Biology 241 – Lab
LAB #4
(4th/21 Lab Sessions for Fall Quarter, 2008)
TOPICS TO BE COVERED:
»Continue examining/drawing/labeling various Connective Tissue sub-types, specifically: the three
Cartilages: Hyaline Cartilage C.T., Fibrocartilage C.T., and Elastic Cartilage C.T.
»Examine/draw/label Osseous Connective Tissue
DESIRED OUTCOMES:
After completing the activities described for this lab session, students should:
»Be able to recognize microscopically the 3 cartilage connective tissues, including naming the
predominant cell type (chondrocyte) surrounded by its lacunar space within the lacuna.
»Be able to recognize microscopically and describe the structure known as a perichondrium.
»Be able to recognize microscopically the functional unit of compact bone called an Osteon and
all its structural components
»Be able to differentiate between concentric/circumferential/interstitial lamellae
»Be able to describe the relationship of one osteocyte to another, osteocytic extensions, canaliculi,
and lacunae/lacunar spaces.
»Be able to recognize microscopically and describe the structure known as a periosteum.
»Relate tissue sub-type structural characteristics to the specific functioning of that sub-type.
»Be able to give one (or more) example(s) of where in the body each tissue sub-type is found.
MATERIALS NEEDED:
»Blue Box of prepared microscope slides marked: HISTOLOGY SLIDE SERIES in lab Bench drawer;
specifically Slide #12: Hyaline Cartilage Connective Tissue; Slide #13: Fibrocartilage Connective Tissue, Slide #14: Elastic Cartilage Connective Tissue; Slide #15: Osseous (Bone) Connective Tissue
»Histology Drawing Sheets, pencils, eraser, Histology Drawing Assignment as reference sheets.
»Photographic Atlas, Ch. 3
»Oversized 3-D Model of A Wedge of Compact Bone
Activity #1: Overview of the Cartilage Connective Tissues (classified as “Firm” (Not Rigid, Not Soft) )
Cartilages are classic connective tissues in that their cells, chondrocytes, are widely spaced and there is
lots of intercellular matrix. Basically, the nature of the matrix in cartilages is a network of collagen fibers (and
some elastic fibers) firmly embedded in chondroitin sulfate, a gel-like component of the ground substance.
Cartilage can endure considerably more stress than soft or dense connective tissue sub-types, given the collagen
gives it its strength and the chondroitin sulfate gives it its resilience (ability to recover original size/shape after
deformation, usually caused by a compressive stress).
The “new feature” about the cartilage connective tissue sub-types is that they are avascular – meaning
they lack a direct blood supply. Also, each of the cells (chondrocytes) becomes isolated from the others; and
since diffusion of nutrients is slow, the cells must surround themselves with a bit of fluid that will nourish and
sustain them. The fluid surrounding each chondrocyte is contained by a lacuna, and occupies the lacunar space.
Biology 241 – LAB #4 – continued
Page Two
Now, try to solidly grasp what a lacuna is! It is NOT a structure! It is merely the boundary of matrix that, when
secreted by the chondrocyte, approximates the plasmalemma of the cell but very respectfully positions itself a
tiny distance away from the plasmalemma – as if to give the chondrocyte some “breathing room”. Actually, it is
creating a “space” (the lacunar space) which comes to be occupied by a small bit of nutrient-laden, pH balanced,
life-giving fluid to each cell such that it can carry on its metabolic activities for a long period of time with minimal exchange of substances. When a chondrocyte divides, each of the two new daughter cells starts secreting
matrix (ground substance and protein fibers). As a result, cells “push away” from one another, each one becoming isolated in its own lacuna as it matures. Especially for the Elastic Cartilage C.T. and the Fibrocartilage C.T.,
the lacunae look quite dense (darkly stained), because the protein fibers DO NOT pierce through the lacunae;
rather, they graze the boundary (perimeter) of it and this results in giving the lacunar boundary more strength,
definition, and density.
Note: Be sure to look for the TWO PARTS of a Perichondrium: (1) the inner, deep chondrogenic layer – single
layer of somewhat squamous-looking chondroblasts – that, when called upon to do so, will give rise to new
chondrocytes; and (2) the several thicknesses of cells of the outer fibrous layer – a protective, fibrous connective
tis-sue structure. Hyaline Cartilage C.T. and Elastic Cartilage C.T. have a perichondrium present; Fibrocartilage C.T., the strongest of the three types of cartilage C.T., lacks a perichondrium.
You must draw/label the perichondrium (with its two distinctly visible parts) in at least ONE of your cartilage C.T.
drawings.
Activity #2: Overview of Osseous C.T. – The functional component of Compact Bone: the OSTEON
All Osseous C.T. is described as “lamellar” in that the matrix appears to be laid down in “sheets” or
planes – because that is just the way metabolically active cells behave when all cells are secreting ground
substance and protein fibers at the same rate, they are “pushed away” from one another more or less equidistantly; and this leaves the matrix in between arranged in neat “rows” aka lamellae. Although all bone C.T. is
lamellar, it is further classified as either compact or spongy ( aka trabecular or cancellous), depending on how
its extracellular matrix and cells are organized. The basic unit of compact bone is the Osteon (aka Haversian
system); the basic unit of spongy bone is the Trabecula (Greek for “strut” or “beam”.)
For today, you will examine and generate labeled drawings for Slides #12 - #15 representing the following
four connective tissue subtypes: Hyaline Cartilage C.T.; Fibrocartilage C.T.; Elastic Cartilage C.T.; and
Osseous (aka Bone) Connective Tissue.