Related Experiment Video
Updated: Jul 29, 2026
07:10
Femoral Bone Marrow Aspiration in Live Mice
Published on: July 5, 2014
Comparative morphology of the marrow sac
L X Bi1, D J Simmons, H K Hawkins
1Department of Orthopaedic Surgery and Rehabilitation, University of Texas Medical Branch, Galveston, Texas 77555-0892, USA. lbi@utmb.edu
The Anatomical Record
|November 14, 2000
Summary
Marrow sacs, crucial for bone cell compartmentalization, exhibit species-specific morphologies across vertebrates. Electron microscopy revealed distinct structural variations in these fibroblast-like cell layers.
Area of Science:
- Skeletal Biology
- Comparative Anatomy
- Cell Biology
Background:
- Marrow sacs are cellular structures within the bone marrow.
- Their role in compartmentalizing bone cells is not fully understood.
- Previous studies have lacked detailed comparative morphological analysis.
Purpose of the Study:
- To investigate and compare the morphologies of marrow sacs across different laboratory species.
- To elucidate the structural characteristics of marrow sac cells using advanced microscopy.
- To determine if marrow sac morphology is conserved or species-specific.
Main Methods:
- Utilized scanning electron microscopy (SEM) and transmission electron microscopy (TEM).
- Examined marrow sacs from various laboratory species including rats, cats, sheep, rabbits, and pigeons.
- Analyzed cell arrangement, intercellular connections, and ultrastructural features.
Main Results:
- Marrow sacs consist of overlapping fibroblast-like stromal cells, compartmentalizing osteoblasts.
- SEM revealed seamless, squamous epithelium-like sacs in rats, cats, and sheep.
- Rabbit and pigeon sacs showed a woven, multilayered fabric with numerous intercellular processes.
- TEM indicated attenuated cells with sparse organelles; junctions were absent.
- Sac thickness varied, with rabbits and pigeons having multilayered sacs (3-4 cells deep).
Conclusions:
- Marrow sacs are common components of the vertebrate skeleton.
- Significant species-specific morphological variations exist in marrow sacs.
- The absence of tight junctions suggests a dynamic rather than a rigid barrier function.
Related Concept Videos
01:55Bone Structure
Within the skeletal system, the structure of a bone, or osseous tissue, can be exemplified in a long bone, like the femur, where there are two types of osseous tissue: cortical and cancellous.
01:17Gross Anatomy of Bone
The two main features of a long bone are the diaphysis and the epiphysis.
The diaphysis is the tubular shaft that runs between the proximal and distal ends of the bone. The walls of the diaphysis are composed of dense and hard compact bone made of numerous osteons — the functional unit of the compact bone. The hollow region in the diaphysis is called the medullary cavity, which harbors the bone marrow. In infants and children, this marrow cavity is filled with red marrow, whereas in adults, it...
The diaphysis is the tubular shaft that runs between the proximal and distal ends of the bone. The walls of the diaphysis are composed of dense and hard compact bone made of numerous osteons — the functional unit of the compact bone. The hollow region in the diaphysis is called the medullary cavity, which harbors the bone marrow. In infants and children, this marrow cavity is filled with red marrow, whereas in adults, it...
01:26Bone Markings
Bones have various surface features that help form joints and attach to other soft tissues. Depending on the function, bone markings are categorized into articulating projections, processes for attachment, depressions, and openings.
Articulating Projections
Articulating projections are found where two bones meet to form a joint. These structures are usually found at the ends of bones. The largest articulation is a rounded projection called the head, supported by a narrow neck at the ends of...
Articulating Projections
Articulating projections are found where two bones meet to form a joint. These structures are usually found at the ends of bones. The largest articulation is a rounded projection called the head, supported by a narrow neck at the ends of...
01:09Spongy Bone
All bones comprise an outer layer of compact bone, and an interior made up of spongy bone tissue, also called cancellous or trabecular bone. In long bones, spongy bone tissue is mainly found in the interior of the epiphyses (broad ends of the bone).
Spongy bone is more porous, and less dense compared to compact bone. It is composed of concentric lamellae that are arranged irregularly to form the trabecular network. In some bones, the spaces between trabeculae contain red marrow, where...
Spongy bone is more porous, and less dense compared to compact bone. It is composed of concentric lamellae that are arranged irregularly to form the trabecular network. In some bones, the spaces between trabeculae contain red marrow, where...
01:24Bone Formation by Endochondral Ossification
Bone formation, or ossification, begins around the sixth to seventh week of embryonic development. Most bones develop from a cartilaginous template through the process of endochondral ossification. Cartilage formation begins when clusters of mesenchymal cells differentiate into chondrocytes. These chondrocytes proliferate rapidly and secrete an extracellular matrix that becomes encased in a membrane called the perichondrium. The resulting cartilage model provides a template that resembles the...
01:15Development of the Lymphatic System
The development of lymphatic tissues and vessels in embryonic life begins around the fifth week. These structures originate from the mesoderm layer, with lymph sacs emerging from developing veins.
The first lymph sacs to form are the paired jugular lymph sacs located at the junction of the internal jugular and subclavian veins. From these sacs, lymphatic capillary plexuses extend to the thorax, upper limbs, neck, and head, eventually forming lymphatic vessels. Each jugular lymph sac maintains a...
The first lymph sacs to form are the paired jugular lymph sacs located at the junction of the internal jugular and subclavian veins. From these sacs, lymphatic capillary plexuses extend to the thorax, upper limbs, neck, and head, eventually forming lymphatic vessels. Each jugular lymph sac maintains a...