ANATOMY & PHYSIOLOGY LABORATORY

CELLS & TISSUES

The human body contains over a trillion cells. These cells form the organs of the human body and are
responsible for organ function. Cells take in nutrients delivered to them by the blood and use these nutrients to
make carbohydrates, proteins, lipids, and nucleic acids. Cells use these macromolecules to make cellular and
extracellular structures, repair themselves, and to perform the tasks required for organ function.

Cell Structure
Cells are the smallest structural and functional units of living organisms. They are enclosed by a plasma
membrane which controls the movement of substances into and out of the cell. The interior of the cell is filled
with cytoplasm that contains cytosol (a viscous fluid) and organelles (little organs). Like an automobile, a cell has
different parts or organelles that perform different functions. A “generalized” animal cell is shown in Figure 3.1,
and functions of cellular organelles are described in Table 3.1.

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LAB ACTIVITY 1

1. Study the cell model in Figure 3.1 and identify the different organelles and structures.
2. Describe the function of each organelle as you point it.
3. Interactive Access. Log in to https://bit.ly/30GGPlC to access your Mastering A&P.
4. Click the Study Area  Study by Chapter  Cells and Tissues  eText.
5. Study the general functions of each cell structure and organelle

THINK TANK!
Which cell structures from Figure 3.1 are not found in most human cells?

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Cell Specialization
The human body contains over 200 different types of cells with different functions. These differences in
function are reflected in cell structure. Cells of the human body differ from the generalized animal cell in shape,
size, or number and type of organelles present. In the next activity you will observe cells of skeletal muscle,
pseudostratified ciliated columnar epithelium, non-ciliated simple columnar epithelium with microvilli, motor
neurons, sperm, and blood.
 Skeletal muscle cells are long, cylindrical cells that contain specialized proteins (contractile proteins)
that enable them to contract (shorten in length) to move bones. The contractile proteins are organized
into repeating units that can be observed in the light microscope as striations.
 Pseudostratified ciliated columnar epithelial cells have cilia that move substances like mucus along
the surface of the cells. Mucus is produced by specialized cells called goblet cells.
 Non-ciliated simple columnar epithelium with microvilli. Microvilli increase the surface area of the
plasma membrane which provides a larger area for absorption of nutrients along the gastrointestinal tract
or secretion of product from glands.
 Motor neurons are nervous tissue cells with many processes (cell extensions) that receive information
from other neurons and send electrical signals to muscle cells causing them to contract.
 Sperm cells (sperm) are small, oval cells with a flagellum that propels them through the female
reproductive tract.
 Red blood cells do not have a nucleus (anucleate) but contain large amounts of hemoglobin, a red
pigment that binds oxygen.
 White blood cells have nuclei with different shapes and defend the body from pathogens and cancerous
cells.

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LAB ACTIVITY 2

1. Compare some of the different kinds of cells from the photomicrograph above and describe their
visible similarities and differences.
2. Describe each cell’s shape and list the cell structures that can be observed.

Cell Division and Cytokinesis

The cell cycle is a series of events that most cells complete during their life span. It includes two stages—
interphase, the longer period when the cell grows and carries out its usual activities, and cell division, when
the cell reproduces itself by dividing. In an interphase cell about to divide, the genetic material (DNA) is replicated.
Once this important event has occurred, cell division occurs. Cell division in all cells other than bacteria consists
of a series of events collectively called mitosis and cytokinesis.
Mitosis is nuclear division; cytokinesis is the division of the cytoplasm, which begins after mitosis is
nearly complete. Although mitosis is usually accompanied by cytokinesis sometimes division of the cytoplasm
does not occur, and binucleate (or multinucleate) cells are formed. This is relatively common in the human liver
and during embryonic development of skeletal muscle cells. The products of mitosis are two daughter nuclei
that are genetically identical to the mother nucleus. The function of mitotic cell division in the body is to increase
the number of cells for growth and repair. The stages of mitosis illustrated in Figure 3.3 below include the
following events:
 Prophase (Figure 3.3b and c): As cell division begins, the chromatin threads coil and shorten to form
densely staining, short, bar- like chromosomes. By the middle of prophase, the chromosomes are
obviously double-stranded structures (each strand is a chromatid) connected by a button-like body
called a centromere. The centrioles separate from one another and direct the assembly of a system of
microtubules called the mitotic spindle between them. The spindle acts as a scaffolding to which the
chromosomes attach and are moved along during later mitotic stages. Meanwhile, the nuclear envelope
and the nucleolus break down and disappear.
 Metaphase (Figure 3.3d): In this brief stage, the chromosomes line up along the central plane, or
metaphase plate.
 Anaphase (Figure 3.3e): During anaphase, the centromeres split, and the chromatids (now called
chromosomes again) separate from one another and then move slowly toward opposite ends of the cell
with their “arms” dangling behind them. Anaphase is complete when pole ward movement ceases.
 Telophase (Figure 3.3f): Events of prophase are reversed. The chromosomes uncoil and resume the
chromatin form, the spindle breaks down and disappears, a nuclear envelope forms around each
chromatin mass, and nucleoli appear in the daughter nuclei.
 Cytokinesis typically begins in late anaphase and continues through telophase (Figure 3.3f) and
provides a good clue for where to look for the mitotic structures visible in telophase. In animal cells, a
cleavage furrow begins to form approximately over the equator of the spindle and eventually pinches the
original cytoplasmic mass into two parts. Once formed, the daughter cells grow and carry out the normal
spectrum of metabolic processes until it is their turn to divide.

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LAB ACTIVITY 3

1. Observe the photomicrograph of mitosis and interphase above. Note the changes in each phase.
2. Interactive Access. Access your Mastering A&P.
3. Click the Study Area  Practice Anatomy Lab (PAL)  Histology  Cytology and review the
different stages of mitosis with labels.
4. Reinforce you understanding by accessing PAL 3.1 Flashcards.

THINK TANK!
List the cell structures involved in mitosis.

CLASSIFICATION OF TISSUES
In multicellular organisms such as humans various groups of cells become specialized for specific
functions. Some cells are responsible for movement, others for protection and still others for transferring food
and oxygen throughout the body. None of these cells could survive independently from the others. Each has
become specialized not only in function but in shape and internal makeup to perform a relatively few functions.
Groups of cells with similar morphology and function are called tissues. Tissue cells are usually
embedded in a non-cellular matrix. The proportion of cells to matrix varies between tissue types. The matrix of
many tissues also contains one or more kinds of protein fibers such as collagen, elastin and reticular fibers.
All mammalian organs and organ systems are composed of just 4 basic or primary tissue types: Epithelial,
Connective, Muscular, and Nervous Tissues. Each of these four primary tissue types can be further subdivided
into several more specific tissue types.
Epithelial tissues line body surfaces and the lumen of all tubes and ducts within the body; including the
digestive system, lungs, kidneys, exocrine glands, etc. Epithelial cells function in protection, filtration, secretion
and absorption. They are packed tightly together with little or no intercellular matrix. Epithelium generally lacks
a direct blood supply and is bound to underlying tissue layers by the basement membrane.
Connective tissue morphology is less well defined than the other 3 tissue types. Non-cellular matrix
material often accounts for a major portion of the space occupied by connective tissues. Tissue cells are
scattered throughout the usually highly vascularized matrix. The matrix itself consists of an amorphous jelly-like
collection of mucopolysaccharides which sometimes contain fibers of collagen or elastin. Connective tissue
provides support in the form of cartilage and bone, stores fats in the form of adipose tissue, and transports
oxygen and metabolic products as blood and lymph.
Muscle tissue is composed of elongated spindle shaped cells that can be up to a foot long arranged in
layers or bundles. Each muscle cells (=muscle fiber) is bounded by a cell membrane called a sarcolemma. The
cytoplasm inside is referred to as the sarcoplasm. Contractile threadlike organelles called myofibrils fill the interior
of the cells.
Nervous tissue is made up of highly specialized cells called neurons whose primary job is to conduct
impulses throughout the body for coordination and control of body activities. Another type of nervous tissue is
neuroglia which supports, protects, insulates and nourishes the neurons.

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LAB ACTIVITY 4

1. Interactive Access. Access your Mastering A&P.

2. Click the Study Area  Study by Chapter  Cells and Tissues  eText.
3. Review the different types of primary tissues, their function and organs where they are located.

THINK TANK!
 Define Histology.
 Explain how tissues taken by biopsy or autopsy can be used to diagnose some
diseases.

LAB ACTIVITY 4

1. Interactive Access. Access your Mastering A&P.

2. Click the Study Area  Practice Anatomy Lab (PAL)  Histology  Explore the TISSUES
3. Reinforce you understanding by accessing PAL 3.1 Flashcards.
4. Compare the different tissue types with the drawings below.

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Take a break and Have a Kitkat!