection from stomach acid that

refluxes

Epithelial tissue that has a variable shape

Can stretch and relax multiple times without being damaged

Location: Lines the urinary bladderFunction: Protection