Exam 2 Review and Osseous Tissue

Exam 2 Review

  • Average score: 80%
  • Kahoot extra credit: Additional 3.83% added to final grade.
    • Value based on student scores; varies between 2-5%.
    • Not everyone attempted the Kahoots.
    • Opportunity for practice and extra credit.

Glycocalyx Functions

  • Question on Exam 2: "The glycocalyx serves which of the following functions? (Check all that apply.)"

    • Correct answers (all):
      • Defense against cancer: Cancer cells alter glycocalyx properties, allowing immune system recognition.
      • Fertilization: Guides sperm to the egg.
      • Adhesion: Helps bind cells together.
      • Transplant compatibility: Determines blood type (A, B, AB, O).
      • All points were awarded for this question.

Transcription vs. Translation

  • Question on Exam 2:
    • Transcription produces messenger RNA (mRNA).
    • Translation produces a polypeptide (protein).
    • The question was dropped due to many incorrect answers.

Diffusion and Facilitated Diffusion

  • Diffusion and facilitated diffusion can occur in either direction across the cell membrane.
  • These forms of transport are gradient-dependent, not direction-dependent.
  • True statement; diffusion can occur into or out of the cell depending on the concentration gradient.

General Information

  • Week 2 lab scores are posted online.
  • Course exams: 100 points.
  • Weekly labs: 25 points total.
  • Report any grade book problems ASAP.

Upcoming Exam

  • Next exam: Monday, open from 7 AM to 7 PM.
  • Labs due: All labs for the week due by 7 AM on Monday.

Epidermis Strata

  • Mnemonic: "Bro. Seriously Gotta Love Cats."
    • Basale
    • Spinosum
    • Granulosum
    • Lucidum
    • Corneum

Stratum Details

  • Basale:

    • Stem cells (replenish skin)
    • Melanocytes (pigment producing cells)
    • Tactile cells
    • Everyone has relatively the same number of melanocytes; pigment type determines skin color.

  • Spinosum:

    • Keratinocytes (most abundant)

  • Granulosum:

    • Keratinocytes filled with granules of keratin (speckled cytoplasm).

  • Lucidum:

    • Only in thick skin (palms and soles)
    • Dead keratinocytes without organelles

  • Corneum:

    • Dead keratinocytes, shed via exfoliation (house dust).

Skin Cancer Origins

  • Named based on the skin cell of origin.

    • Basal Cell Carcinoma:

      • Origin: Stem cells of stratum basale.
      • Generally treatable, slow-moving; doesn't tend to metastasize.

    • Squamous Cell Carcinoma:

      • Origin: Keratinocytes of stratum spinosum.
      • Can metastasize to tissue layers below.

    • Malignant Melanoma:

      • Origin: Melanocytes in stratum basale.
      • Often derived from a pre-existing mole.
      • Spreads easily (metastasizes).

Sunscreen Reminder

  • Apply sunscreen often.
  • Oxidative stress from UV exposure starts approximately 30 minutes after application.

Glands and Other Skin Structures Reminder

  • Apocrine and merocrine sweat glands; sebaceous (oil) glands.
  • Ceruminous (earwax) glands; mammary glands (discussed later in female reproductive unit).
  • Structures of hair and abnormal skin colors.

Osseous Tissue: Introduction to the Skeletal System

Compact Bone

  • Tough tissue that supports body weight.
  • Muscles insert into bones and use them as pulleys for movement.
  • Structural unit: Osteon
    • Multiple layers of hardened, mineralized matrix (lamellae)
    • Living bone cells (osteocytes) in spaces (lacunae) between lamellae.
    • Local blood and lymphatic and nerve supply.
    • Central canal: Passageway for blood vessels and nerves, runs lengthwise.

Osseous Cells

  • Three types:

    • Osteoblasts: Bone synthesizing cells (bone formation).
    • Osteoclasts: Dissolve bone (bone resorption).
    • Osteocytes: Can both synthesize and reabsorb bone; located in lacunae as mature bone cells.

  • Bone is constantly being built up and broken down throughout life based on stresses.

Detailed Look at Osteons

  • Neighboring osteons are the structural units of compact bone.

  • Central Canal. It is the most prominent feature:

    • Contains blood and nerve supply.

  • Concentric Lamellae:

    • Multiple layers surrounding the central canal.

  • Lacunae:

    • Reservoirs for cells wedged between lamellae.

  • Canaliculi:

    • Tiny canals connecting lacunae, where osteocytes receive nourishment

Long Bone vs. Flat Bone Anatomy

  • Long Bones: Primarily for movement, muscles contract on them to create motion.

  • Flat Bones: Primarily for protection, covering vital organs.

Long Bone Anatomy

  • Diaphysis: Medial shaft

  • Epiphyses: Enlarged ends (proximal and distal)

  • Articulating Cartilage: Covering on each end (joint surface)

  • Periosteum: Superficial covering

  • Endosteum: Inner lining of marrow cavity

  • Bone Marrow:

    • Yellow bone marrow: Located mostly in the diaphysis (shaft) and is mostly fat and inactive.
    • Red bone marrow: Located in the proximal epiphyses and produces all the constituents of the blood. (red blood cells, all of our white blood cells, even our platelets)
    • Adults maintain red bone marrow in the head of the femur, humerus, and bones of the torso
    • When you're kids, all of your bones are filled with red bone marrow. But as you become adults, the bone marrow of the limbs turns to the inactive form.

  • Epiphyseal Plate/Line:

    • Where long bone growth occurred; fuses into the epiphyseal line once full height is achieved.

Flat Bone Anatomy

  • Two layers of compact bone (outer and inner) consisting of osteons.

  • Middle layer: Spongy bone (lattice network with holes).

  • Trabeculae: Resist force within spongy bone; dissipates pressure, protecting the inner layer of compact bone.

Bone Cancer

  • Bone cancer can affect any part of the bone and originates from osteoblasts, osteoclasts, or osteocytes.
  • Tumor formation occurs where these cells become cancerous.
  • If cancer develops in the bone marrow, it results in blood cancer.

Intramembranous Ossification (Flat Bone Development)

  • Stage 1: Condensation of mesenchyme with blood infiltration.

  • Stage 2: Osteoblasts produce bony matrix (osteoid tissue, not yet mineralized).

  • Stage 3: Development of spongy bone; bony arms of trabeculae form, and spaces fill with bone marrow.

  • Stage 4: Compact bone forms an inner and outer layer, a middle layer of spongy bone, and an outer periosteum covering.

Endochondral Ossification (Long Bone Development)

  • Embryonic skeleton first formed out of hyaline cartilage.

  • Primary ossification occurs. That means the first infiltration of bone comes in the center, so that would be in the diaphyses. A bony collar almost like a napkin ring forms.

  • Secondary ossification occurs. With further development that collar transitions to become the primary marrow cavity of bone. As that develops, the secondary ossification center then is developing on the ends, on the epiphyses.

  • At Birth. The Bone is mostly cartilage, right? The secondary formation becomes the hollowed out cavities.

  • Long bone growth is achieved during childhood at that epiphyseal plate but it doesn't last and can't happen forever.That plate, once someone achieved full height, that remains and can still be evident with examination, as the epiphyseal line.

Fractures

  • Stress Fracture: From a large force, accident, trauma, wear and tear.

  • Pathological Fracture: Result from diseases of the bone (osteoporosis, cancer).

  • Open Fracture: Penetrates the skin; typically displaced.

  • Closed Fracture: Soft tissue remains intact, but can still be displaced.

  • Greenstick Fracture: Common in pediatric patients due to bone not fully hardened. Fracturing one end of the bone, but not all the way through the bone.

  • Comminuted Fracture: Bone shatters, creating a gap that requires surgery and support.

  • Linear Fracture: May require a casting to keep it immobile.

  • Transverse Oblique Fracture: Nondisplaced fracture that requires alignment for healing.

  • Spiral Fracture: Not abuse always is, but can be strongly associated with abuse.

  • Colles' Fracture: Common fall injury to the ends of the forearm's long bones.

  • Pott's Fracture: Ends of the long bones of the leg/common sports injury.

Bone Remodeling and Calcium Homeostasis Regulation

  • Three hormones play a role in calcium balance: calcitriol (vitamin D), parathyroid hormone, and calcitonin.

Blood Calcium Level Summary:

  • Blood Calcium Location: Calcium is in our bodies, although most of it is located in skeleton, there's some blood calcium levels.

  • Calcium Introduction: When we feed ourselves we are able to ingest calcium to our bodies.

  • Calcium Excretion: As we get rid of stuff through feces, and what is excreted in the urine.

Hormone Regulation of Blood Calcium Levels

Calcitriol (Activated Vitamin D)

  • Stimulus: Hypocalcemia (low blood calcium levels).

  • Targets:

    • Digestive Component: Enhances calcium absorption from the digestive tract into the blood.
    • Kidney: increasing reabsorption of calcium by the kidney
    • Skeleton. This allows more bone for break down, that frees up, and releases calcium in the mineral heart to the blood: Osteoclasts (bone dissolving) activity.

  • Results: Increase blood calcium levels back to normal.

Parathyroid Hormone (PTH)

  • Stimulus: Hypocalcemia (low blood calcium levels).

  • Targets:*

    • Urinary system: enhances how much is absorbed by the kidney.
    • The Skeleton. This allows more bone for break down, that frees up, and releases calcium in the mineral heart to the blood: Osteoclasts (bone dissolving) activity.

  • Results: Overall end result; brings blood calcium levels back to normal.

Calcitonin

  • Stimulus: Hypercalcemia (elevated blood calcium levels; basically, you're having a spike)

  • Targets: Only Targets the bone. Enhance Bone building (stimulating the osteoblasts) and those are the bone markers.

  • Results: By making more bone, or adding more minerals, that's going to lower the blood calcium availability. Again, hopefully, back to what is normal.

Potential Exam Question/Application

  • In Both Scenarios, how would you elevate the high and low levels to correct for the high blood calcium levels?

Cell Action

  • How could we have elevated the Bone Activity, to help with low blood Calcium levels: Osteoblasts, osteoclasts, or osteocytes?
    • Anwser: Majority of you answered osteoblasts. Yes, absolutely true. The osteoblasts, those are having a blast and making the bone making bone, so that means the other class would just be further amplify, right, this imbalance on the bones. So like, if I could have made this multi answer only, both auto blocks, as well as oxides would be correct (with all site being correct.

Hormone Action

  • How could we activate, elevated, again, blood calcium levels? Which one, which hormone what would help lower what would help those brought the levels go back to normals?
    • Majority of you would get most of you guys got that one right. That is calcitonin yes; so that would be the hormone that want to use to correct elevated levels. Excellent. The other two hormones.