Rehab 106 (Pedia) Lecture - BSPT 3 PDF

REHAB 106 (PEDIA) LECTURE BSPT 3 INSTRUCTOR: DANICA BARREDO, PTRP  MODULE 1: INTRODUCTION TO LIFE I. Review of Cell Reproduction & Hormones II. Reproductive cycle III. Fertilization IV. Neurulation & Gastrulation V. Derivatives of the Germ Layer...

REHAB 106 (PEDIA) LECTURE BSPT 3 INSTRUCTOR: DANICA BARREDO, PTRP  MODULE 1: INTRODUCTION TO LIFE I. Review of Cell Reproduction & Hormones II. Reproductive cycle III. Fertilization IV. Neurulation & Gastrulation V. Derivatives of the Germ Layer VI. Clinical Correlates: Birth Defects  A. REVIEW Mitosis Meiosis Same genetic component Contains a single copy of each as parent cell chromosome Diploid Haploid 46 chromosomes 23 chromosomes For growth and repair For reproduction Ex: skin cell, stomach cell Ex: gametes: sperm & egg cell  A. REVIEW Gland / Tissue Hormone Description / Function o 2 main Progesterone o Stimulates secretion of “uterine milk” by the uterine hormones that endometrial glands get the o Promotes development of secretory apparatus of pregnancy breasts happening o Progesterone teams up with relaxin to help soften o Produced by ligaments and cartilage and loosen the joints to the ovaries and prepare you for labor. later by the Estrogen o Responsible for feminine effect. Growth and placenta development of:  Female reproductive system  Female breasts & deposition of fats  Female secondary sexual characteristics o It initiates and regulates a woman’s menstrual cycle o Helps the uterus grow, maintains uterine lining, regulates other key hormones and triggers the development of baby’s organs.  A. REVIEW Gland / Tissue Hormone Description / Function o Produced Follicle o Female: by the Stimulating  Stimulates the release of estrogen and anterior Hormone progesterone pituitary (FSH)  FSH helps control monthly cycle. gland  Stimulates eggs to grow in the ovaries o Male: stimulates release of sperm Luteinizing o Female: Hormone  Triggers the ovulation (LH)  Works in concert with FSH to orchestrate your menstrual cycle  Levels rise just before ovulation o Male: stimulates release of testosterone for masculine effect and protein deposition  B. REPRODUCTIVE CYCLE o It starts at puberty  Ovarian cycle (OFL) Explains what happens in the ovary with the development of the ova  B. REPRODUCTIVE CYCLE o It starts at puberty  Ovarian cycle (OFL) Explains what happens in the ovary with the development of the ova Ovarian Cycle Follicular Phase Luteal Phase o Menstruation to ovulation o Ovulation before menstruation o Describes the status and situation of the follicle (sac that contains the egg) Days 1-14 Days 15-28 o Primordial follicle o The Graafian follicle ruptures o Granulosa o Corpus luteum o Antrum o Corpus luteum degenerates o Graafian follicle o Corpus albicans o Secondary oocyte B. REPRODUCTIVE CYCLE  B. REPRODUCTIVE CYCLE  Uterine cycle It occurs concurrently (at the same time) with the ovarian cycle) Shows how the endometrium changes thickness B. REPRODUCTIVE CYCLE B. REPRODUCTIVE CYCLE C. FERTILIZATION  C. FERTILIZATION o Usually takes place in the uterine tube o Sperm must be introduced into the female reproductive tract FIVE DAYS before ovulation  Sperms are viable for 5 days o Sperm initially incapable of fertilization  Requires capacitation, meaning the tail (flagellum) of the sperm moves faster, causing the plasma membrane to alter  Plasma membrane can fuse with secondary oocyte o Secondary oocyte viable for 12-24 hours  Gets produced in the ovary  It takes 4 days to go to the uterus  It can meet the sperm along the uterine tube o Fertilization happens in the uterine tube o Implantation happens in the uterus  C. FERTILIZATION a. Sperm Penetration of the Secondary Oocyte o From an ejaculation there is ~ 50-500 million sperm, a lot of bunch can reach the secondary oocyte 1. Acrosomal reaction begins 2. Enzymes released 3. Break through zona pellucida  First sperm to bind to the receptor wins  Sperm is then transported to the cytoplasm  The zona pellucida hardens to prevent polyspermy (multiple sperm fertilizing the egg)  C. FERTILIZATION b. Fertilization stimulates Meiosis II Meiosis II o It starts when the sperm fertilizes the secondary oocyte o The secondary oocyte becomes the Ovum What happens? o The membrane of the sperm disintegrates o The chromosomes from the ovum and sperm migrate to the center Zygote o The term for the fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm).  C. FERTILIZATION b. Fertilization stimulates Meiosis II What happens after fertilization? Zygote ↓ Undergoes mitosis ↓ Blastomere – 2-celled stage (30 hrs) ↓ Morula (3-4 days postfertilization) ↓ Blastocyst (4-5 days postfertilization) ↓ Blastocyst becomes an embryo and cells begin to differentiate at this stage ↓ Implantation at the uterus (6 days postfertilization)  C. FERTILIZATION o Morula  Solid ball of cells o Blastocyst  Hollow ball of cells  Becomes an actual embryo  Cells begin to differentiate o Trophoblast  Will eventually develop into placenta  C. FERTILIZATION Case: Twins Monozygotic / Identical twins  Morula divides into 2 forming 2 separate blastocyst  Shared placenta Dizygotic / Fraternal twins  2 different eggs fertilized by 2 different sperms forming 2 different zygotes and 2 different blastocyst  Separate placenta  C. FERTILIZATION c. Implantation of the blastocyst: o The endothelium swells, increasing the glycogen stores  Glucose is the main source of fuel for our cells; stored form of glucose is made up of many connected glucose molecules and is called glycogen o Trophoblast starts secreting enzymes to dissolve away the wall of the endometrium  Dissolves the wall of the endometrium to provide nourishment to the developing embryo o Paracrines are also secreted, which increase the number of capillaries, allowing more oxygen and nutrients into the area  Increase capillaries in the area for more oxygen and remove more carbon dioxide  C. FERTILIZATION c. Implantation of the blastocyst: o At 5 weeks trophoblast thickens → becomes chorion → encapsulates embryo o 8 weeks = resembles a human, called a fetus, placenta is developed o Placenta – allowing exchange of gases and nutrients between fetus and mother; maternal and fetal circulation  D. NEUROLATION & GASTRULATION TION & GASTRULATION o Neurulation  The process where the neural tube forms  About weeks 3-4  Neural tube is important because it will later form the brain, spinal cord, meninges, and bones that surround them (CNS) o Layers of neural tube  Ectoderm  Mesoderm  Endoderm o Gastrulation  Major vent of 3rd week of development  Basically where 3 primary germ layers (ectoderm, mesoderm, and endoderm) form and start becoming different types of tissues.  D. NEUROLATION & GASTRULATION Ectoderm o Will give rise to the nervous system and skin Mesoderm o Actually originates from ectoderm o Will form the connective tissues and also will give rise to bones, muscles, genital organs, pleura, as well as the peritoneal linings of the body cavity Endoderm o Will give rise to the lining of internal organs such as the GI tract and lining of the airways Notochord o Induces neurulation, stops the process of neurulation o Later in life will form as nucleus pulposus of the IV discs  D. NEUROLATION & GASTRULATION FiliPinas Got Crazy Talent Neural Plate  Neural fold + neural groove area Neural Fold  By the end of 3rd week the lateral edges of ectoderm becomes more elevated and will form the neural fold Neural Groove  Depressed midregion Neural Crest Neural Tube  D. NEUROLATION & GASTRULATION *Top view of neural plate o Top = cranial/head  Will give rise to the brain o Bottom = caudal/tail  Will give rise to the spinal cord o Neurulation advances both cranially and caudally; so it starts in the midregion o Eventually the neural folds will approach each other and fuse, thus converting the neural plate essentially into the neural tube  D. NEUROLATION & GASTRULATION o Neural tube can be divided into sections Prosencephalon Cerebrum Thalamus Mesencephalone Midbrain Rhombencephalon Pons Cerebellum Medulla Spinal cord Spine E. DERIVATIVES OF THE GERM LAYER E. DERIVATIVES OF THE GERM LAYER  E. DERIVATIVES OF THE GERM LAYER Mesoderm o MSK Structures  Muscle (smooth, cardiac and skeletal)​  Muscles of the tongue (occipital somites)​  Pharyngeal arches muscle (muscles of mastication, muscles of facial expressions)​  Connective tissue​  Dermis and subcutaneous layer of the skin​  Bone and cartilage​  Dura mater​  Endothelium of blood vessels​  Red blood cells​  White blood cells​  Microglia​  Dentine of teeth​  Kidneys​  Adrenal cortex​  E. DERIVATIVES OF THE GERM LAYER Ectoderm o GI organs / Viscera  Pharynx​  Eustachian tube​  Tonsils​  Thyroid gland​  Parathyroid glands​  Thymus gland​  Larynx​  Trachea​  Lungs​  Gastrointestinal tract (except mouth a nd anus)​  Urinary bladder​  Vagina​  Urethra​  F. CLINICAL CORRELATES: BIRTH DEFECTS DEFECT o Structural, behavioral, functional or metabolic disorders present at birth o Leading cause of mortality rates among infant - 21% o 40-60% idiopathic o 15% of newborns have minor anomalies MALFORMATION o It refers to alteration of normal configuration of a structure o It occurs during formation of structure during Organogenesis (3rd-8th week) – formation of organ system o It may present as partial or complete disruption or absence of a structure o May be caused by environmental or genetic factors acting individually or in concert DISRUPTION o Result in morphological alteration of already formed structures of already formed structures o Caused by a destructive process o Example:  Defects produced by ________________ (restricting bands – usually cause of auto-amputations)  F. CLINICAL CORRELATES: BIRTH DEFECTS DEFORMATION o Result from mechanical forces o Mold a part of fetus over prolonged period o Usually the fetus is compressed inside the amniotic cavity o Example:  Club foot o Often involves MSK structure o May be reversible postnatally SYNDROME o A group of anomalies that are occurring together o Specific common cause o Diagnosis in itself o Risk of recurrence is known o Example: Down Syndrome  Higher risk if mother is already at age 35-40 and above upon giving birth ASSOCIATION o Nonrandom appearance of two or more anomalies o Occur together more commonly than by chance alone o Cause has not been determined yet o Example: VATER/VACTERL association  Vertebral anomalies  Anal atresia  Cardiovascular anomalies  Tracheosophageal fistula  Esophageal atresia  Renal and/or radial  F. CLINICAL CORRELATES: BIRTH DEFECTS Periods of Susceptibility to Abnormal Development o The result of many investigations have allowed the following generalization  Insults to the embryo during the first 3 weeks of embryogenesis (the early period before organogenesis begins) are unlikely to result in defective development because they either kill the embryo or are compensated for by the powerful regulatory properties of the early embryo  The period of maximal susceptibility to abnormal development occurs between weeks 3 and 8, the period when most of the major organs and body regions are first established  F. CLINICAL CORRELATES: BIRTH DEFECTS Causes of Malformation o Despite the considerable research since the 1960s, the cause of at least 50% of human congenital malformations remains unknown o Roughly 18% of malformations can be attributed to genetic causes (chromosomal defects based on mendelian genetics) o 7% of malformations are caused by environmental factors, such as physical or chemical teratogens o 25% are multifactorial, for example, caused by environmental factors acting on genetic susceptibility.  F. CLINICAL CORRELATES: BIRTH DEFECTS Developmental Disturbances Resulting in Malformations o Duplication and Reversal of Asymmetry ✓ The classic example of duplication is identical twinning ✓ Under normal circumstances, both members of the twin pair are completely normal, but rarely the duplication is incomplete, and conjoined twins result  F. CLINICAL CORRELATES: BIRTH DEFECTS Developmental Disturbances Resulting in Malformations o Faulty Inductive Tissue Interactions ✓ Absent or faulty induction early in development (e.g. induction of the CNS) is incompatible with life, but disturbances in later inductions can cause malformations ✓ Absence of the lens (aphakia) or of a kidney (renal agenesis) can result from an absent or abnormal inductive interaction  F. CLINICAL CORRELATES: BIRTH DEFECTS Developmental Disturbances Resulting in Malformations o Absence of a Normal Cell Death o Failure of Tube Formation o Disturbances in Tissue Resorption o Failure of Migration o Developmental Arrest o Hypoplasia and Hyperplasia o Receptor Defects o Effects Secondary to Other Developmental Disturbances o Germ Layer Defects