There are resident (fixed) and wandering cells in CT proper
Resident cells include fibroblasts, adipocytes, fixed macrophages and mesenchymal cells (embryonic stem cells)
Wandering cells include mast and plasma cells, free macrophages and leukocytes
1. Collagen fibers - long, unbranching, strong, flexible and resistant to stretching.
2. Elastic fibers - thinner than collagen, stretch easily, branch and rejoin. These fibers allow structures such as blood vessels to stretch and relax
3. Reticular fibers - thinner than collagen fibers, form a meshwork-like configuration, found in organs with abundant spaces such as liver, lymph nodes and spleen.....packing material
The medulla oblongata, the most inferior part of the brainstem, is formed from the myelencephalon.
• All communication between the brain and spinal cord involves tracts that ascend or descend through the medulla oblongata.
• Within the medulla oblongata are cranial nerve nuclei associated with the vestibulocochlear (CN VIII), glossopharyngeal (CN IX), vagus (CN X), accessory (CN XI), and hypoglossal (CN XII) cranial nerves.
• Connection between brain and spinal cord
• Relays sensory info to thalamus and portions of brain stem
• Contains several autonomic nuclei, which group to form:
o Cardiac center: Regulates heart rate and its strength of contraction
o Vasomotor center: Controls blood pressure by regulating contraction and relaxation of smooth muscle in walls of arterioles
o Medullary respiratory center: Regulates respiratory rate; rate and depth of breathing
• Other nuclei involved in coughing, sneezing, salivation, swallowing, gagging, and vomiting
Is the second largest part or region of the brain.
o 10% of volume but 50% of neurons
• Develops from the metencephalon.
• Has a complex, highly convoluted surface covered by a layer of cerebellar cortex made of folds called folia.
• Composed of left and right cerebellar hemispheres.
• Separated from cerebrum by transverse fissure
• Each hemisphere consists of two lobes, the anterior lobe and the posterior lobe, which are separated by the primary fissure.
• Along the midline, a narrow band of cortex, the vermis, separates the left and right cerebellar hemispheres.
o The vermis receives sensory input the torso position and balance.
o Its' output to the vestibular nucleus helps maintain balance.
• The cerebellum is partitioned into three regions:
1. An outer gray matter layer of cortex.
2. An internal region of white matter, called the arbor vitae.
3. Cerebellar nuclei in the deepest layer.
• Coordinates and fine-tunes skeletal muscle movements and ensures that skeletal muscle contraction follows the correct pattern leading to smooth, coordinated movements.
• Coordinates repetitive body movements
• Coordinates complex learned, somatic motor patterns
o e.g., ride a bike, swing a bat
• Stores memories of previously learned movement patterns.
• Adjusts skeletal muscle activity to maintain equilibrium and posture.
• Receives proprioceptive (sensory) information from the muscles and joints and uses this information to regulate the body's position.
o Monitors the position of each body joint and its muscle tone.
Respond to physical distortion, e.g., touch, pressure, vibration and proprioception
• Mechanically-regulated ion channels
• Open and close in response to stimuli that distort cell membranes
o e.g., Stretching, compression, twisting, etc.
• Also Found in sensory receptors (touch, pressure, vibration)
Small, round or oval structures located along the pathway of lymph vessels
• Typically found in clusters
• The primary function of a lymph node is to filter antigens from the lymph and initiate an immune response
• Most apparent lymph node clusters occur as:
o Axillary lymph nodes
o Inguinal lymph nodes
o Cervical lymph nodes
• Lymph nodes are located:
o Back of head, draining scalp
o Around the neck muscles, draining the back of the tongue, pharynx, nasal cavities, and the roof of the mouth.
o Under the floor of the jaw, draining the floor of the mouth.
o Upper extremities, in the bend of the elbows, under the armpit, and under the pectoral muscle.
o Abdomen and pelvis, along the blood vessels in these regions.
o Lower extremities in back of knee and the groin.
Structure of Lymph Nodes
• Surrounded by a tough connective tissue capsule
• Trabeculae project into the node
• Lymphatic cells surround the trabeculae and lymphatic sinuses provide a pathway for lymph flow
• Have an outer cortex and inner medulla
o Cortex - contains nodules and sinuses called cortical sinuses
o Medulla - contains medullary cords and medullary sinuses
The teeth are collectively known as the dentition
o Responsible for mastication, the first part of the mechanical digestion process
• Have an exposed crown, a constricted neck and one or more roots that fit into dental alveoli
• Each root is enclosed within (covered) harden material called cementum
• Dentin forms the primary mass of the tooth.
o It is harder than bone and deep to cementum and enamel
• The external surface of the dentin is covered with a layer of enamel that forms the crown of the tooth
o Hardest substance in body!
• The center of the tooth is a pulp cavity that contains connective tissue called pulp
• A root canal opens into the connective tissue through an opening called the apical foramen.
o Blood vessels and nerves pass through this opening and are housed in the pulp
• Two sets of teeth develop and erupt in a normal lifetime:
o Deciduous teeth erupt between 6-30 months, are 20 in number, and are often called milk teeth
o Permanent teeth replace the deciduous teeth and are 32 in number
• The more anteriorly placed permanent teeth tend to appear first, followed by the posteriorly placed teeth.
• Incisors: most anteriorly placed, shaped like chisels whose sharp edges bite off large pieces of food and have a single root
• Canines: posterolateral to the incisors, pointed tips for gasping, puncturing, and tearing food
• Premolars: posterolateral to canines, have flat crowns with prominent ridges called cusps for crushing and grinding
• Molars: thickest and most posterior teeth, also adapted for crushing and grinding of ingested materials
• The last teeth to erupt are the third molars, often called "wisdom teeth," in the late teens or early 20's.
• Often the jaw lacks space to accommodate these final molars, and they may either emerge only partially or grow at an angle and become impacted.
• Impacted teeth cannot erupt properly because of the angle of their growth.